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Bus Speed and RAM

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a b V Motherboard
August 17, 2001 12:18:02 AM

Right now I'm running a intel PIII 600 at 100 Mhz/bus and soon I plan on upgraded my CPU and Motherboard, but I'm a little confused what to get. My question is that if I ran my FSB and overclocked it 2 say 133 and I had PC-100, wouldn't that essentially be overclocking my SRAM. I don't have this problem, but I'm using it as an example. Some of the new MOBO have 200/266 bus speeds how are they not overclocking the RAM, I'm aware that they make PC/100/133/150 but how do you run at these higher speeds. I might be wrong, but I thought that SRAM is dictated by the system bus speed, I'm confused do these boards use DRAM, does that work independant of the bus, or what? I hope not because I'm trying to go the economical route. thanks.

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a b V Motherboard
August 17, 2001 1:50:22 AM

The 200/266 is a flase number, it refers to the DDR bus from an AMD chip to the northbridge of the motherboard. Most AMD motherboards still use SDR memory, thereforn since the memory bus goes from the northbridge to the memory, 200 is 100 and 266 is 133.
Memory is cheap, get some PC133 for your current system and overclock it to 133FSB for free. Total cost for the new memory will be between $10 and $50 in the U.S. Overclocking will bring your processor to 800MHz and effectively make it operate as an 800EB.
Chances are your memory is already PC133 if your computer is less than 2 years old. PC133 is cheaper, and is often relabled as PC100.
You may have to raise your core voltage slightly to overclock. You may also need a better cooler. The VolcanoII is only $8 and is more than good enough for your system.
If you need any help oveclocking, tell me your motherboard and I'll give you all the information you need.

I'm so tired of cookies I'd settle for spam!
Anonymous
a b V Motherboard
August 17, 2001 4:41:37 PM

I'm confused how the northbridge only runs at half the motherboards bus, then why is the number not 100/133 instead of 200/266. I new to this so I really don't know what the northbridge is anyway. I appreciate your info, could you fill me in a little more. I do plan on overclocking my current FSB and memory, but I'm on vacation away from my school computer so I don't know the specific details mobo ect.. , but I'll let you know shortly. Also I bought a "High-Performance CPU cooling Fan" from Radio shack it has a fan speed of 5000Rpm and a heatsink, would this be ample cooling or should I return it and go for the volcanoII. thanks.
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August 17, 2001 5:55:52 PM

200/266 MHz is the DDR FSB used by AMD Athlon and Duron processors. it is not really 200 or 266 MHz but is just the same 100 or 133 MHz. but important thing is that these processors do twice the amount of work in a single clock cycle of this FSB, they transfer data twice each cycle, while the P-III bus does it just once. in fact all traditional CPUs, even older AMD CPUs did this.

so, in <i>effect</i>, the Athlon and Durons transfer data as if the frequency was 200 or 266 MHz. hence its said 200/266 DDR - thats Double Data Rate!

if you use standard SDRAM instead of DDR-SDRAM, you arent really using this extra bandwidth since this DDR link is restricted just to the Northbridge which, then connects to the main SDRAM memory at Single Data rate.

BTW SDRAM is not Single Data Rate memory (although you can say it is!) but is Synchronous Dynamic RAM. all DDR RAMs are synchronous hence they are called DDR-SDRAM.

and no, rest of the motherboard does not run at 200/266 or even 100/133 MHz. in fact it runs much lower than that, 12, 33 or 66 MHz!!!

girish

<font color=blue>die-hard fans don't have heat-sinks!</font color=blue>
August 17, 2001 6:16:31 PM

the FSB is the all important value of frequency on the motherboard. all other frequencies are derived from this.

of course, some chipsets allow you to decouple CPU and memory speeds so that you can use a CPU with 100 MHz FSB and PC133 memory and both will run at their rated speed, while you can also use a 133 MHz FSB CPU along with a PC100 memory.

traditionally the FSB is a multiple of 33 MHz, and hence the PCI bus speed is derived from the FSB by dividing it by 2 (66 MHz FSB, older P-IIs and Celerons upto 766 MHz) or 3 (later P-IIs, Celerons from 800 above and P-IIIs upto 850) or 4 (P-IIIs from 667 MHz above) or even 5 (for overclockers who run their FSB upto 166) these days.

and if you set the FSB to some non standard value like 120 MHz, you can run your PCI at 40 MHz, slightly overclocked. but not all PCI devices run reliably over 33 MHz but most of the newer ones will! the AGP runs at 66 MHz and it could be overclocked to 80 MHz or so.

If at all there is any ISA bus, it is derived from the PCI bus speed, dividing it by 3. so at times even the ISA bus could be overclocked to 13.3 MHz!!

and regardless of the processor FSB or memory speed, the timer clock stays at 1.91 MHz and it is so for last twenty years!

girish

<font color=blue>die-hard fans don't have heat-sinks!</font color=blue>
August 17, 2001 6:36:10 PM

Quote:
RE: JamesHill: <font color=green>“I'm aware that they make PC/100/133/150 but how do you run at these higher speeds.” </font color=green>

Just a quote from <A HREF="http://www4.tomshardware.com/howto/01q3/010725/bios_tun..." target="_new"> Tom's Hardware Guide:</A>
<i><font color=blue>“Useful information: A memory module at 133 MHz clock in CL2 mode is faster than an overclocked module operating at 150 MHz in CL3 mode! “</i></font color=blue>


RE: girish: Thank you for your interesting and very informative articles.
a b V Motherboard
August 17, 2001 9:27:31 PM

I think girish explained it well, basically, 200 and 266 are not REAL clock speeds. The are ACTUALLY 100 and 133. DDR is a technology used to pass two bits instead of one bit per clock cycle. Because data passes at twice the rate, AMD decided to call it 200 and 266, which is not a truthfull number and has managed to confuse millions of people, hundreds of whom have addressed this question in here.
Now, about the Radio Shack cooler, don't open it, return it, it's garbage. Get the VolcanoII, it's available from <A HREF="http://www.nexfan.com" target="_new">http://www.nexfan.com&lt;/A> for only $8!

I'm so tired of cookies I'd settle for spam!
Anonymous
a b V Motherboard
August 17, 2001 11:25:01 PM

thanks fellas, I think I got it now, One more question pc-2100 and 2400 ram what do these run at 150/166? So only if you overclocked your FSB to say 150 would you see the benefit from them.? And finally if my mother board supports 133 anyway and my cpu fsb is 100 how high do most of you get these chips to run at? I know it is determined by the quality of chip, but can you get 133 fsb, lower higher? If you get below 133 say 118 or whatever the setting my be, how does this effect the other peripherals if they are not running at a standard speed? I guess that was more than one question. Also, I returned the radio shack crap and have a volcano coming my way.
Anonymous
a b V Motherboard
August 17, 2001 11:29:24 PM

never mind scratch those questions, after re-reading you post I understand. So if you have a intel processor it is point less to get the ddr, because the amd will only make use of this feature? correct? thanks.
a b V Motherboard
August 17, 2001 11:36:18 PM

You would need a new motherboard to support DDR, and DDR does not help the P3 anyway. The PIII 600E (that's the one with 100FSB) can get to about 150-166FSB, depending upon the motherboard and RAM. What motherboard do you have?

I'm so tired of cookies I'd settle for spam!
Anonymous
a b V Motherboard
August 17, 2001 11:38:02 PM

one more question do you have to have a mobo that supports ddr or will it fitinto any sram slot, i don't think it matters in my case, just curious.
Anonymous
a b V Motherboard
August 17, 2001 11:45:12 PM

you mean to tell me I could possible get my 600 to run at 900 or higher? my multipler is 6 so 150x6. How would this effect my sram can it be over clocked 2 150 if it is pc133, its crucial if i remember correctly. Not sure what my motherboard is, I'm away from my school cpu, i'll let you know tommorrow so we can rap about it. thanks.
Anonymous
a b V Motherboard
August 17, 2001 11:47:15 PM

900 , damn that would be bad ass!
!