Calculating memory frequency..

grndnatnl

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Oct 3, 2006
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I've been beating myself over the head with this for a while and can not figure out the formula.. I suck at math, so maybe someone can better explain this to me.

This is part of a paragraph in an internet article about A64 OC'ing in relation to memory, etc..

"For all intents and purposes, the memory divider is merely a ratio of HT bus speed to memory speed. The 200 MHz option is a 1:1 ratio, meaning that an HT bus speed of 200 MHz will yield a memory speed of 200 MHz. The next most common option is 166 MHz, which is a 6:5 ratio. If your HT bus speed is 200 MHz, and you use this ratio, you will get a memory speed of 166 MHz. It really is quite simple, but you will most likely need a calculator to do some calculations once you're tweaking things. For instance, using the 166 MHz divider (6:5), you have to run your HT bus at 240 MHz in order to achieve the standard 200 MHz memory clock again...."

My question is, how the heck do I calculate this ratio myself? Having a problem figuring out the math for my current settings. If my HT in this case is 260 (CPU @ 2.60 Ghz), and with my current [temporary] DDR400/200Mhz RAM I have to lower it to DDR266/133Mhz in the BIOS, and during POST it runs at 173 Mhz.

What do I multiply the 133 by to get 173? How do I calculate what the memory will run at for a given CPU or HT freqency? For example, what if I bumped it up to 270 (2.7 Ghz).. What would it be then; how much closer to the rated 200Mhz?

TIA
 

Sunburn

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Call your old math teacher. Apologise for being lazy. Ask him to do the math. Problem solved.

Then again, your BIOS may the math for you. Depends on your moboard.
 

grndnatnl

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lol.. I know its not really that important because its just trail until error then take it down a notch. I just like to have a better understanding of how the calculations are being made so I know whats happeneing memory wise, and what I'm looking at each adjustment.

Thanks for the link. Had to manipulate the link to the actual file a little but I got it.
 

niz

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Feb 5, 2003
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I've been beating myself over the head with this for a while and can not figure out the formula.. I suck at math, so maybe someone can better explain this to me.

This is part of a paragraph in an internet article about A64 OC'ing in relation to memory, etc..

"For all intents and purposes, the memory divider is merely a ratio of HT bus speed to memory speed. The 200 MHz option is a 1:1 ratio, meaning that an HT bus speed of 200 MHz will yield a memory speed of 200 MHz. The next most common option is 166 MHz, which is a 6:5 ratio. If your HT bus speed is 200 MHz, and you use this ratio, you will get a memory speed of 166 MHz. It really is quite simple, but you will most likely need a calculator to do some calculations once you're tweaking things. For instance, using the 166 MHz divider (6:5), you have to run your HT bus at 240 MHz in order to achieve the standard 200 MHz memory clock again...."

My question is, how the heck do I calculate this ratio myself? Having a problem figuring out the math for my current settings. If my HT in this case is 260 (CPU @ 2.60 Ghz), and with my current [temporary] DDR400/200Mhz RAM I have to lower it to DDR266/133Mhz in the BIOS, and during POST it runs at 173 Mhz.

What do I multiply the 133 by to get 173? How do I calculate what the memory will run at for a given CPU or HT freqency? For example, what if I bumped it up to 270 (2.7 Ghz).. What would it be then; how much closer to the rated 200Mhz?

TIA
Jeez you guys... 173/133 = 1.3008
What are they teaching you at school these days?
 

4745454b

Titan
Moderator
Brake out your calculator built into windows. Lets see if you can follow this.

6:5 is a ratio between your memory and your HT bus. If your running your HT bus at 200MHz with this ratio, you can multiply 200 by 5, then divide by the 6. (200 x 5) / 6 = 166. The same is true when you move to 240. (240 x 5) /6 = 200.

Knowing which ratio you need to use really only helps when your motherboard lists the ratios instead of the frequencies to use. Most motherboards of today list the frequency you want the ram to run at, 400/333/266, etc. Few if any list what ratios are possible. Does it really matter to you if your ratio is 11/16? Just set it at whatever the highest stable frequency is and don't worry about the ratio.
 

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