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# CPU

Registered User
edited June 2011
Hey everyone,

I've been lurking on this forum for a while now and I finally decided to make an account.

I want to learn more about how computers work so I am doing a lot of research on this topic.

I've been reading a lot about CPUs lately but there a few things I learned that I'm not entirely sure about.

Let's say I have a 3.4Ghz processor that's 64bit.

So my cpu would have a bus speed of 3.4Ghz and a bus width of 64bit.

That means that my CPU can send 3.4GB of data every clock rate.(Which is every second I understand)

However because the CPU is 64 bit I can process more because I have to apply the formula: bus speed X bus width.

64bit = 8bytes

So my 64bit, 3.4Ghz cpu can actually send 3.4Gb X 8 bytes of data in one clock rate whic would be 27.2GB.

Does that mean that my CPU can actually send 27.2GB of data in one clock rate?

P.S. - I know there are other factors that limit speed like ram, GPU etc but I just want to know if the above is correct as in the CPU could send that much data in one clock rate.

Thanks,

AlexHawk on

## Posts

• Registered User regular
edited June 2011
What do you mean by "bus speed?" Modern CPUs don't have a front side bus anymore and memory controllers are built into the CPUs now as well.

On top of that Intel's Sandy Bridge CPUs & AMD's Bulldozer CPUs could actually be labeled 256bit CPUs at this point.

Right now the hardware is in transition and you're going to have a lot of reading to do.

Dark Shroud on
• A collection of mediocre hats Seattle, WARegistered User regular
edited June 2011
I think more important than trying to calculate memory bandwidth is to just consider your usage pattern. Such as, if it will be used mostly for gaming, look into gaming benchmarks for CPU's in your price range.

Not that it's not a good thing to understand the workings of a modern CPU, what Hypertransport and QuickPath actually do, why cache is a good thing, etc. That's really interesting stuff.

But in practical terms, things like memory bandwidth doesn't often become the bottleneck for gaming, but may very well be the bottleneck for server applications or workstation / CAD / video editing type stuff. Different workloads stress CPU's in different ways.

Also, just to be sure you understand, 3.4Ghz means 3.4 billion clock cycles per second. Roughly 3.4 billion instructions per second (ignoring things like pipelineing and out of order execution and other complexities which change Instructions Per Clock higher or lower). But the CPU and the memory controller often run at different speeds. If you did want to calculate memory bandwidth, you'd need to look at the speed of your memory, not your CPU.

Or you could just use benchmarking software. I even think MemTest86 will display memory and cache bandwidth.

Monkey Ball Warrior on
"I resent the entire notion of a body as an ante and then raise you a generalized dissatisfaction with physicality itself" -- Tycho
• Registered User regular
edited June 2011
none of which is actually at all useful to know in a void.

Are you interested in the Engineering side of CPU's? If so, what you're talking about will be a side-effect of the sorts of things you would need to know and be able to do. And you should probably be a genius too. Seriously. There are a handful of jobs in the world for designing processors.

If you are interested more in the professional side of working with or on computers, then you are definitely reading the wrong things, as fascinating as they may seem.

Darkwyndre on
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