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Old 02-06-2004, 08:04 AM   #12
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Join Date: Nov 2003
Posts: 15
Part two!

Chapter 3 - Heat is not my friend

Ten hours of dual Primes passed so it's time to crank up the speed. I rebooted and set core voltage to 1.450v, saved settings and returned to BIOS.

Prescott seems to be very sensitive to core voltage increases, temperature went up one degree from just +0.05v increase, at default speed and water cooling!

I upped FSB to 233MHz and set memory divider to 5:4. I have four double-sided sticks so it's a very heavy load for the memory controller even at default clock speed. Increasing vDimm actually makes things worse since at higher voltage even less current gets through to physical memory chips!

14*233=3260MHz should be easy and it was, I played more Firestarter and had no problems.

+12v rail dropped a little again, this CPU really does suck up juice!

A rumor from Intel says that the 2.8GHz model originally had a default core voltage of only 1.30v but yields were so horrible that even after at least two core revisions they had to use voltages originally *reserved* (should Tejas fail and large 4GHz+ Prescott yields needed) for 4.0-4.2GHz (!) processors.

Let's test this theory a little, shall we?

Speed/voltage/temp after 15min of dual Prime 95s.
Please note that on air cooling the differences would be larger due to much smaller deltaT.

3.26/1.450 42C
3.26/1.500 44C
3.26/1.550 47C

Need I comment? On my old Northwood systems the differences were much smaller.

Time for a bigger pump - old one had a flow of 700L/h, new one has 1200L/h. I will tell which one I used before results.

Back to BIOS, new FSB=250 divider stays at 5:4.
Boots fine!
Old pump: 3.50/1.550 50C (ouch!)
New pump: 3.50/1.550 47C

One hour of Firestarter+Prime95 passed with no problems.
I hoped for a better improvement, maybe my hoses are too small or my radiator isn't up to task anymore?
Time for a few beers, I need more courage for the next chapter..

Chapter 4 - Real men fear no +20% overvolt, but from what?

I ghosted my boot partition just in case and went back to BIOS.
New voltage: errr what should I use..

+20% from 1.3v? (1.550v)
+20% from 1.4v? (1.675v)

Will I be the first to witness SPDS (Sudden Prescott Death Syndrome)?

I'll make a compromise for now and use 1.60v for now, somebody else can find out wheter SPDS exists/will exist

New voltage: 1.60v, new FSB: 270 save&exit..
Message tells me BIOS is corrupt.
Oh f-uck.

Holding insert and power-cycling brings sanity back to the chips of the beast but dents my courage.. I back down the voltage to 1.575v and memory divider to 3:2.

It lives!!
I'm currently running 14*270=3780MHz at 1.575v, I will let it to "burn in" for 4-6 hours by looping Firestarter demos and running Prime95 at the background.

Temps are as follows:
Old pump: 3.78/1.575 54-55C
New pump: 3.78/1.575 50-51C

+12v rail has dropped from 12.18v to 11.94v, I will adjust after burn-in period.

If I can keep this furnace cool I will try to hit the magic 4GHz barrier, I have never run over 280+FSB so if any of you have tips for very high stable FSB speed I'd be glad for help.

To be continued.. (unless it melts before)