Prime95 slowdown after changing motherboards

garo · 2005-06-04, 13:22

I recently posted this on the Ars CPU/mobo forum. But I think the problem is particularly sever with Prime95 - the slowdown with other apps is not as bad. Any ideas?

Quote:

I recently changed the mobo on my Athlon 1.2GHz rig from an Epox 8K7A (VIA KT133) to an ASUS A7V600-X (KT600 chipset). The Epox was going kaput and there was EM interference with my display.

Anyway, I also got myself a stick of DDR400 as the ASUS supports DDR400. I've done all the installs but am very disappointed with the performance. My Prime95 times have dropped from 0.050 sec to 0.093 secs for the exponent I was doing (15.2M range).

I first thought that this may be due to the FSB running at 266(133) and the memory at 400(200). So I went into the BIOS and changed the mem to 266(133). That has made matters even worse and Prime95 time are down (or up) to .189 secs.

Any clues as to what may be going wrong? The machine has a Radeon LE (catalyst thinks it's a 7200), a turtle beach santa cruz, 3COM LAN (in addition to on board LAN), a firewire card and that is about it.

Also, will there be any problem if I up the FSB to 200 and turn down the CPU multiplier to 6 for the same stock 1200Mhz speed for the CPU?

garo · 2005-06-04, 14:57

Whoops! My apologies. The second slowdown (from .09 to .19) was due to prime.ini being corrupted and rewritten resulting in Prime95 prinority going back to 1 from 2. Thus Prime95 had the same priority as dnetc and was thus getting only 50% of the cycles.

And the first slowdown 0.05 to 0.093 was due to carelessness on my part as I was comparing benchmarks of 512K FFT with the 15M exponent which of course is 768K FFT. As the Prime95 benchmark pages show, 0.093 is not a bad time for that FFT.

A couple of further questions remain:

1) What should my RAM timings be (both at 266 and 400 speeds?) I think the current settings (at 266) are 2-3-3-8.

2) Should I bump my FSB to 400 and lower the CPU multiplier or should I leave the FSB at 266 and keep the memory at 400? The CPU is an unlocked Athlon 1.2GHz.

VJS · 2005-06-04, 16:03

Garo,

Running at higher fsb always gave me better performance.

I ran a 1.4G (14x100) socket a at 7.5x200 for quite some time it was alot better at 200 fsb. Just make sure you can keep the cas on the memory low, if not go 166 all around.

garo · 2005-06-04, 17:08

VJS,
Thanks. By SPD the CAS is at 2.5 for both FSB 133 and 200. In fact the SPD settings are: 200MHz, 2.5,3,3,8 wheras it is currently running at: 133MHz, 2.5,3,2,6. My guess is that going to 200 will help the memory. The question is if I can run the processor with 200x6 (or 6.5 if I overclock)? Looking at your post, it seems that I can. I'll try a few combos and report back. Prime95 is currently stable at 0.095sec at 768K FFT (15M).
Garo

outlnder · 2005-06-05, 06:03

The Via KT133 chipset was Via's last decent chipset. Everything after it is junk. If you want a speed up, try the Nvidia chipset.

garo · 2005-06-05, 10:30

Aargh! Too late for that as the place from where I bought it won't do an exchange.

I tried the 6x200 but it doesn't work. It doesn't post and a reboot - thank heavens for Asus C.O.P. tells me that that CPU/FSB combo was invalid. So I'm going with my old 'mildly' overclocked setup of 10x133 with the memory running at 400. I guess I could try tighter memory timings or a higher overclock but I don't have the time to test that the system is stable. Plus running the memory at 266 w/ timings 2.5,3,2,6 vs. 400 w/ 2.5,3,3,8 doesn't seem to make much difference to either Prime95 or the memory bandwidth scores on Sandra. Well, the 40 is just slightly better so I am sticking with it.

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2005-06-04, 14:57	#2
garo Aug 2002 Termonfeckin, IE 2⁴×173 Posts	Whoops! My apologies. The second slowdown (from .09 to .19) was due to prime.ini being corrupted and rewritten resulting in Prime95 prinority going back to 1 from 2. Thus Prime95 had the same priority as dnetc and was thus getting only 50% of the cycles. And the first slowdown 0.05 to 0.093 was due to carelessness on my part as I was comparing benchmarks of 512K FFT with the 15M exponent which of course is 768K FFT. As the Prime95 benchmark pages show, 0.093 is not a bad time for that FFT. A couple of further questions remain: 1) What should my RAM timings be (both at 266 and 400 speeds?) I think the current settings (at 266) are 2-3-3-8. 2) Should I bump my FSB to 400 and lower the CPU multiplier or should I leave the FSB at 266 and keep the memory at 400? The CPU is an unlocked Athlon 1.2GHz.

2005-06-04, 16:03	#3
VJS Dec 2004 299₁₀ Posts	Garo, Running at higher fsb always gave me better performance. I ran a 1.4G (14x100) socket a at 7.5x200 for quite some time it was alot better at 200 fsb. Just make sure you can keep the cas on the memory low, if not go 166 all around.

2005-06-04, 17:08	#4
garo Aug 2002 Termonfeckin, IE AD0₁₆ Posts	VJS, Thanks. By SPD the CAS is at 2.5 for both FSB 133 and 200. In fact the SPD settings are: 200MHz, 2.5,3,3,8 wheras it is currently running at: 133MHz, 2.5,3,2,6. My guess is that going to 200 will help the memory. The question is if I can run the processor with 200x6 (or 6.5 if I overclock)? Looking at your post, it seems that I can. I'll try a few combos and report back. Prime95 is currently stable at 0.095sec at 768K FFT (15M). Garo

2005-06-05, 06:03	#5
outlnder Aug 2002 318₁₀ Posts	The Via KT133 chipset was Via's last decent chipset. Everything after it is junk. If you want a speed up, try the Nvidia chipset.

2005-06-05, 10:30	#6
garo Aug 2002 Termonfeckin, IE 101011010000₂ Posts	Aargh! Too late for that as the place from where I bought it won't do an exchange. I tried the 6x200 but it doesn't work. It doesn't post and a reboot - thank heavens for Asus C.O.P. tells me that that CPU/FSB combo was invalid. So I'm going with my old 'mildly' overclocked setup of 10x133 with the memory running at 400. I guess I could try tighter memory timings or a higher overclock but I don't have the time to test that the system is stable. Plus running the memory at 266 w/ timings 2.5,3,2,6 vs. 400 w/ 2.5,3,3,8 doesn't seem to make much difference to either Prime95 or the memory bandwidth scores on Sandra. Well, the 40 is just slightly better so I am sticking with it.