Clock multiplying

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With an 8088 system the FSB, RAM & clock speed are all synchronous, right? What I’m struggling with is what happens in a modern clock multiplying system.

Theoretical P4 DDR400 system:

FSB 200MHz
RAM 400MHz
Clock 1900MHz
Clock x 9.5

Is the terminology & figures I’ve used correct? Also what is the starting point to understanding the various speeds? Would it be the motherboard specification telling you the maximum RAM speed it supports & then determining the FSB & clock from that?

 

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Have a look at this..

http://www.directron.com/fsbguide.html

Andi

 

To go through a example

Theoretical P4 3.06GHz system:

The Pentium4 3.06GHz
FSB 533MHz
System Clock ~133 MHz (P4's are quad pumped ie FSB/4).
The multiplier ~ X 23 (3,060 / 133 )


Andrew

 

that's very helpful. i was confused over the term clock, it's easier to understand now i know there is a system clock & a CPU clock. have some rep.

 

No problem


Down load CPU-Z

http://www.cpuid.com/cpuz.php

And you can see the data for you own system,


AMD 64 etc adds Hypertransport bus into the equation, which i haven't really seen in A+ materials yet

A PC and CPU are just a load of buses all running at different speeds buffered together. Modern systems don't normally have a clock generator for each they tend to use multipliers and dividers to scale up or down in between.

 

interesting, i ran cpu-z & discovered my multiplier is 6.

core speed 1600MHz
multiplier x6
bus speed 267MHz
rated FSB 1067MHz

the Q6600 kentsfield is quoted at 2400MHz so i would think my multiplier would be 9, does this mean my system is underclocked?

-------

i've checked the bios & the cpu ratio is locked on 'auto', presumably it idles at 6x & ramps up under load to a maximum of 9x.

 

PM'ed you

(Out of A+ scope)

 

As i have just forwarded this link to someone i thought i should add an explanation to the thread, after nearly a year.

I don't know if the 2009 A+ covers this in any more detail.....

the multiplier is showing as x6 not x9, because of the systems power saving / cooling features (namely C1E) are adjusting the multiplier.

you can normally disable these features in the BIOS and the multiplier will go back to x9 in this case.

You also have EIA which if i recall adjusts the voltage

 

what supanova says is spot on.

Just to add there is a method which is called overclocking which is where you make the CPU faster than its rated speed (this voids your cpu warranty if you do it and can shorten the cpus life span).

My cpu is rated at 3GHz which is an FSB of 333 x 9 I have my cpu running at 443 x 9 which makes my processor run at 3.91GHz I switch of settings such as C1E and Intel speedstep. The reason why your cpu is slower than what it is supposed to be is because those settings are enabled to save power and heat.

When you are browsing the internet or typing a letter the cpu throttles down to a speed that is needed but when you do something like play a game the speed increases to what it should be.

Some people when overclocking raise the FSB more but decrease the clock multiplier to try and get more out of the cpu

If you are ussing ddr2 ram then the ram speed should be double the FSB speed this gives the ram a 1:1 ratio and means it is fully running in synchnoros mode so again my FSB is 443 so my ram is running at 886 although my ram can run at 1066, 886 is better.

The motherboard manual should tell you everything you need to know so for instance my motherboard can run ram at 667,800,1066 and has FSB speed as 1066 or 1333 for the cpu.

PS I dont advise overclocking if you do not know what you are doing.

 

HyperTransport
http://en.wikipedia.org/wiki/HyperTransport

[removed i wasn't happy with what i have written , i'll rewrite sometime]