Confused on speed

[tekbro]

(Not read: "Confused. On speed.")
In any case, I need some help on setting up my upgrade. I've tried to figure this out, but can't quite put it all together yet. Here are my specs:

Mobo:Matsonic MS8188E fATX, Via KM400A, FSB=133MHz
CPU: AMD Athlon XP 2000+, (1667 MHz). Sys FSB=266MHz
RAM: Apacer DDR PC2100 DIMM

First, I'm unclear on the relationship between The RAM, mobo, and CPU speeds. The mobo manual has a jumper (J3) setting of 133, 166, 100, or 200 MHz to select CPU Clock freq. BUT, my CPU specs only give a system bus speed of 266 MHz! I guess I'm not sure which jumper setting is correct. Also, my mobo manual says it support UP TO 2GB of DDR333. Does this mean I can't use DDR133 or DDR266?


-Tekbro

(forgive me, but I mistakenly posted this in the Memory forum. I intended to post it here...unintentional cross-post.)

 

[jammydodger]

Ok first off DDR stands for double data rate, this means it sends data on the rising and falling edges of each clock cycle. There for it will send twice the ammount of data than SDR of the same speed.

DDR266 is technically running at a bus speed of 133Mhz however because it is DDR it is sending twice as much data than SDR so they call it 266. DRR memory can also be referred to by its memory bandwidth, this is the bus speed multiplied by the bus width.
e.g.
133mhz*2(DDR)*8bytes = 2128 or PC2100

Does this mean I can't use DDR133 or DDR266?

DDR133 does not exist as far as I know. But you will be able to use 2GB of DDR266 without a problem...why you would want to is another question.

So some up, you FSB is 133Mhz, but its transferring twice that between both the CPU and northbridge and the memory and northbridge. Therefore you could say you have an FSB of 266 Mhz.


P4c 2.6@3.25
512Mb PC4000
2x120Gb 7200.7 in RAID0
Waterchill KT12-L30
Abit AI7
Ge-Force4 Ti4200

 

[Crashman]

Easy answer, 133MHz is the clock rate for a DDR266 bus. That "266MHz" number is a DDR number for both the CPU and RAM busses on your system. So you might see them used interchangably (many boards show a 133MHz CPU bus and 266MHz memory bus, when both are really 133MHz clock, 266MHz data rate).

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[tekbro]

OK, I think I'm getting there. So far, I gather there's two frequencies to deal with: The system clock or FSB, and the system memory bus.

My mobo chipset is Via UniChrome KM400A, and according to <A HREF="http://www.via.com.tw/en/apollo/km400.jsp" target="_new"> VIA </A>supposedly it supports FSB freqs of up to 333MHz, and can support DDR speeds up to 400. So, to me it's still not clear how the multiples work out to give you the right system clock setting. Which standard fundamental frequency should one use in comparing/selecting the proper system clock setting? (33Mhz, 66 MHz, 100MHz, 133MHz, or what?) It's not clear what you divide 333 by to give you the correct multiple of base frequency.

 

[Crashman]

There are 4 possible bus frequencies you have to deal with on your board:
1.) The actual bus clock of the CPU. The maximum approved for your chipset is 166MHz.
2.) The DDR rate AMD uses for advertising their CPU busses, the CPU is on a DDR bus just like the memory. Double Data Rate as 2 transfers per clock cycle, so 166MHz bus clock is "333MHz" using that method
3.) The Memory also has an actual clock frequency, the limit approved for your chipset is 200MHz clock rate.
4.) your Memory is DDR, so 200MHz is called DDR400, or simply 400MHz.

It may or may not be meant to confuse you, but 166=333, 200=400, and BIOS values can use either. Recent boards have used the actual clock frequency for the CPU bus value, and the DDR rate for the RAM, where you see them in the BIOS menu.

Many people find their systems run better when the memory and RAM are running at the same speed, aka "synchronously". With most boards this is called 166MHz CPU bus and 333MHz RAM frequency, where the first number is an actual clock rate and the second a DDR number.

Now the multiplier works off real measurable clock frequencies, not soft values, so if you divide a 333 bus CPUs ACTUAL clock rate by 166 (not 333) you get the multiplier.

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