VOGONS


First post, by asdf53

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Socket A systems have a reputation as power hogs, but what about newer motherboards that can manipulate clock speed and voltages? Does it help or will the CPU fail to work at the slightest undervolt? I connected an ampere meter to the PSU to measure total power consumption of the system and did some testing.

System: MSI K7N2 Delta-L (nForce2), Athlon XP 2700+ (Thoroughbred), Geforce 2 MX, 400W IT-Power PSU

I started with a clock speed of 1950 MHz and gradually decreased the core voltage to see how it impacts the power consumption. For testing I used prime95 to get the CPU to 100% load.

1950 MHz @ 1.65v: 132w load / 94w idle
1950 MHz @ 1.6v: 124w / 89w
1950 MHz @ 1.55v: 119w / 85w
1950 MHz @ 1.50v: 116w / 83w
1950 MHz @ 1.42v: 107w / 79w
1950 MHz @ 1.3v: fails to POST

Now for the most interesting part: What is the lowest power consumption we can achieve? I set the clock speed and core voltage to the lowest values that the board supports:

700 MHz @ 1.3v: 70w / 61w

Then I tried to find the sweet spot, the highest clock speed that's still stable at the lowest voltage of 1.3v:

1750 MHz @ 1.3v: 86w / 63w

That's 200 MHz slower than my usual system, but draws 46w / 31w less power. That's pretty good! What are some of your results? Does anyone have a board that can go lower than 1.3v?

Last edited by asdf53 on 2022-10-16, 16:13. Edited 1 time in total.

Reply 1 of 4, by mkarcher

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To get the idle consumption down, research for tools enabling the stop-grant mode of the CPU/chipset, and check whether they work on your board. Possibly you can even find an option to enable stop-grant mode operation (allows the processor to disconnect the FSB and put itself into a static low-power sleep mode) in your CMOS setup. On a cursory research, s2kctl seems to be a tool supporting the nForce2, but nForce2 boards often have problems properly working with the stop-grant mode, but it's worth a try.

Reply 2 of 4, by asdf53

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mkarcher wrote on 2022-10-16, 14:21:

To get the idle consumption down, research for tools enabling the stop-grant mode of the CPU/chipset, and check whether they work on your board. Possibly you can even find an option to enable stop-grant mode operation (allows the processor to disconnect the FSB and put itself into a static low-power sleep mode) in your CMOS setup. On a cursory research, s2kctl seems to be a tool supporting the nForce2, but nForce2 boards often have problems properly working with the stop-grant mode, but it's worth a try.

Thanks, I didn't know about this. I have Windows 98 installed so I cannot test it right now, the patch only works with Windows XP. I will install it later and report back!

Reply 3 of 4, by asdf53

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Wait, s2kctl does work under Windows 98! I had to use a slightly older version. After enabling the halt state and clicking apply, idle consumption dropped from 79w to 60w. That's so cool. How is this so little known?

Here's a link to the author's website of s2kctl: https://web.archive.org/web/20070104164612/ht … targaz0r.nm.ru/
And the version that I used is "s2kctl14b72.zip". Other versions crashed on startup.

I have now installed a Geforce 7600 GT and CPU is at 1800 MHz. Idle: 59w, gaming: 83w. The CPU fan is barely spinning in idle mode. That's really impressive for a powerful Socket A system.

Reply 4 of 4, by mkarcher

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Be aware for side effects, though. On my ECS K7S5A (yeah, I know, not the most highly regarded Socket A board, even though it has its cool black PCB), the hard drive performance on an otherwise idle system dropped from like 50MB/s to 5MB/s on enabling stop-grant mode. Probably because the south bridge needed to wake up the CPU for every couple of bytes read from the hard drive. If you don't notice any problems, though, keeping stop-grant mode enabled doesn't hurt your system.

Actually, it was quite well-known (at least in Germany) back in the days, tools like VCool for VIA chipsets were oftentimes used by PC enthusiasts in the early 2000 years to lower idle power and noise.