Basic CPU knowledge

[Cyrus]

After years I'd known that: bus x multiplier = clockspeed, I just realized that I still don't know what multiplier really is. And I've got the picture of what bus, FSB and HyperTransport are, but I'm not quite sure exactly about them.

Would anyone mind telling me what they really are?

 

[fishmahn]

The multiplier is just a part of the cpu that makes a secondary clock that ticks multiple times per clock tick from the motherboard. That's how you get a 3+ghz processor speed on a 200mhz fsb.

A bus is a large vehicle used to transport a good number of people long distances over paved roads... oh, not that kind of bus, sorry....

In this context its a 'highway' for data and communications between devices. i.e. the PCI bus lets modems, sound cards, etc. communicate between themselves and the rest of the computer.

FSB = Full service bank... something missing that I remember from when I was a little tyke... oh, sorry.. got carried away...

Front-side bus. That's the bus for communications between the CPU(s), memory and the rest of the computer, usually controlled by the Northbridge.

HyperTransport is a type of Front-side bus used by Athlon64 CPUs. It runs at a multiple of the mobo generated FSB speed.

Mike.

 

[Cyrus]

Thanks for the nice explanations.

So the chip does tick in Ghz. That's scary, I thought multiplier was a paralelism thing.

Still left me one question though. While having the same clockspeed, how can a processor with higher bus is faster than one with more multipliers?

 

[Guest]

Higher bus will give you more bandwith. Some processor are somewhat "starved".
That usually means that the frontside bus is some sort of a bottleneck. In that case the memory cannot send data to the cpu fast enough. So the cpu is just sitting there waiting for data and not being fully used.
In the end, different cpu works differently. So some cpu might need more bandwith than other so they will need a faster FSB to perform equally well. But most of the time youd rather have a 200mhz X 10 = 2ghz than 100mhz X 20 = 2ghz.

Asus P4P800DX, P4C 2.6ghz@3.25ghz, 2X512 OCZ PC4000 3-4-4-8, Leadtek FX5900 w/ FX5950U bios@500/1000, 2X30gig Raid0

 

[Cyrus]

I see. Thank you so much. ^^