From the course: CompTIA A+ (220-1001) Cert Prep 2: Microprocessing and RAM
RAM technologies
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- If you're going to be having a computer, - If you're going to be having a computer, you're going to be having some RAM in it you're going to be having some RAM in it so in this episode what I want to talk about so in this episode what I want to talk about are the different types of RAM technologies are the different types of RAM technologies that have been out over the years, that have been out over the years, because I want you to be able because I want you to be able when you're buying a new motherboard, or picking a system, when you're buying a new motherboard, or picking a system, to be able to get the kind of RAM to be able to get the kind of RAM you need for your computer. you need for your computer. So let's take a look, what I've got here in front of me So let's take a look, what I've got here in front of me is a bunch of RAM technologies that span a number of years, is a bunch of RAM technologies that span a number of years, and what I'd like to concentrate on and what I'd like to concentrate on is this stick of RAM right here, is this stick of RAM right here, this is, as far as I'm concerned, the original RAM. this is, as far as I'm concerned, the original RAM. This is known as synchronous data RAM, or SDRAM, This is known as synchronous data RAM, or SDRAM, there was RAM before this but it was there was RAM before this but it was the RAM of your forefathers the RAM of your forefathers and I don't want to talk about it, it's not on the exam, and I don't want to talk about it, it's not on the exam, and if you find a computer that still uses that ancient RAM, and if you find a computer that still uses that ancient RAM, well, it's probably going to be in a museum, so. well, it's probably going to be in a museum, so. Anyway, SDRAM is interesting because in other episodes Anyway, SDRAM is interesting because in other episodes we talk about the system crystal that we talk about the system crystal that sets the metronome for the CPU, sets the metronome for the CPU, well synchronous means that it's synchronized well synchronous means that it's synchronized to the same crystal and that's very, very helpful to the same crystal and that's very, very helpful because any given click of the clock because any given click of the clock we can count on this stick of RAM to do something for us. we can count on this stick of RAM to do something for us. So SDRAM was the first one out of the box, So SDRAM was the first one out of the box, now what's important for me is that now what's important for me is that as you look at the stick of RAM as you look at the stick of RAM there's a couple of things that I want you to notice, there's a couple of things that I want you to notice, number one this is 168 pins, number one this is 168 pins, go ahead and count 'em real quick, oh I'm kidding, go ahead and count 'em real quick, oh I'm kidding, but what is very important is you'll notice but what is very important is you'll notice that there are two notches. that there are two notches. SDRAM sticks are the only type of RAM out there SDRAM sticks are the only type of RAM out there that have two notches that you're going to run into any more. that have two notches that you're going to run into any more. Now SDRAM runs fantastically well, Now SDRAM runs fantastically well, but just like your CPU has a speed, your SDRAM has a speed. but just like your CPU has a speed, your SDRAM has a speed. So when we talk about SDRAM, So when we talk about SDRAM, we talk about the speeds associated with it, we talk about the speeds associated with it, so with SDRAM it was just running so with SDRAM it was just running at whatever your motherboard speed was. at whatever your motherboard speed was. 66 megahertz, 100 megahertz, whatever it was, 66 megahertz, 100 megahertz, whatever it was, that was just the speed associated with it. that was just the speed associated with it. We're going to see that; that gets a little bit We're going to see that; that gets a little bit more complicated as the technologies improve. more complicated as the technologies improve. So the first big leap forward from SDRAM So the first big leap forward from SDRAM is this stick right here. is this stick right here. This stick is known as Double Data Rate, or DDR SDRAM, This stick is known as Double Data Rate, or DDR SDRAM, but most of us'll just say DDR RAM. but most of us'll just say DDR RAM. DDR RAM, Double Data Rate is the clue, DDR RAM, Double Data Rate is the clue, basically for any one given click of the clock, basically for any one given click of the clock, this would give us two bits of information this would give us two bits of information which was a huge breakthrough and really sped RAM up a lot. which was a huge breakthrough and really sped RAM up a lot. Now the problem we're going to run into now Now the problem we're going to run into now is how do we define that speed? is how do we define that speed? Because when you're going to buy RAM Because when you're going to buy RAM your motherboard needs RAM at a certain speed, your motherboard needs RAM at a certain speed, it's in the motherboard book, it's in the motherboard book, so when you go to the store to buy your RAM so when you go to the store to buy your RAM you need to make sure that you have those speeds you need to make sure that you have those speeds and that's where we come into the DDR, or PC ratings. and that's where we come into the DDR, or PC ratings. Let me give you an example of this for DDR. Let me give you an example of this for DDR. Here's some examples of DDR speeds that we used to see. Here's some examples of DDR speeds that we used to see. So you'll notice on the left we have a clock speed, So you'll notice on the left we have a clock speed, and this is basically the speed of the motherboard itself. and this is basically the speed of the motherboard itself. The speed ratings, or the DDR Speed Ratings, The speed ratings, or the DDR Speed Ratings, are known as, it'll say DDR then a dash and them some speed. are known as, it'll say DDR then a dash and them some speed. Now if you look closely here it's pretty straightforward, Now if you look closely here it's pretty straightforward, all you have to do is double it. all you have to do is double it. It's Double Data Rate, that makes sense. It's Double Data Rate, that makes sense. Now the next thing I want you Now the next thing I want you to look at is the PC Speed Rating. to look at is the PC Speed Rating. You can see either one of these, You can see either one of these, when you're buying RAM it's going to be when you're buying RAM it's going to be printed on the RAM stick, printed on the RAM stick, or at least in the box you get it in. or at least in the box you get it in. So this PC Speed Rating is simply measuring the same speed So this PC Speed Rating is simply measuring the same speed but instead of in bits, in bytes. but instead of in bits, in bytes. So just take the DDR rating, multiply it times eight, So just take the DDR rating, multiply it times eight, and you get the PC rating. and you get the PC rating. Pretty straightforward, right? Pretty straightforward, right? Fantastic. Fantastic. DDR was a huge breakthrough DDR was a huge breakthrough and it's really, really important to me and it's really, really important to me that you be comfortable with these DDR, that you be comfortable with these DDR, and these PC ratings, in fact, and these PC ratings, in fact, you're about to see a few more you're about to see a few more of these as we progress through. of these as we progress through. So time marches forward, So time marches forward, and let's go ahead and get our next generation, and let's go ahead and get our next generation, and that's right here, this is DDR2. and that's right here, this is DDR2. Now forget the metal cover, Now forget the metal cover, to me these metal covers, they're called heat spreaders, to me these metal covers, they're called heat spreaders, I think they're more sales than anything else, I think they're more sales than anything else, that's my opinion, but what is important, that's my opinion, but what is important, and you've got to look very, very carefully, and you've got to look very, very carefully, it's hard to catch this. it's hard to catch this. So if SDRAM used a 168 pin, DDR used 184 pins, So if SDRAM used a 168 pin, DDR used 184 pins, and notice there's only a single notch, and notice there's only a single notch, DDR2 uses a 240 pin, and it looks like the notches DDR2 uses a 240 pin, and it looks like the notches are in the same place, are in the same place, but if I put 'em right next to each other, but if I put 'em right next to each other, notice the subtle offset between those two notches. notice the subtle offset between those two notches. Be glad for that. Be glad for that. The idea is that one particular motherboard The idea is that one particular motherboard is going to use one particular technology of RAM, is going to use one particular technology of RAM, and they don't want you to accidentally and they don't want you to accidentally put DDR into a motherboard that needs DDR2, put DDR into a motherboard that needs DDR2, so we're glad that the notches are a little bit offset. so we're glad that the notches are a little bit offset. DDR2 really set the standard for RAM on systems, DDR2 really set the standard for RAM on systems, and it hand a long, long lifespan. and it hand a long, long lifespan. It also had some speed ratings, let's take a look at those. It also had some speed ratings, let's take a look at those. So here's a table of common DDR2 speeds, So here's a table of common DDR2 speeds, now keep in mind in all these tables, now keep in mind in all these tables, I don't list every possible speed, it would be 40 feet long, I don't list every possible speed, it would be 40 feet long, but these are the more common ones. but these are the more common ones. So once again we look at our core speed So once again we look at our core speed which I call the motherboard speed, which I call the motherboard speed, and you'll see that's the speed and you'll see that's the speed of the system crystal itself. of the system crystal itself. Now with DRR, it goes ahead and does the double, Now with DRR, it goes ahead and does the double, as I'd mentioned before, but with DDR2, as I'd mentioned before, but with DDR2, it actually doubles a second time it actually doubles a second time by using this interesting function by using this interesting function which you call a pre fetch, which you call a pre fetch, but the bottom line is DDR2 was really but the bottom line is DDR2 was really four times faster than regular SDRAM, four times faster than regular SDRAM, twice as fast as DDR. twice as fast as DDR. So if we take a look at this, first of all, So if we take a look at this, first of all, when you look at the speed ratings, when you look at the speed ratings, again these are printed on the boxes when you buy RAM, again these are printed on the boxes when you buy RAM, notice that DDR2, the actual DDR2 rating notice that DDR2, the actual DDR2 rating is going to say DDR2 on the box, is going to say DDR2 on the box, and on the box when we're talking about DDR2 and on the box when we're talking about DDR2 you'll see it says PC2 and then whatever speed, you'll see it says PC2 and then whatever speed, you go ahead, look at the third column, you go ahead, look at the third column, multiple it times eight and you get that PC rating, multiple it times eight and you get that PC rating, you always multiple times eight, you always multiple times eight, remember that, it's on the exam. remember that, it's on the exam. So what is important, if I'm holding two different So what is important, if I'm holding two different sticks of RAM and I don't have the notches memorized, sticks of RAM and I don't have the notches memorized, so I can't tell them apart, so I can't tell them apart, and the sticks don't say DDR or DDR2, and the sticks don't say DDR or DDR2, all I need to do is look at that PC rating. all I need to do is look at that PC rating. If the PC rating says just PC dash, If the PC rating says just PC dash, then we know that that's DDR. then we know that that's DDR. If it says PC2 and then a dash, then we know that it's DDR2. If it says PC2 and then a dash, then we know that it's DDR2. Just by looking at the speed rating, fantastic. Just by looking at the speed rating, fantastic. Let's go ahead and keep marching on. Let's go ahead and keep marching on. Now, what I've got right here is DD3. Now, what I've got right here is DD3. Yep, DDR3 one again doubled from DDR2, Yep, DDR3 one again doubled from DDR2, and created some wonderful bandwidths. and created some wonderful bandwidths. Now again, if we look at the sticks very, very carefully, Now again, if we look at the sticks very, very carefully, by the way DDR3 uses a 240 pin stick by the way DDR3 uses a 240 pin stick just like DDR2 does, but again, just like DDR2 does, but again, can we catch it on camera? can we catch it on camera? It should be more obvious this time. It should be more obvious this time. We can see that the slots are very much offset, We can see that the slots are very much offset, so you can't accidentally put it into the wrong motherboard. so you can't accidentally put it into the wrong motherboard. DDR3, it didn't have that long of a lifespan, DDR3, it didn't have that long of a lifespan, it was around for a while but it also it was around for a while but it also introduced some much faster speeds, introduced some much faster speeds, let's take a look at those. let's take a look at those. So at this point in the game So at this point in the game I'm hoping you're kind of used to looking at the table, I'm hoping you're kind of used to looking at the table, so on the left once again is our core speed, so on the left once again is our core speed, notice that the core speeds keep getting faster and faster, notice that the core speeds keep getting faster and faster, technology marches on, motherboards are getting faster. technology marches on, motherboards are getting faster. So the actual DDR I/O Speed is going to be four times that, So the actual DDR I/O Speed is going to be four times that, in this case, so it's actually doubling in this case, so it's actually doubling once again what we had from DDR2 once again what we had from DDR2 so our speed ratings, now look this is very important, so our speed ratings, now look this is very important, you see it says DDR3? you see it says DDR3? See it says PC3? See it says PC3? That's how you know the speed rating That's how you know the speed rating defines the actual technology of RAM. defines the actual technology of RAM. Just because it says PC3, just because it says DDR3, Just because it says PC3, just because it says DDR3, we instantly know that we're talking about DDR3 memory we instantly know that we're talking about DDR3 memory and all you have to do once again, and all you have to do once again, let's take a look where it says DDR3-800, let's take a look where it says DDR3-800, multiply it times eight and you get multiply it times eight and you get the actual PC3 Speed Rating. the actual PC3 Speed Rating. People will say to me, Mike, People will say to me, Mike, why is these two different speed ratings so important? why is these two different speed ratings so important? Well the answer's pretty simple, Well the answer's pretty simple, because different RAM makers will use one or the other, because different RAM makers will use one or the other, a lot of them are using both when you actually a lot of them are using both when you actually look on the box itself but I can't guarantee it, look on the box itself but I can't guarantee it, and I want you to be able to walk in to your computer store and I want you to be able to walk in to your computer store and order the right stuff for your system. and order the right stuff for your system. The motherboard book itself is going to use these The motherboard book itself is going to use these to tell you what kind of RAM you need, to tell you what kind of RAM you need, so be comfortable with this terminology. so be comfortable with this terminology. The last type of general purpose RAM The last type of general purpose RAM I want to talk about is DDR4, and I've got a stick right here. I want to talk about is DDR4, and I've got a stick right here. Now DDR4 uses a 288 pin stick, Now DDR4 uses a 288 pin stick, and again, this one you can see it's well offset and again, this one you can see it's well offset from anybody else, there's no question mark from anybody else, there's no question mark that there's are different types of technology. that there's are different types of technology. DDR4 is the fastest RAM that's described DDR4 is the fastest RAM that's described on the Comptia A+ exam and right now on the Comptia A+ exam and right now it's by far the most common, it's by far the most common, and it's probably going to be around for a while. and it's probably going to be around for a while. DDR4 has some outrageous speeds, let me show you those. DDR4 has some outrageous speeds, let me show you those. As we take a look at the speeds here with DDR4, As we take a look at the speeds here with DDR4, first of all, if you look on the left hand side first of all, if you look on the left hand side these are the motherboard speeds, they're getting faster. these are the motherboard speeds, they're getting faster. But this time as opposed to the other tables But this time as opposed to the other tables we tend to use the term bandwidth we tend to use the term bandwidth when we're talking about DDR4. when we're talking about DDR4. So what we're talking about is MT per second, So what we're talking about is MT per second, we're talking about megatransfers per second. we're talking about megatransfers per second. So that means the actual amount of data that's being moved So that means the actual amount of data that's being moved not necessarily just the clicks of the clock. not necessarily just the clicks of the clock. But we still have our DDR4 and our PC Speed Rating, But we still have our DDR4 and our PC Speed Rating, when we're talking about DDR4 when we're talking about DDR4 and when we talk about speed ratings and when we talk about speed ratings we use the nomenclature DDR4 and PC4. we use the nomenclature DDR4 and PC4. Like any other type of technology Like any other type of technology RAM has been improving over the years, RAM has been improving over the years, what's important for you is that what's important for you is that when you're picking a particular motherboard, when you're picking a particular motherboard, that motherboard must use a particular type of technology. that motherboard must use a particular type of technology. The newer types of boards tend to use the newest technology, The newer types of boards tend to use the newest technology, but there's plenty of room for older technology RAM. but there's plenty of room for older technology RAM. You'd be surprised how many big laser printers, You'd be surprised how many big laser printers, or dedicated systems still use older RAM. or dedicated systems still use older RAM. Check out any electronics store, Check out any electronics store, you'll see you can still buy DDR2 today, you'll see you can still buy DDR2 today, so make sure you're comfortable so make sure you're comfortable with the different types of technologies, with the different types of technologies, make sure you're comfortable with the pin counts, make sure you're comfortable with the pin counts, and make sure you use the right RAM for your system. and make sure you use the right RAM for your system.