undervolting 2100+

greeef · Post by **greeef** » Mon Aug 16, 2004 8:31 am

just had a quick experiment in undervolting - got 667MHz with a 2100+ at 1.275V, wouldnt boot any lower.

Are there any tricks i'm missing? I'm using an NF7, under load my temperatures are about 10 degrees above ambient with a slow 120mm fan blowing onto a coolermaster "silence" heatsink with no fan, nothing special.

griff

POLIST8 · Post by **POLIST8** » Mon Aug 16, 2004 9:14 am

What's the lowest voltage you can run at the stock speed?

Post by **Rusty075** » Mon Aug 16, 2004 9:59 am

I would try running 8rdavcore.

That way you can boot at stock speeds, and then underclock/undervolt once it's fully loaded. I've found that that method will often allow you to get to voltages below where it will boot at.

The prog also has the benefit of being able to crank you back up to full speed if you run something CPU intensive.

silvervarg · Post by **silvervarg** » Tue Aug 17, 2004 5:16 am

just had a quick experiment in undervolting - got 667MHz with a 2100+ at 1.275V, wouldnt boot any lower.

Is that by chance 11*60?
I have a few wild guesses. Going with a very low FSB might cause your RAM to get into problems. I guess that the refreshrate could become too slow. Changing the voltage to the RAM could help, but changing the RAM vs FSB ratio is probably better.
An even better option is to lower the multiplier a lot and keep FSB higher and RAM on 1:1 with FSB.

Post by **Rusty075** » Tue Aug 17, 2004 5:23 am

silvervarg wrote:Is that by chance 11*60?

More likely 5 x 133. 5 is the lowest multiplier the NF7 will allow.

silvervarg · Post by **silvervarg** » Tue Aug 17, 2004 5:34 am

Well, if it is 5*133 I think he would be very unlucky if he can't boot that chip at vcore 1.200.
With a low multiplier I guess it is just the CPU that could possibly stop you from booting with stability, right?
Greef, can you please confirm the multiplier and FSB settings?

Post by **Rusty075** » Tue Aug 17, 2004 6:02 am

I don't know if I would consider hitting the wall at 1.2v to be all that unlucky. It seems to be about average for where most non-mobile chips start getting flaky. That is a greater than 25% undervolt after all.

The root cause may also be as much with the mobo as with the CPU. The lower the vcore goes, the less headroom the CPU has to deal with fluctuations in the power delivery system. At 1.6v a 0.05 fluctuation probably won't cause a crash, but at 1.2v it's much more likely too. I would venture a guess that VR fluctuations are more common at bootup than at any other time, what with all the other devices suddenly drawing spikes of power through the motherboard.

But even if [email protected] is the lowest it'll go that's still a huge accomplishment. You've cut the heat output by more than 80%!

You are now producing less heat than a Pentium 133 did!

greeef · Post by **greeef** » Tue Aug 17, 2004 8:34 pm

wow, i thought it was drastic, didnt realise it could be an 80% reduction. I think i should try booting cold and seeing if that makes a difference, or at least modding my super cold cooler on properly.

Yes i am at 5x133, i just enjoy having memory bandwidth. I believe my motherboard undervolts my cpu a little compared to what i set it at, and my ram is overvolted. Questions!

1) Does reducing FSB make things easier for the chip at low voltage, or is overall clockspeed the only factor?

2) silvervarg, do you suggest upping or lowering the ram voltage? it's at 3V real atm, doesnt get warm with heatsinks.

3) any tips to getting 8rdavcore to run stably with my mobo: I've simply had troubles, it crashes every time the fsb is altered. My windows install isnt entirely stable though, perhaps i should do another before tinkering more.

polist8 - i dont think i've even booted this chip at stock, but i'm NOT using my good cooler, cos it doesnt like being horizontal yet.

griff