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Help with FSB Please!!

Last response: in CPUs
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September 9, 2004 11:26:40 AM

Hi!

Can anyone help me solve this confusion?

(sorry about my bad english :p )


I'm using a Pentium 4 @ 1.7 GHz. wiht 400 MHz. FSB

I have this motherboard: Intel Desktop Board D845GLLY

And the specs are:

This MotherBoard is designed for Celeron and Pentium 4 processors

The FSB is 400 MHz.

And uses PC133 SDRAM (It's TRUE... ordinary SDRAM, NOT DDR!!!!)

HOW THE HELL CAN IT BE???


I've read in some web pages that the Pentium 4 uses a FSB with one of the following speeds:

Pentium 4 A : 400 Mhz. FSB Speed = 4 (quad pumping) x 100 MHz. (System clock speed)
Pentium 4 B : 533 Mhz. FSB Speed = 4 (quad pumping) x 133 MHz. (System clock speed)
Pentium 4 C : 800 Mhz. FSB Speed = 4 (quad pumping) x 200 MHz. (System clock speed)

But I have a few questions:


where in the hell the system clock is?
on the motherboard maybe?

Then, How the RAM can operate at a different speed?
the ram has its own clock?

This question remembers me this other:

I've read that RAMBUS RIMM is is only double-pumped but it's very fast,
so it does 2 cycles when the FSB does 1 and in this way compensate the difference.

Again the same question:

How the RAM can operate at a different speed?
the ram has its own clock?

Why they say "The processor have the 400 MHz FSB?
the processor has its own clock or it's the same one of the MotherBoard?
the processor could be at different FSB speed than the MotherBoard?

My MotherBoard was designed like this by some kind of STUPID guy or what?
there is a huge bottleneck in my system?

THANX

More about : fsb

September 9, 2004 11:42:55 AM

The Mobo clock will be 100Mhz, it will be quad pumped and multiplied on the chip do derive youy 1.7Gig operating bandwidth.

The same Motherboard clock will be scalled differently to provide Ram clock, but will be syncronised with the CPU (being derived from the same source)
Your Pa A,B,C info is correct regarding FSB.

The processor has to execute many simple instructions to perform a basic high level instructions. And may take an average of 4-6 clock cycles per instruction, so memory speed does not need to ba no where near as fast to keep pase. but as CPU speed increases, so does Memory speed to keep the effective performance ratio the same.

The higher the speed on the mobo, ie running 400Mhz say would require very tight timings between i/o channels, hence processor it's self scales the frequency.

With 200Mhz Mobo clocks and high speed DDR, these are already putting a strain on Mobo desing, matched trace lengths, matched impedances...

The only real bottle neck is the CPU, it's got very little onboard memory (256k vs 512 of a Northwood) and has to do a lot more swaps of data to and from the SDRAM you have on the MoBo,

So what's the real problem, you pissed with the performance?

MIS645Ultra/P42.4@2.8Gig/2*Corsair 256MBit CL2-2-2-7XMSLLPT PC3200 DDR RAM/450W Enermax PSU/1*40Gig 7200rpm Wes-Dig/1*20Gig 7200 Hitachi Disk/GeF4 Ti4200 XFX Turbo 670/250 Ram/Core MHz.
September 9, 2004 12:01:58 PM

Thank you sooooooo much.

Well, I'm not pissed off with the performance cuz this machine was an emergency buy. (cheap in a hurry) :p 

I just wanna know why is my RAM running with a different speed than my MotherBoard FSB.

The important points are:

IS THERE ONLY ONE SYSTEM CLOCK AND IT'S ON THE MotherBoard?

This system clock is used for the RAM with some kind of divisor?

is that right?
Related resources
September 9, 2004 12:06:58 PM

CPU and RAm clocks are derived from a single mobo clock. This ensures syncronisation.

MIS645Ultra/P42.4@2.8Gig/2*Corsair 256MBit CL2-2-2-7XMSLLPT PC3200 DDR RAM/450W Enermax PSU/1*40Gig 7200rpm Wes-Dig/1*20Gig 7200 Hitachi Disk/GeF4 Ti4200 XFX Turbo 670/250 Ram/Core MHz.
September 9, 2004 12:15:26 PM

Got it!

It's clear now.

thanx Mitch007
!