- Everybody wants their computer to be fast, and as a result of that, when you're looking at CPUs everybody thinks that faster is better. So let's talk about speed for a minute. First of all, when we're working with CPUs, CPUs do come with a rated speed. So for example, this particular CPU I have in front of me, runs at-- This is an old Pentium Four, there's a reason we're talking about this. And it actually has printed right on here, 1.6 Gigahertz. Now, a hertz is a time per second, and giga is a billion.
So this can run at 1.6 billion cranks per second in essence. Now the question is, is what's cranking the system? If you see 1.6 printed right on the CPU, it would make you think that there's like a motor in here, or something that's driving this and running it at 1.6 gigahertz per second. But that's not true, what's actually pushing this guy, is the system crystal. Ever seen a system crystal? I got one right here. Now if you take a look at this motherboard, you see right here, this little, little, silver, oval-shaped can right there? That's the system crystal.
The system crystal really is just a piece of quartz that's oscillating at a certain speed. I believe that particular one right there is running at like 20 megahertz. So then there's internal circuitry that pushes it forward. So, the important thing you need to appreciate, is that even though this CPU says 1.6 Gigahertz per second, that's it's maximum speed. I could push this at one hertz, one cycle per second, and it would still run fine. It would still run really, really, really slow, but it would still work.
So, it's important to appreciate that this number that you see here is simply because it passed a certain number of tests. When you buy CPUs, you'll see the exact same make and model of CPU that comes out in two, three, four different speeds. And the faster ones are more expensive. So you'd say to yourself, "Wow, I bet they're coming off of four different manufacturing lines." No, really what's happening is these all come off the exact same manufacturing line, but the ones that pass the higher speeds, pass more tests, that's all there is to it.
So, it's really nothing built into the CPU that makes that speed. It's a matter of how many tests did it pass in order to achieve that. Now, what I want to do, let's take a look at this motherboard one more time. We've got a system crystal down here, but it's running at a very low speed compared to what the CPU itself does. Now granted there's some on-board circuitry that's going to take that 20 megahertz crystal and push it up to, depends on the motherboard. Usually around 200, maybe as low as 100, up to 200 megahertz.
Now the question is, is if the motherboard's only running at 200 megahertz, what's making the CPU run at 1.6 gigahertz? Well, what's happening in here, is you have something called a multiplier. The CPU itself can run a lot faster than your motherboard can. Motherboards just because of the very nature of their design, really aren't designed to run much faster than about 200 megahertz. So CPUs will take that motherboard speed and then they'll increase it, usually by a factor of anywhere from as low as maybe eight up to about 16 or even 20.
And it takes that, multiplies it, and that's where you get that speed from. So if I've got a 1.6 Gigahertz CPU, and I put it on a 200 megahertz motherboard, that means, let me do the math in my head, I have an eight times multiplier, 200 times eight is 1.6, you got it. And that's what clock multipliers are. This is all handled automatically. You'd have to go back in the old, old, old days, and it used to be you'd have to move jumpers and stuff. But today, as long as you've got the right CPU for your motherboard, you just drop it in and you can adjust this stuff.
Now, what's a little interesting, I just want to throw this in as an aside, is that you can buy motherboards that are known as overclocker boards, and what I can do, is I can push this CPU faster than its rated speed. So if this is 1.6, I've got a 200 megahertz motherboard, instead of making it times eight, what if I made it times 10? Now, keep in mind, it's going to be running faster than its rated speed, correct? Nothing wrong with that, other than the fact that Intel would be very crabby.
Because, they put it through a number of tests to make it run at 1.6, and now you want to make it run at two Gigahertz. So that's called overclocking and we'll cover that in more detail in other episodes. But for right now, I want you to appreciate that overclocking simply means to push the CPU beyond its rated speed. The Pentium Four was a very interesting CPU. When it came out, about 10 years ago, a little more than that. The Pentium Four's microarchitecture was designed to have it run at what would eventually be very, very high speeds.
Around 10 years ago we thought we'd be getting up in the area of six gigahertz, seven, eight gigahertz by now. And that the Pentium Four's microarchitecture would carry it along over all those years. Well, it didn't quite work out that way. It ends up that when you start trying to run at really, really high clock rates. We don't really have the technology to do that very very well. I mean we do, but it's expensive. So, what we've started to do instead, is we'll take a single CPU and in essence put, I don't know, two, four, sometimes eight CPUs within one physical chip.
If we can't get much faster, right now getting much beyond say, three and a half Gigahertz is pretty hard. So if we want to get past that, and we can't get faster clocks, so we'll just give you more CPUs. So while this may look like a single CPU, in reality it's either two or four, eight, it depends on what microarchitecture you're using to define what are known as cores. Now, if you want to see some cores in action, let's take a look at CPU-Z one more time.
Alright, so, here I am taking a look once again with CPU-Z. And, I want you to notice down here at the bottom. Well first of all, you'll notice that this tool it says Processor number one, but it's greyed out. If I had a motherboard that could accept two or four processors, I could literally choose a particular one, but that's not what we're talking about. When we're talking about processors here, we're talking about physical chips. But built into this one Core i7 are four Cores, you see it right there.
Now, if you have an Intel product, and in particular it has to be a Core i7, you get another very, very cool feature, which will take one core, and make it look like two cores. And that's called Hyper-Threading. Now for me to show you that, I need to bring up Task Manager. And you'll see I've got Task Manager already preset to the performance tab, and if you take a look right here you can see it, one, two, three, four, five, six, seven, eight.
In essence we have eight cores, now I gotta be honest with ya, really physically we only have four cores, but because we're running Hyper-Threading, because it's an Intel i7, we make it look like eight cores. Clock speeds and cores are an important part of understanding your CPU. Number one, always remember that the CPU itself is actually sold at a particular rated speed. But that speed is driven by the system crystal.
The system crystal pushes out a particular speed, which we call the motherboard speed, which is then multiplied internally by the CPU to get that full speed. The number of cores that you have in your CPU, really depends on how thick your wallet is, more than anything else. It's not at all uncommon to have one particular microarchitecture that can support let's say eight cores, but they'll turn off half the cores for lower priced items, and turn off, down, maybe down to as low as two for even lower cost CPUs. And as a result of that, then the number of cores you get, really depends on how much money you're willing to spend.
Also, keep in mind that Hyper-Threading literally takes one core, and makes it look like, at least to Windows, two cores. So as a result of that, if you see a system and you're running CPU-Z or something like that, you know you have four cores, but then you run Task Manager and all of a sudden you see you've got eight CPU meters, you know instantly that you're running Hyper-Threading. And remember about Hyper-Threading, it's only for Intel, and CompTIA loves to ask that question. (blues music)
The CompTIA A+ 220-901 exam is comprised of six key parts. The first, core processing, is covered by this course. Instructor Mike Meyers explains the fundamentals of PCs, microprocessors, RAM, and BIOS. He also shows you how to set up, connect, maintain, and troubleshoot the main components of a computer.
Note: The six courses designed for the CompTIA A+ (220-901) exam preparation include core processing, core hardware, peripherals and building a PC, displays and printers, networking, and laptops and mobile devices.
We are now a CompTIA Content Publishing Partner. As such, we are able to offer CompTIA exam vouchers at a 10% discount. For more information on how to obtain this discount, please download these PDF instructions.
- How do personal computers (PCs) work?
- What is a central processing unit (CPU)?
- When is random access memory (RAM) used?
- What is a basic input/output system (BIOS)?
- Installing a CPU
- Working with extensions and sockets
- Troubleshooting RAM
- Setting up a BIOS