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What is the Mhz Stepping for Fermi? GTX 200 series is 27Mhz

post #1 of 2
Thread Starter 
I'm trying to find the number the clocks go into evenly for overclocks. Since I can set 800Mhz and EVGA and AIDA report if I remember correctly 797 or 798Mhz. I think the stock clock is 607Mhz so I need to find out what the correct steps are so I can dial in the correct clock for the overclock.

For instance the GTX 200 Series has 27Mhz clock stepping. So say I set 750Mhz it will just clock it to what it can produce by it's clock generator to 729Mhz. I figured out with tons of testing the ideal clock stepping is 27Mhz since 27Mhz goes into 729Mhz and 756Mhz. So the GTX 200 Series can only truly run at either 729Mhz or 756Mhz because 729 goes into 27, 27 times. The same applies to 756Mhz since 756 goes into 27, 28 times.

I can't quite find the ideal number on the GTX Fermi series or the 400 series in particular. Right now I'm running 835Mhz and EVGA and AIDA64 report it correctly at exactly 835Mhz.

So if any of your guys are good at math, you could find the number that evenly goes into 835 without any decimal points. It has to be an exact number. Like for instance I thought it was 12 or 13mhz but it seemed to change dynamically as the clock went up so I'm not sure at all.

I'll do some more testing to determine the exact number. I'll write to bios 840mhz, or 845mhz and find what number it actually reports since we're are calculating the stepping number the clock generator will produce. You can write any number to the bios but the Fermi Clock Generator will only produce what stepping is closest in it's Clock Generator Table.

Thanks
Edited by chris89 - 6/6/13 at 7:59pm
post #2 of 2
Thread Starter 
I figured it out.

So I figured out the multiplier is actually 0.1875 which is odd huh?

So basically any number with .1875 will result in the correctly produced clock via the FERMI clock generator.

For instance 850mhz resulted in 851mhz. So i did 851 minus 835 and got 16. So I then did 835 divided by 16 and got 52.1875. I then did 851 divided by 16 and got 53.1875. So basically any number you want just do 16 times say 54.1875 and that gives your correctly produced clock via the clock generator of 867.

So setting any number not an exact multiple of 0.1875 will only produce the clock closest to the set value via the clock generator.

wink.gifbiggrin.gifthumb.gif
Edited by chris89 - 6/6/13 at 8:40pm
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