higher dothan clock = slower superpi [Archive]

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08-31-05, 08:56 PM

I just built a dothan rig using the CT-479 adapter, p4p800SE mobo, and a 1.6 ghz 533FSB dothan. I've had no trouble booting and loading windows at 2.4 ghz but am getting a suprisingly slow 34 seconds in superpi (expected under 30 seconds). The issue gets even stranger because increasing the clock further, to as much as 2.6 ghz, results in slower superpi times in the 38 second range. I'm thinking the problem might be voltage drop from this crappy 250 watt PSU I'm using, but I'd like your input. Thanks in advance.

Prodromo

08-31-05, 09:13 PM

Yes that is definately a PSU problem my friend.

08-31-05, 10:39 PM

Thanks guys. I'll have to go pick up a different PSU tomorrow. I never would have tried the 250w except that it's a dothan rig, which I thought would use only small amounts of power.

johan851

08-31-05, 10:43 PM

The CPU does use a lot less power, but after an overclock you're still using a fair amount of wattage. The RAM, hard drives, video card, etc. are all going to use quite a bit of power as well.

Seeing as it's a Dothan and not something like a Prescott, you should be able to get by with a quality 350-400w PSU. Still, a 400w+ PSU would be recommended for most overclockers. I think the 500w BlueStorm (460w actual) would be a great choice.

09-01-05, 10:06 AM

I was sure a new PSU would solve the problem but i just put in a 450w unit and am still encountering the same problem!!! What's also strange is that my Sandra scores are fine and rise as expected with additional speed. It's only superpi that's giving me a problem.

09-01-05, 01:20 PM

I've now found that running the RAM at a 4:5 ratio (causing it to run at a much higher speed) improves my superpi times by 3-4 seconds. This is odd because I was under the impression that RAM had little to do with superpi times. In addition this 4:5 ration limits my overclock because my RAM can only hit about 260, yielding a FSB of only 210. Running at the 1:1 ratio I would like results in these terrible superpi times. Any ideas?

BrianH2O

09-01-05, 04:54 PM

PM's love bandwidth ....

I can run at the following 1:1 speeds

9 x 305 ---> limit of my ram , 3-4-4-10
10 x 280 ---> limit of my CPU, 2.5-3-3-6
11 x 250 ---> CPU 2.5-3-3-6
12 x 230 ---> CPU, 2-2-2-5
13 x 215 ---> CPU, 2-2-2-5
14 x 200 ---> CPU, 2-2-2-5

All are around 2.8ghz, the fastest is the 10 x 280, 25.5sec SuperPI and 32.5K 3DMaark2001.