Memory FSB help please

[Luis]

Hi!

Can anyone help me solve this confusion?

(sorry about my bad english )


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

 

[folken]

Pentium systems are crazy I know. I'm an AMD fan myself so I never have to deal with that stuff but I'll take a stab at explainin it anyway.
The 400mhz system bus is the speed of the bus between the cpu and ram. This may seem like a bottleneck because the CPU's FSB is only 100 and the ram is 133 but it isn't. The pentium systems just cram more data into every clock cycle so it seems like the system bus is running at higher speeds.
The ram isn't running at higher speeds, more data is just getting cramed into every cycle of the ram.
In other words they are sort of liein to ya bec those really arn't the speeds of the FSB, they are just calling it that bec it is doin more per clock cycle so it is supposidlty equal to 400mhz fsb or what ever.
That probably wasn't the best way of explaining it but oh well. That at least gives a general idea of it.

<A HREF="http://www.folken.net/myrig.htm" target="_new">My precious...</A>

 

[Crashman]

The bus clocks are split at the chipset. The 100MHz CPU bus (uses quad data rate for 4x the transfer rate) goes from the CPU to the memory controller, then the 133MHz RAM bus goes from the memory controller to the RAM.

Because the CPU bus has 4x the transfer rate of it's clock speed, even DDR200 (100MHz bus with 2x the transfer rate) can't keep up. DDR400 could with your OLD processor, but newer processors have even faster busses. That's why todays performance boards use a pair of DDR400 to creat a bus 2x as wide.

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[RichPLS]

Unique setup there folken.


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[Luis]

Yeah Crashman!!!

That's exactly what I want to know.

So let me see if I understand:

THE CPU sends data at 400 MHz to the memory controller.
(400 MHz. = 100 (system clock) x 4 (quad pumping)

And then the memory controller sends the data to the memory
at the speed that memory supports.
(In my case is 133 MHz, because my sdram is not DDR SDRAM)

Now, it seems that there are 2 buses:

One goes from CPU to Memory controller
and other goes form Memory controller to RAM

Is that right?
How are they called?
their speeds are derivated from the system clock or there are various physical clocks, one for each bus?

A guy in this community tell me that there is only ONE system clock and all buses speeds are derivated from the system clock by means of multipliers and dividers.

I really appreciate the help from this guy, but as you can see, I'm a newbie and in top of that I don't understand english completely so that's the reason I want to read as many explanations as possible (in the easiest words).

Thank you.

 

[Crashman]

"System bus" used to refer to the CPU and RAM bus combined, but since they went to split speeds it now refers to the CPU to chipset bus (including CPU to memory controller).

Everything is based on the clock generator, memory and RAM frequencies are alway in a proportion. For example, a CPU bus clock of 100MHz and RAM bus clock of 133MHz are a ratio of 3:4.

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[jammydodger]

As crash said, every bus speed is based on a clock generator called the PLL (Phase Locked Loop). For example is the PLL is giving a 100Mhz signal then your CPU-northbridge will run at a 1:1 ratio with the PLL while the RAM will run at a 3:4 ratio with the PLL.