Speaker 1: Brought to you by the reinvented two thousand twelve Camray.
Speaker 1: It's ready. Are you get in touch with technology with
Speaker 1: tech Stuff from how stuff works dot com. Hello everyone,
Speaker 1: and welcome to tech stuff. My name is Chris Poulette
Speaker 1: and I am an editor how stuff works dot com.
Speaker 1: The guy sitting across from me, he is Jonathan STRICKLANDUS
Speaker 1: senior writer at how stuff works dot com. Hey there,
Speaker 1: So today we wanted to talk a little bit about
Speaker 1: solid state drives and what makes them work and how
Speaker 1: they are different from the traditional forms of storage media
Speaker 1: that we are used to in the world of computers. Now,
Speaker 1: some of you out there may be used to solid
Speaker 1: state drives, and so you're thinking how our solid state
Speaker 1: drives different from other solid state drives. That's not what
Speaker 1: I mean. I mean those of us who have used
Speaker 1: hard disks that use magnetic storage in some form, and uh,
Speaker 1: there are a lot of differences, mainly mechanical physical differences,
Speaker 1: because when you're talking about a hard disk, I guess
Speaker 1: a traditional hard hard disk drive, you're talking about a
Speaker 1: device that has moving parts and um it has platters
Speaker 1: that are that have information stored on the magnetically use
Speaker 1: magnetic fields to change uh, informations into zeros and ones,
Speaker 1: those bits that we use to create the data that
Speaker 1: computers can understand. And you have a physical device that
Speaker 1: reads that information off of the platters the players have
Speaker 1: to spin for this to happen. Uh. Turns out those
Speaker 1: devices they take up, they take a lot of time
Speaker 1: to pull that information up. Relatively speaking. When I say
Speaker 1: a lot of time, we're talking milliseconds. But still, yeah,
Speaker 1: there are when you think about getting information into and
Speaker 1: out of uh your computers, basically what you're doing right now.
Speaker 1: There there are several different ways it does that. There's uh,
Speaker 1: some information that is available for you know, ready retrieval. Um.
Speaker 1: You know, in the cash that's built in you have
Speaker 1: level one level two cash. You may not have necessarily
Speaker 1: known what that was. I didn't uh you know, and
Speaker 1: it's sort of uh, it's sort of intuitive when you
Speaker 1: think about it. It keeps it this information in this
Speaker 1: cash on hand, so stuff that you're doing right now
Speaker 1: is kept right there close by in a very fast
Speaker 1: um uh in a very fast retrieval system so that
Speaker 1: I can pull it back at at at a nanoseconds. Notice,
Speaker 1: right in fact, if we if we go. It's easy
Speaker 1: to imagine this if we think of the CPU first.
Speaker 1: Just look at the central processing US of your computer
Speaker 1: and think of that as this is the place where
Speaker 1: operations are executed upon data. Right. Yeah, it pulls data in,
Speaker 1: it executes an operation on it, it gets a result.
Speaker 1: That's the purpose of the CPU. Now, CPU has something
Speaker 1: called registers. Registers are where the CPU can hold data.
Speaker 1: But registers hold a very small amount of data comparatively speaking,
Speaker 1: usually just a few hundred bytes. You can build larger registers,
Speaker 1: and you can build more registers for your CPU, but
Speaker 1: that tends to be pretty expensive. Now, the benefit of
Speaker 1: having information and registers on the CPU is that you
Speaker 1: have next to no time at all between when you
Speaker 1: pull the information and when you can execute an operation
Speaker 1: upon that information. So that means that we say that
Speaker 1: the latency for the information within a CPUs registers is zero.
Speaker 1: Latency is that time between when you retrieve information and
Speaker 1: when you can or when you send a request for
Speaker 1: information and when you actually retrieve it. Yes, so there's
Speaker 1: no latency when you're talking about a the CPUs registers. However,
Speaker 1: only a few hundred bytes are exist within those registers.
Speaker 1: It's not a lot of data. Now you were talking
Speaker 1: about the cash is the level one cash is kind
Speaker 1: of the information that the CPU uses frequently. It's going
Speaker 1: to in whatever application you have to be in at
Speaker 1: that time, right, So this is information that the CPU
Speaker 1: is having to go to again and again, and it
Speaker 1: needs it to be as close as possible so that
Speaker 1: it keeps that latency down because of course, if you
Speaker 1: have to go further out for your information, it's going
Speaker 1: to take longer for it to get back. So at
Speaker 1: level one cash, you're talking about around bytes of data
Speaker 1: per CPU core if you're running an ivy Bridge processor
Speaker 1: and I seven core ivy Bridge processor from Mentel, so
Speaker 1: that's thirty bytes per uh core and as far as
Speaker 1: that level one cash goes and that takes a nanosecond
Speaker 1: to pull that data up, So that's one billionth of
Speaker 1: a second. Yep, and uh you know, just on the
Speaker 1: just to comment on the ivy Bridge note, the cash
Speaker 1: is themselves, um you know they exist on all these
Speaker 1: different processors. That's just that figure just specific to the
Speaker 1: ivy Bridge, but other processors do have this as well. Yes,
Speaker 1: just in case there was any confusion, and and then
Speaker 1: you could have a level to cash, which is slightly
Speaker 1: further out, you know, think of think of it like
Speaker 1: concentric circles, right, So the level two cash is a
Speaker 1: concentric circle further out from the CPU. It can hold
Speaker 1: a little more data. It's a little slower to pull
Speaker 1: that information up, it's a few nano seconds. Then it
Speaker 1: may even have a level three cash. Not all CPUs do,
Speaker 1: but many do. And then that is even larger and
Speaker 1: holds even more data and takes even longer again in
Speaker 1: relative terms, to get that data to the CPU. And
Speaker 1: beyond that, that's when you go to your computer's actual memory,
Speaker 1: because all the stuff we've been talking about right now
Speaker 1: is all located on the CPU die itself. So it's
Speaker 1: all part of that that chip. Yeah, it's not you know,
Speaker 1: it's not separate. It's on another element that's on the motherboard.
Speaker 1: This is all part of the CPU. Yeah. If you
Speaker 1: if you pull your hard drive out of the computer
Speaker 1: toss it on the floor, don't don't do that. Um.
Speaker 1: And uh, and you you pull the RAM chips out
Speaker 1: of your computer and toss them on the floor, don't
Speaker 1: do that either. Um. Then I'm glad you did that
Speaker 1: because I was thinking it it was just funny that
Speaker 1: you said it. Um, then the uh, the registry and
Speaker 1: the cashes will still be there on the computer and
Speaker 1: I won't be able to do a whole lot with them.
Speaker 1: But still, um, so you know that, just to illustrate that.
Speaker 1: So yes, the next part we'll we'll pick this stuff
Speaker 1: gently back up off the floor and put it inside
Speaker 1: the RAM is essentially the next ring out if you will,
Speaker 1: from the cashes. However, many that you happen to have
Speaker 1: on your CPU, right, and these these memory chips have
Speaker 1: been optimized so that the latency is really really low. However,
Speaker 1: they are not located on the CPU. No, they are
Speaker 1: connected by circuits by by pathways to the CPU. Well,
Speaker 1: because they are not located on the CPU, and because
Speaker 1: that information does have to actually travel a physical distance,
Speaker 1: that increases the latency time. So when your CPU has
Speaker 1: to pull information out and that information is not in
Speaker 1: the cash for the CPU, it has to but it
Speaker 1: resides within the memory of your computer, then it has
Speaker 1: to travel this pathway and for the the request and retrieval,
Speaker 1: that can take between forty and eighty nanoseconds. So we're
Speaker 1: still talking a fraction of a second. Yeah, I mean
Speaker 1: this is These are are times that you or I
Speaker 1: will not even be able to notice. Yeah, we can't.
Speaker 1: We we have no ability to to register that using
Speaker 1: our senses. We would have to use incredibly sensitive measurement
Speaker 1: devices in order to be able to tell the difference
Speaker 1: between forty and eighty nanoseconds. To us, there's no meaningful
Speaker 1: difference at But the uh. But the thing about RAM
Speaker 1: is when you shut off the computer, all that information
Speaker 1: that's in RAM disappears. Yeah, it's it's held there by
Speaker 1: the electrical charge UM, which is relative to the computer.
Speaker 1: Now you're hard drive with the information stored we're talking
Speaker 1: traditional with the information stored manet magnetically on those platters. UM,
Speaker 1: it's able to save that stuff so that when you
Speaker 1: turn the computer back on, you can read the hard
Speaker 1: drive and get it back. UM. The thing is that
Speaker 1: hard drives have different rotating speeds UM. Typical to see
Speaker 1: a laptop with a rpm uh drive or or even
Speaker 1: revolutions per minute just in case you aren't familiar with
Speaker 1: the term UM, and you're more likely to see fat
Speaker 1: those and faster in desktop computers. UM. And the faster
Speaker 1: these rotate in general, that means the faster the information
Speaker 1: can be pulled from the hard drive and sent to
Speaker 1: memory and then onto your CPU. UM. So if you
Speaker 1: if you took your hard drive, the thing is that
Speaker 1: these systems are are delicate their their machine to very
Speaker 1: precise tolerances. That the head um that reads the disk,
Speaker 1: it looks like it looks like a record player for
Speaker 1: those of us who remember that, but the the head
Speaker 1: doesn't actually touch the disc. If it does, that's what
Speaker 1: they call a bad thing. Yeah, it looks like it's
Speaker 1: in contact because it's so close to the platter, but
Speaker 1: in actuality there is like a millimeter's difference between where
Speaker 1: it is or even less. It's amazing. And that's the thing.
Speaker 1: If you did take your if you did take your
Speaker 1: hard drive and throw it on the floor, it is
Speaker 1: very possible that the head crashed into the platters, which
Speaker 1: is very bad. Right. If you ever hear a clicking
Speaker 1: noise from your hard drive, that usually means that the
Speaker 1: platters are out of alignment, or that the head is
Speaker 1: actually coming into contact, something is hitting against something else
Speaker 1: with then that physical mechanical device, and that means that
Speaker 1: it is breaking down. That that also means you should
Speaker 1: take that hard drive as soon as you can to
Speaker 1: a professional who can pull the data off of the
Speaker 1: hard drive, because the hard drive itself may or may
Speaker 1: not be uh you may or may not be able
Speaker 1: to repair it. So you definitely want to be able
Speaker 1: to retrieve the information. And the reason why we're even
Speaker 1: talking about this physical device is because you may have guessed,
Speaker 1: because you've got this mechanical element, it's going to take
Speaker 1: a lot longer to retrieve that information. Comparatively speaking, we're
Speaker 1: talking about milliseconds now as opposed to nanoseconds, and in
Speaker 1: the world of computers, that's a long time. You know,
Speaker 1: you're talking about these other fractions of a second, billions
Speaker 1: of a second and then several or you know, you
Speaker 1: go to a couple orders of magnitude up you realize
Speaker 1: this is this is a lot longer, and it's going
Speaker 1: to mean that in general, the operations that you start
Speaker 1: to use on your computer are going to take more
Speaker 1: and more time. Well, there are only so many ways
Speaker 1: we can limit how much time it takes to retrieve
Speaker 1: information from a hard drive. Some of that includes creating
Speaker 1: better interfaces, which is when we went from the two
Speaker 1: SATA interfaces s A T A interfaces. Uh, that was
Speaker 1: actually a big improvement. It meant that we could move
Speaker 1: data much more quickly from the hard drive into RAM.
Speaker 1: But there's only so so much faster you can go
Speaker 1: without really turning up that RPM speed to ludicrous amounts.
Speaker 1: And of course the faster it goes, the more likely
Speaker 1: you have mechanical problems down the line. I mean we're
Speaker 1: and tear and things of that nature. So, um, you
Speaker 1: have the incredibly reliable hard drive. I mean we've been
Speaker 1: using these things for years and years now. Um, they've
Speaker 1: gone up to very large sizes. Uh. And and they're
Speaker 1: they're fairly cheap compared to the way they were just
Speaker 1: a few years ago. But they have they have their
Speaker 1: own problems. I mean they're they're delicate. You can't necessarily
Speaker 1: take them everywhere, um, you know, and expect them to
Speaker 1: operate uh flawlessly. Um and uh you know, as you
Speaker 1: pointed out, they're they're only so fast. So uh. Flash
Speaker 1: memory in general is is, you know, an alternative, a
Speaker 1: very pleasant alternative. It works in our in our smartphones
Speaker 1: and our music players. Um, it works in in memory sticks,
Speaker 1: I mean thumb drives. You know, kids of all ages
Speaker 1: now take them to school with them because you know,
Speaker 1: that you can keep. Um I remember one gigabyte hard
Speaker 1: drives that were huge, and now you can keep sixteen
Speaker 1: gigs on a tiny thumb drive that cost you know,
Speaker 1: a very tiny fraction of the price. Spies. Spies use
Speaker 1: them to UH to put malware onto secure systems. Because
Speaker 1: both both stucks net and Flame appear to have been
Speaker 1: injected into target computers using UH and an off site
Speaker 1: sort of storage device. So some sort of well offsite
Speaker 1: from the computer system UH so something like a thumb drive.
Speaker 1: So you can imagine there's a guy who might have
Speaker 1: paid a little visit to an Iranian UH uranium enrichment
Speaker 1: plant and happen to have this thumb drive, plug it
Speaker 1: into a computer system and infected it that way. That's
Speaker 1: just one potential way that scenario could have unfolded. But yeah,
Speaker 1: I mean, these things have have become ubiquitous in all
Speaker 1: areas of computing, so why not make a hard drive
Speaker 1: out of the same sort of approach, Because it means
Speaker 1: that you're using instead of a mechanical system, you're using
Speaker 1: an integrated circuit in order to store information. You no
Speaker 1: longer have to worry about spinning platters or reading heads
Speaker 1: or anything like that you can really decrease the amount
Speaker 1: of time that that latency time, so that when you
Speaker 1: are pulling information from the hard drive, it's much close
Speaker 1: sirt to the speeds that you would see on the
Speaker 1: CPU die itself, or at least in the computer's memory
Speaker 1: as opposed to on a traditional hard drive. And before
Speaker 1: we get too far into this, I do want to
Speaker 1: say something about what some of the sources of information
Speaker 1: we pulled from. We do have a great article on
Speaker 1: how stuff works about how flash drives work, and a
Speaker 1: lot of the information applies to solid state drives. Yeah
Speaker 1: they're they're not exactly the same, but yeah, they're they're
Speaker 1: kind of principles, are there. Yeah, they're close cousins, because
Speaker 1: a lot of the things that go into what make
Speaker 1: flash drives work apply to solid state drives. But an
Speaker 1: excellent resource on the web is an Ours Technica series,
Speaker 1: one of which one of the articles in that series
Speaker 1: is called solid State Revolution in Depth on how s
Speaker 1: s d s Really work by Lee Hutchinson. And I
Speaker 1: can't say enough good things about this article. It really
Speaker 1: is a comprehensive approach to how solid state drives work.
Speaker 1: End there's a little, uh, little latitude in the article,
Speaker 1: so it makes it it's not it's not dry reading. No, well,
Speaker 1: our our technical is like that. UM. It's also just
Speaker 1: just as a note, it's also very technical in spots too,
Speaker 1: So if you know, it's it's a they that site.
Speaker 1: It takes a little bit different approach to technology than
Speaker 1: than we do in a good way. It's at a
Speaker 1: different level. So it's it's it's definitely more serious if
Speaker 1: you if you're already familiar. Yeah, if you're already familiar
Speaker 1: with UM, with computer architecture and data and that sort
Speaker 1: of thing. Uh, it's an excellent resource. Otherwise, it may
Speaker 1: it may feel a little advanced for someone who is
Speaker 1: just curious about this but doesn't have any real background. However,
Speaker 1: it's well worthy read. So getting back to solid state drives, So,
Speaker 1: the idea of creating a solid state drive, uh was
Speaker 1: really really attractive because of that decreased latency. UM. There
Speaker 1: were some challenges, of course, because solid state drives they
Speaker 1: do not store information magnetically the way traditional hard drives do. No. Now,
Speaker 1: actually it sort of reminds me of electronic ink in
Speaker 1: a way. Interesting. Well, if you know something about electronic ink,
Speaker 1: you know that the capsules white or black generally are
Speaker 1: stored in between a sandwich of h material that holds
Speaker 1: a positive or negative charge, and that's how it reads
Speaker 1: a page. But once the page is there, it stays there.
Speaker 1: I see. So you're thinking of that as for it.
Speaker 1: Let's just say, for example, that the black parts of
Speaker 1: the screen are ones and the white parts are zeros,
Speaker 1: and they retain that even when the power is off,
Speaker 1: so they're non volatile. Right. That means that when you
Speaker 1: remove the power source from this system, it keeps that information. Now,
Speaker 1: that of course is extremely important when it comes to
Speaker 1: computers because, like Chris was saying, RAM is volatile memory.
Speaker 1: If you lose that power, then that information goes away.
Speaker 1: There's no longer a charge to maintain the information that
Speaker 1: stored in your computer's memory. You don't want that to
Speaker 1: happen to your hard drive because that means that every
Speaker 1: time you would turn off your computer or lose power,
Speaker 1: you would lose all the data stored there. You have
Speaker 1: to have non volatile memory to keep storage a possibility.
Speaker 1: Well nice, yeah, because I mean the old, the old, old,
Speaker 1: old computers that that Chris and I worked on didn't
Speaker 1: have hard drives. You had to store things on magnetic discs.
Speaker 1: H If you turned your computer on, it just went
Speaker 1: to its initial state. The only thing that was stored
Speaker 1: on there was the operating system because it was written
Speaker 1: in read only memory, which was non volatile, but it
Speaker 1: was also unchangeable. You couldn't write to it. So that
Speaker 1: meant that, you know, if you want to write a program,
Speaker 1: you had to store it on a disk, because if
Speaker 1: you tried to write it just on your computer, you
Speaker 1: didn't have a disk in there, and you turned the
Speaker 1: computer off, all your work has gone. This is also
Speaker 1: why if you've ever worked on a computer, and you've
Speaker 1: ever heard anyone say save your work, often that's why
Speaker 1: when you save your work, it's being saved to your
Speaker 1: hard drive, not to your computer's memory. So if you're
Speaker 1: working on something and you haven't saved it in a while,
Speaker 1: it may only exist in your computer's memory. If power
Speaker 1: goes out, you may lose all that work. As I
Speaker 1: have done on multiple occasions. I was actually in my
Speaker 1: college's computer lab during a storm and the screams out.
Speaker 1: There's nothing like working in any sort of computer environment
Speaker 1: when the power goes out and then you hear there's
Speaker 1: there's usually about a second and a half delay between
Speaker 1: the power going out and every single person making essentially
Speaker 1: the same noise, which sounds like this. Ah, I leaned
Speaker 1: back as I did that, so there was a little
Speaker 1: Doppler effect. But anyway, so yeah, this, this sort of
Speaker 1: of non volatile memory means that that information is going
Speaker 1: to stay there even when you turn the power off.
Speaker 1: This is the exact same sort of stuff we find
Speaker 1: in our MP three players and other mobile devices that
Speaker 1: because again, if we didn't have that, then every time
Speaker 1: you turned off your MP three player you would lose
Speaker 1: your entire library of songs. You have to reload it
Speaker 1: the next time you turn it on, right, right, Well,
Speaker 1: there is um to to complete my analogy. Yes, along
Speaker 1: with the electronic ink thing, the flash memory also uses cells. Um.
Speaker 1: It stores information in in cells, and that cell is
Speaker 1: either a one or a zero. Right to think of
Speaker 1: the cells like a sheet of grid paper. Yes, and
Speaker 1: you've got rows and you've got columns. Right, So the
Speaker 1: rows of cells. If you took one row of cells,
Speaker 1: we would call that in in solid state drive terminology,
Speaker 1: that would be a page. So one row of the
Speaker 1: cells would be a page, and then you would have
Speaker 1: several rows of cells and several columns of cells that
Speaker 1: would form what is called a block. And this is
Speaker 1: really important because it comes down to the way information
Speaker 1: is written and erased. In solid state drives. It turns
Speaker 1: out that you cannot individually change the cells within that
Speaker 1: grid paper. For example, if you if you had a
Speaker 1: sheet of grid paper in front of you, you could
Speaker 1: write a one or a zero and every single grid
Speaker 1: and if you wanted to, if you're writing in pencil,
Speaker 1: you could erase a single cell and change that one
Speaker 1: to a zero or zero to a one. You cannot
Speaker 1: do that with a solid state drive. We'll get into
Speaker 1: that in a little bit, but that's an important thing
Speaker 1: to think about from the start. Well, if you know
Speaker 1: something about hard drives, the the magnetic platter hard drives
Speaker 1: um when you when your computer, and that pretty much
Speaker 1: goes for all modern operating systems. Let's say you have
Speaker 1: a document and you realize that, well, you worked on
Speaker 1: it three years ago, You've turned it in. You know,
Speaker 1: I don't need to save it for anything, So I'm
Speaker 1: going to delete it, and I'm gonna tell my computer
Speaker 1: delete all that. First of all, the computer doesn't delete
Speaker 1: it deleted if you just tell it to, you know,
Speaker 1: throw it in the trash can, empty the trash can
Speaker 1: or recycle bin or whatever. It's actually still there on
Speaker 1: your hard drive, but it's been marked for deletion. So basically,
Speaker 1: when uh something else, Hey, I've created a new document
Speaker 1: and the computer goes, where can I say, ah, this
Speaker 1: is marked for deletion. I'll write over that old one. Um.
Speaker 1: That's one thing to note is that it can do that.
Speaker 1: That's the way that that computers work with magnetic platter
Speaker 1: hard drives. Now it also can do something else. Let's
Speaker 1: say you have five different documents and you've deleted these
Speaker 1: five documents. Well, those gaps are different sizes, but you're
Speaker 1: storing a brand new file and it's larger than all
Speaker 1: five of those. It can fill in sections, sort of
Speaker 1: like packets when you send when you break up an
Speaker 1: email file into a bunch of packets and they go
Speaker 1: and they reassemble themselves on the other side on somebody
Speaker 1: else's computer. These different gaps can be used to or
Speaker 1: parts of this file, which the computer will then reassemble
Speaker 1: as you need it. Um, that's when you need to
Speaker 1: fragment your hard drive. You know, they have uh sections
Speaker 1: and they're all scattered out. You've got applications, and then
Speaker 1: they're all in different places, in different sectors on different
Speaker 1: platters um, and they say, okay, I'm going to reorganize everything.
Speaker 1: And so the computer basically uses storage empty storage to
Speaker 1: reshuffle everything and put it back into sectors where all
Speaker 1: the parts of the filer together. And that makes a
Speaker 1: computer run a little bit faster when it's accessing those
Speaker 1: files because they're on one place and they don't have
Speaker 1: to reassemble them. Now, you can't do that with uh,
Speaker 1: solid state drives yea. In fact, when it gets down
Speaker 1: to a racing data off a solid state drive, it's
Speaker 1: pretty pretty complex. But before we get into that, let's
Speaker 1: talk a little bit, a little a little bit more
Speaker 1: about the way information is stored within these cells, so
Speaker 1: these grids on your grid paper. Yeah, I just thought
Speaker 1: it would be interesting to compare that to a platter
Speaker 1: drive entirely. Yeah, And it is important to make the
Speaker 1: comparisons between the two because there are advantages and disadvantages
Speaker 1: to both. That whole erasing thing or overwriting. You can't
Speaker 1: overwrite in an SSD, you can't erase stuff, but it
Speaker 1: takes a lot of effort actually um. But anyway, so
Speaker 1: in order to make the the cell have a value
Speaker 1: in it, you have to apply a voltage to that cell. Yes,
Speaker 1: I couldn't. I couldn't read that article without thinking of
Speaker 1: a C D C, the band with the dirty deeds.
Speaker 1: That they're cheap voltage. It uses high voltage. Actually that's important. Yes, yeah,
Speaker 1: in fact they're well uses both high and low voltage.
Speaker 1: There are two different ways of wiring these transistors together.
Speaker 1: That's what each of the cells actually represents. UM. There
Speaker 1: is the nor approach, which is a little simpler but
Speaker 1: less useful. Really, it's typical of flash drives, however, these
Speaker 1: smaller drives. So think of think of those those rows
Speaker 1: there and the uh the columns as having a a
Speaker 1: a circuit line going through each one. A right, So
Speaker 1: there are rows of circuits and columns of circuits, uh connections,
Speaker 1: really electronic connections, I should say, not just circuits, but
Speaker 1: electronic connections. So the rows would be word lines, the
Speaker 1: columns would be bit lines. So you would have this
Speaker 1: grid of word lines and bit lines sort of it
Speaker 1: would look kind of like a city block, like if
Speaker 1: you were looking for a city landscape, if you were
Speaker 1: looking at it from the air. So you have these
Speaker 1: these streets that are criss crossing um and you would
Speaker 1: kind of tell each cell what its contents were based
Speaker 1: upon applying voltages across these lines. I'm not gonna get
Speaker 1: too far into this because it really gets kind of
Speaker 1: complex and also involves a concept called quantum tunneling, which
Speaker 1: we have talked about here on tech stuff before, but
Speaker 1: it makes my brain hurt because it's Quantum tunneling is
Speaker 1: one of those things that is crazy to me. Tunneling
Speaker 1: is this concept that and it's it's a real thing,
Speaker 1: otherwise our electronics wouldn't work. Tunneling is this concept where
Speaker 1: you have a barrier, let's say, and you've got an
Speaker 1: electron that part of me an electron that's on one
Speaker 1: side of that barrier. With the right kind of energy,
Speaker 1: that electron can pass from one side of the barrier
Speaker 1: to the other side of the barrier as if it
Speaker 1: has tunneled through without actually physically tunneling through. And this
Speaker 1: all has to do with the potential for the electron
Speaker 1: to be in one position versus another. Uh, there's sort
Speaker 1: of you can think of it as a there's a
Speaker 1: radius around an electron that represents all the different locations
Speaker 1: that electron could be in. UH. If that electrons at
Speaker 1: the proper energy state, and there is barrier next to
Speaker 1: the electron, that radius might extend beyond the other side
Speaker 1: of that barrier. That means that there's the potential for
Speaker 1: that electron to be on the other side of that barrier,
Speaker 1: which means if there is a potential for it, sometimes
Speaker 1: the electron is on the other side of that barrier,
Speaker 1: as if the barrier weren't there. This drives me insane.
Speaker 1: It's like saying, if I'm if I'm running fast enough,
Speaker 1: there's a chance I'm going to be on the other
Speaker 1: side of the wall, not on this side of the wall.
Speaker 1: But every time I try that, I end up with
Speaker 1: the bloody knows I'm not quantum enough, is what it's. Yeah, anyway,
Speaker 1: so that that applies both to the NOR and the
Speaker 1: nand but the NOR version is the simplest one. You've
Speaker 1: got the bit lines and the word lines in this
Speaker 1: sort of criss cross pattern, and then and one. The
Speaker 1: bitlines are actually kind of um daisy chained in a
Speaker 1: way from one cell down to the next, And this
Speaker 1: becomes important when you were actually reading from the memory
Speaker 1: in order to determine what bit is in each cell
Speaker 1: UH And the way that works is that you apply
Speaker 1: a weak voltage across these lines to try and determine
Speaker 1: if a full circuit is being made, and if there
Speaker 1: you get two different outcomes depending on if there's a
Speaker 1: one or a zero. Right, So if you get one outcome,
Speaker 1: for example, if the circuit is made, you know that
Speaker 1: the value is uh. You know what the value is
Speaker 1: inside that cell because it can only be that value,
Speaker 1: and if the circuit is not made, then you know
Speaker 1: it's the opposite value, right, And so you're you're thinking, well,
Speaker 1: if the charge goes through, it means this. If the
Speaker 1: charge doesn't go through, it means that you collect that
Speaker 1: with all of these cells, and that's what builds up data. Remember,
Speaker 1: each of these cells represents one bit, so a zero
Speaker 1: or a one, unless that's a well, I guess I
Speaker 1: should say that that would be an s l C,
Speaker 1: a single level cell which can represent either a zero
Speaker 1: or a one. You could also have a multi level cell,
Speaker 1: and in fact, most ssd s are multi level cells. Now,
Speaker 1: these can contain uh two or more bits. Usually it's
Speaker 1: two bits or three bits, which means that if it's
Speaker 1: a two bit system, there are four potential values that
Speaker 1: you could find within that cell. It would either be zero, zero, zero, one,
Speaker 1: one zero, or one one. But with a multi level cell, UH,
Speaker 1: it's a little more complicated as well, because you know,
Speaker 1: like I said, you could use the weak voltage to
Speaker 1: determine whether or not the content of a single layer
Speaker 1: cell is a zero or a one. With multi level
Speaker 1: level cell, because there are four potential UH outcomes, you
Speaker 1: have to use different voltages and essentially you work from
Speaker 1: the weakest and you work your way up and as
Speaker 1: soon as that circuit is complete, then you know what
Speaker 1: the value of that cell is. Did I just Chris's
Speaker 1: brains are actually leaking out of his ears right now.
Speaker 1: I just find the whole thing revolting. Yeah, I thought
Speaker 1: you get a charge out of it. So anyway, Yeah,
Speaker 1: it all has to do with these voltages and UH
Speaker 1: and that that's all the reading information to write to
Speaker 1: UH to It is UM even more complex actually. Well.
Speaker 1: One of the things to note though is that making
Speaker 1: these changes UH the voltage changes can be dangerous UM
Speaker 1: using the high voltage to to do these changes, which
Speaker 1: is one of the reasons why it is so difficult
Speaker 1: to uh to erase and rewrite on this flash memory
Speaker 1: that that's used in SSCs. That's one of the reasons.
Speaker 1: The other reason is that when you are writing information
Speaker 1: to a an SSD, you have to write it in
Speaker 1: in pages so roads. So think of think of this
Speaker 1: grid paper again. You can only write to a single
Speaker 1: row at a time, all right, when you're erasing, you
Speaker 1: have to erase these in blocks of pages. You can't
Speaker 1: erase one row, you can't erase one page. You have
Speaker 1: to erase a block of pages, which tends to be
Speaker 1: about a D twenty eight rows total, which equals about
Speaker 1: five twelve kilobytes. Uh. There's actually some extra information there too,
Speaker 1: because there are a few, uh few cells that are
Speaker 1: dedicated to things like error correction and other information. So
Speaker 1: there's technically a little more than that. But the data
Speaker 1: that you're actually writing to the SSD or erasing from
Speaker 1: the SSD is either in four or eight kilobyte pages. Again,
Speaker 1: that depends upon the format of the solid state drive.
Speaker 1: And uh, when you're racing's aud twenty eight pages, so
Speaker 1: five twelve kilobites so or for the four kilobyte pages anyway,
Speaker 1: so you've got you can write in a page, you
Speaker 1: erase in a block. This is why it's really hard
Speaker 1: to you can't. This is why you can overwrite information
Speaker 1: because your file that you know that this has nothing
Speaker 1: to do with file size. This is just the individual
Speaker 1: bits that are found within those cells. Right. So a
Speaker 1: block might contain the end of one file in the
Speaker 1: beginning of another file. So you can't erase an entire block, uh,
Speaker 1: just because you erased one particular file, because you if
Speaker 1: you did that, then you would lose the beginning of
Speaker 1: a of an unrelated file that you did not delete, right.
Speaker 1: And and it treats old files that have been marked
Speaker 1: for deletion as information that should be saved. It doesn't
Speaker 1: make Uh. There's on every drive there is a controller
Speaker 1: that provides instruction for the drive, and it doesn't know
Speaker 1: the difference between the file that I just uh quote
Speaker 1: unquote on my computer deleted and the computer marks for delete. Oh,
Speaker 1: it's okay to overwrite this sector of the drive, um
Speaker 1: versus a file that I want to keep. So it
Speaker 1: treats anything that's written in there as well. I better
Speaker 1: save this. Yeah, And just so that you guys can
Speaker 1: kind of envision what is going on here, So let's
Speaker 1: go back to that grid paper example. Let's say you've
Speaker 1: got a sheet of grid paper. If this were like
Speaker 1: a solid state drive, every single one of those cells,
Speaker 1: if this was a brand new sheet, nothing had been
Speaker 1: saved to the sheet yet, actually every single one of
Speaker 1: those cells would have a one in them. And when
Speaker 1: you were writing information, what you do is you apply
Speaker 1: a certain voltage and you would switch that one to
Speaker 1: a zero. Switch. Switching the one to a zero is
Speaker 1: not such a big deal. Switching the zero back to
Speaker 1: one is a huge deal. And here's here's why you
Speaker 1: cannot overwrite specific parts of this this page. You have
Speaker 1: to use enough voltage to switch that back to a
Speaker 1: one that if you were to try and target a
Speaker 1: single cell, that energy could overflow into neighboring cells, which
Speaker 1: would make those flip. And if you're making all of
Speaker 1: those flip, that means you've just corrupted the data, right
Speaker 1: because not all those not all of those zeros need
Speaker 1: to be turned back into ones. Effective students going yeah,
Speaker 1: so that's so, that's why you can't target a specific cell.
Speaker 1: You have to do it in these blocks. And uh,
Speaker 1: the way, the way a solid state drive actually does
Speaker 1: this handles this because eventually you will have to have
Speaker 1: that information race or else you'll run out of space.
Speaker 1: You're a space just even every time you save a
Speaker 1: new version of that document, if it's a document that
Speaker 1: you're working on, as opposed to like we'll use that
Speaker 1: as an example, UM as a type of file you're
Speaker 1: you're creating. Let's say that you've created a document. Every
Speaker 1: time you save a new version of it, it's writing
Speaker 1: that information to more pages on your solid state drive. Well,
Speaker 1: if you never array, if if it never had the
Speaker 1: opportunity to erase the information on that drive, you would
Speaker 1: run out of space eventually. Yes, So the way it
Speaker 1: tries to handle this is that eventually there's a there's
Speaker 1: got to be a connection between the operating system and
Speaker 1: the solid state drive that lets the solid state drive. No,
Speaker 1: this particular information that is stored within your pages is stale.
Speaker 1: This information does not really UM this this isn't pertinent anymore.
Speaker 1: You can get rid of this. What will happen is rubbish. Yeah,
Speaker 1: and there's this is called garbage collection. Actually, what happens
Speaker 1: is the solid state drive will take a block that
Speaker 1: contains the pages that have stale information, and we'll copy
Speaker 1: that entire block and save it again within the drive.
Speaker 1: So now you're saying, wait a minute. Now you've just uh, well,
Speaker 1: technically it only copy the stuff that is um that
Speaker 1: is not stale. So you've got a block of of pages.
Speaker 1: Some of those pages are stale, some of the pages
Speaker 1: aren't stale. The solid state drive will copy the stuff
Speaker 1: that's not stale and paste into a new block and
Speaker 1: a new series of pages. So you've just doubled all
Speaker 1: the non stale content that is on your solid state drive.
Speaker 1: And I hear you screaming, but you said this is
Speaker 1: to conserve space. How can you conserve space by copying
Speaker 1: and pasting? Here's how. After that information has been copied
Speaker 1: and pasted into the new section of the solid state drive,
Speaker 1: the old block that has both the stale and not
Speaker 1: stale information in it can be erased. You can apply
Speaker 1: that high voltage, flip those zeros back to ones, and
Speaker 1: you can do it safely because you've already duplicated the
Speaker 1: non stale data into new pages. The stale data does
Speaker 1: not get duplicated, so it gets erased, which means that
Speaker 1: that block is now available to write to again. There's
Speaker 1: another downside here, which is that every single time you're
Speaker 1: writing to those cells, you're actually breaking down the system
Speaker 1: a little bit. There's only so many times you can
Speaker 1: do this and the cells will remain viable. Eventually, the
Speaker 1: cells will no longer be able to hold a charge
Speaker 1: because they've been broken down too many times with this
Speaker 1: voltage being applied to them. Um SSD vendors have gone
Speaker 1: to some effort to prevent that from being an issue,
Speaker 1: at least for a while. Um In a lot of cases,
Speaker 1: there will be uhm extra space on the drive of
Speaker 1: which you are unaware. Right. You might have a say,
Speaker 1: let's say that you get I don't know, a sixty
Speaker 1: gigabit gigabyte rather um hard drive space and there's actually
Speaker 1: sixty eight gigabytes in there. You just don't know about
Speaker 1: this other eight because they've been included to take into
Speaker 1: account this issue. So that one uh this whole garbage
Speaker 1: collection process has some space to work in and you
Speaker 1: won't end up filling up your hard drive before it
Speaker 1: can take advantage of that and to as cells die
Speaker 1: and are unusable, it can open up new pages of
Speaker 1: cells that have not been written to an X number
Speaker 1: of times, and we're talking thousands of times here. It's
Speaker 1: not like, you know, it's not like you're gonna fill
Speaker 1: up your hard drive and three days later it's gonna
Speaker 1: be useless. But well, it shouldn't be. No, it shouldn't be.
Speaker 1: But but you know, your mileage may vary depending upon
Speaker 1: manufacturer and model. But the ideally it would take thousands
Speaker 1: and thousands and thousands of times before it would become obsolete,
Speaker 1: before it would not work anymore. And the thing is
Speaker 1: that most of us use our computers frequently enough where
Speaker 1: eventually that could happen. I mean, if you upgrade on
Speaker 1: a regular basis, you may never notice this problem. But
Speaker 1: if you don't, you might notice that your computer takes
Speaker 1: longer to pull information from the hard drive that it
Speaker 1: used to and you may notice that you are running
Speaker 1: out of hard drive space when you thought that you
Speaker 1: should really have more. Yeah, why has all that gone?
Speaker 1: And it's because those cells are no longer viable. Well, um,
Speaker 1: to prevent this, the controller on the s s D
Speaker 1: is designed to route traffic in a way that will
Speaker 1: try to put a fairly even uh distribution distribution of
Speaker 1: usage across the different cells on the drive UH, thus
Speaker 1: hopefully ensuring that no set of cells is worn down
Speaker 1: more than the others. They're trying to put put even
Speaker 1: wear and tear on it. Um. But the more full
Speaker 1: you get now they're One of the complaints about s
Speaker 1: s d s is that they seem to grow slower
Speaker 1: as time goes on. That's because that information, uh, those
Speaker 1: those cells are getting full of information, those pages are
Speaker 1: filling up. And because of the way they work UM
Speaker 1: and they have to write and rewrite blank pages at
Speaker 1: a time, Uh, it can seem to slow down because
Speaker 1: there isn't as much space to UM for them to
Speaker 1: the controller to route the information, re and and regroup
Speaker 1: things into pages uh fresh pages that can be written
Speaker 1: and rewritten or not rewritten but UM erased and written
Speaker 1: to UM. So UM. You know that that's that's sort
Speaker 1: of a I would say an illusion. It's not really
Speaker 1: an illusion. But that's why it's not because the drive
Speaker 1: is uh crapping out generally, I mean, uh yeah, I
Speaker 1: mean the vendors for these devices generally say that they're
Speaker 1: good for you know, tens of thousands of read write cycles,
Speaker 1: so they should be good for for years. Of course,
Speaker 1: that doesn't mean you shouldn't back up your hard drive. However,
Speaker 1: it does mean that defragging like we used to do
Speaker 1: with the magnetic traditional platter drives is not a good
Speaker 1: idea because you're adding to writing and rewriting uh those cells. Right,
Speaker 1: You're you're effectively you are decreasing the life span of
Speaker 1: your hard drive. And the controller really should be doing
Speaker 1: that anyway with a garbage collection and um organization of
Speaker 1: that that work, so it should be less of an
Speaker 1: issue than it used to be. And the controller really
Speaker 1: is kind of like a very small, very specialized computer.
Speaker 1: So in a way, you have a computer within your
Speaker 1: computer because the controller is is taking this information and
Speaker 1: putting it in the most uh, the the optimized format
Speaker 1: and layout. So yeah, it's uh, it's an interesting approach
Speaker 1: using this voltage difference instead of magnetism in order to
Speaker 1: store information, and it has become incredibly useful, especially for
Speaker 1: things like portable electronics. I mean, it's really decreased the
Speaker 1: size of what our electronics can be. Plus you can
Speaker 1: go running with it and not worry about crashing the
Speaker 1: platters on your hard drive. Ye. This is why back
Speaker 1: when I remember when m P three's were MP three
Speaker 1: players were first coming out, and there was always the
Speaker 1: argument of do you get the one with the spinning
Speaker 1: hard drive, or do you get the one with the
Speaker 1: flash hard drive? And the flash hard drives tended to
Speaker 1: be more expensive, but they also were the ones you
Speaker 1: could go and exercise with and not worry about them,
Speaker 1: you know, something skipping around or or or corrupting a
Speaker 1: file or crashing? UM, do you would would you like
Speaker 1: to wrap up? Or should we mention encryption? We could mention, well,
Speaker 1: you can mention encryption because frankly, my my research did
Speaker 1: not cover that topic. UM okay, well the uh UM.
Speaker 1: This is another in the series of articles UM on
Speaker 1: ours Technical about S s d S, also written by
Speaker 1: Lee Hutchinson UM. And it's kind of fascinating because uh
Speaker 1: and in the process of UM compression UM, they go
Speaker 1: through a D duplication phase. So it's sort of you know,
Speaker 1: if they find two copies of the same information, it
Speaker 1: will essentially get rid of one so that it takes
Speaker 1: up less space and the hard drive. That's essentially how
Speaker 1: how these things are done. And it's done in UM
Speaker 1: other types of files to UM image and sound and uh,
Speaker 1: you know those kinds of things that they find the
Speaker 1: same information, they can reduce the amount of information in
Speaker 1: that file. Well, they do that with hard drives too.
Speaker 1: But one of the interesting things that that Hutchinson mentions
Speaker 1: is now that modern operating systems are allowing you to
Speaker 1: encrypt your entire hard drive. That actually makes it tougher
Speaker 1: for s s d s because they can't de duplicate
Speaker 1: that information anymore. Because once you encrypted a file, it
Speaker 1: has its own individual signature. So even if they were
Speaker 1: the same exact document, um, the computer sees it as
Speaker 1: two different encrypted documents because the encryption information is slightly different,
Speaker 1: so will no longer recognize them as the same information.
Speaker 1: So they will see them as completely different information. Taking
Speaker 1: bulky and safe exactly. So it takes up the same file,
Speaker 1: will take up twice as much space if it's been duplicated,
Speaker 1: and it will not be the leaded because there's just
Speaker 1: enough difference there so that it has essentially fooled the
Speaker 1: controller into thinking it's two files, not one that's been
Speaker 1: duplicated to two files. And what now? Um. The other thing, uh,
Speaker 1: the thing to know is, you know, these these devices
Speaker 1: are coming down in cost um. They're showing up more
Speaker 1: often in uh, in laptops, ultra books and and you know,
Speaker 1: just a few years ago, I remember that it was
Speaker 1: really unusual to find a solid state drive in a computer,
Speaker 1: and you were paying a premium for that if you
Speaker 1: wanted it. And it was kind of interesting because at
Speaker 1: the time, the solid state drives, while you were paying
Speaker 1: a premium, tended to have a smaller capacity than the
Speaker 1: traditional hard drives did when they first started coming out. Well,
Speaker 1: now we've seen that slowly start to change, and that's
Speaker 1: to be expected. That's the way technology tends to work
Speaker 1: in the market. We tend to see when it first
Speaker 1: comes out, it tends to be pretty expensive and fairly limited,
Speaker 1: and as it advances and we get better at the
Speaker 1: production approach, these prices start to fall. And then next
Speaker 1: thing you know, it's everywhere. Yes, so um, you know
Speaker 1: it seems like they're they're becoming more common. Um. You know,
Speaker 1: even even in run of the mill laptops. However, UM,
Speaker 1: you know, the cost is still not as as inexpensive
Speaker 1: as traditional hard drives. UM. And you know, you do
Speaker 1: have those trade offs to be made versus the traditional
Speaker 1: So if you were getting say you really wanted a
Speaker 1: nice workstation to to use at home, you already have
Speaker 1: a laptop, um, and you were choosing whether you wanted
Speaker 1: to spend that extra hundred dollars two hundred dollars for
Speaker 1: an SSD. You know it does. You would get some
Speaker 1: uh savings in in uh A cost if you went
Speaker 1: with the magnetic drive. UM, but you would trade off
Speaker 1: speed for that and the number of read write cycles.
Speaker 1: Of course, magnetic drives have their own idiosyncrasies and you
Speaker 1: may or may not lose your your hard drive. No,
Speaker 1: it's not not to say that that the older hard
Speaker 1: drives are any better. They just have a different set
Speaker 1: of pros and cons. Yeah, exactly. So, yeah, it all
Speaker 1: depends on what your use case scenario is. And I mean, like,
Speaker 1: i have machines at home that of both types. So
Speaker 1: I've got machines that have a spinning hard drive, I
Speaker 1: gout machines that have solid state drives. I have an
Speaker 1: external drive that's a solid state drive that I used
Speaker 1: for backups. Uh. You know, there's a lot of different
Speaker 1: ways of going about this, and I think that both
Speaker 1: approaches have their own advantages and disadvantages that will apply
Speaker 1: to you based upon the way you use your machines.
Speaker 1: So that's always a good thing to think about. UH.
Speaker 1: And it may even be that to you. It doesn't
Speaker 1: really matter other than maybe the fact that you can
Speaker 1: get a solid state drive with a small reform factor
Speaker 1: than you could if it were a physical hard drive,
Speaker 1: you know, the mechanical hard drive. I should say mechanical,
Speaker 1: not physical, because they're both physical. It's not it's not
Speaker 1: a virtual hard drive. Um so yeah, I mean that's
Speaker 1: it's all up to the way you use your machines
Speaker 1: and what you what your personal preferences are, and I
Speaker 1: guess what your budget is as well. Um yeah, I'll
Speaker 1: never forget. I knew that solid state memory was going
Speaker 1: to be a big deal. This flash based memory sticks
Speaker 1: not solid state drives, slightly different, but I knew it
Speaker 1: was gonna be a big deal when we went to
Speaker 1: I guess is when I went to C E. S.
Speaker 1: It was the year after the two of us went
Speaker 1: because the year that Chris and I both went to
Speaker 1: see EES, we picked up lots and lots of press
Speaker 1: kits that were either paper press kits or CD comic
Speaker 1: disk space. And then the next year I started seeing
Speaker 1: companies produce their press kits on USB thumb drives, and
Speaker 1: that's when I was I thought, Okay, this is a
Speaker 1: big enough deal, because now it's cheap enough where these
Speaker 1: companies can produce thousands of these things for an exhibition.
Speaker 1: Because you've got lots and lots of people at c S,
Speaker 1: you have to produce tons and tons of these not
Speaker 1: literally tons and tons, but lots and lots of these
Speaker 1: thumb drives, uh, in order to give them out to
Speaker 1: all the people who stop by. Of course, nowadays they
Speaker 1: don't even do that anymore. Now you get a card
Speaker 1: that has a U R L and you go to
Speaker 1: a website that has the press release, which is even
Speaker 1: better really, although it does mean that I don't end
Speaker 1: up with lots of thumb drives that I can use
Speaker 1: once I erase the that's on there. You mean you
Speaker 1: haven't moved everything into the cloud. Now I'm working on it,
Speaker 1: but you know there. Here's the other thing about the
Speaker 1: cloud that's a totally different discussions. I'm gonna I'm gonna
Speaker 1: drop this. I was about to go off on a
Speaker 1: cloud rant about how all my information is in different
Speaker 1: pockets in the cloud. That's my problem. Now, so let's
Speaker 1: let's that's a totally different podcast, which I'm sure we'll do.
Speaker 1: And we've talked about cloud storage in the past anyway,
Speaker 1: So we're gonna wrap this up. Guys, I do recommend
Speaker 1: you go to ours Technica and look at those articles
Speaker 1: if you are interested in solid state drives and what
Speaker 1: makes them more work. We also have the flash based
Speaker 1: memory article on how stuff works that has h illustrations
Speaker 1: and animations in it to help explain the process. There
Speaker 1: are a lot of great resources on the web to
Speaker 1: really explain this stuff in further details, so if you're interested,
Speaker 1: I highly recommend you seek them out because it's a
Speaker 1: fascinating subject and I wish we could go into even
Speaker 1: more detail, but one an audio format podcast makes it
Speaker 1: difficult to do that. And to frankly, my understanding of
Speaker 1: the subject matter is only so deep, right, I mean,
Speaker 1: I think there comes a point where I've hit my
Speaker 1: threshold and I'm thinking, all right, I kind of get this,
Speaker 1: but I need more time to really digest it. So uh, Fortunately,
Speaker 1: I'm sure you guys have nothing but time on your hands.
Speaker 1: I mean, you're listening to us, right, So go out
Speaker 1: there and check it out. And uh, if you want
Speaker 1: to send us any suggestions for topics, or you have
Speaker 1: a question, or you just want to say howdy, you
Speaker 1: can write us our email addresses text uff at Discovery
Speaker 1: dot com, or send us a message on Twitter or Facebook.
Speaker 1: Our handle at both those locations is text of hs
Speaker 1: W and Chris and I will talk to you again
Speaker 1: really soon. For more on this and thousands of other topics,
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