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In some computers, when I put them to stand-by, they do not shut down their fan-based coolers. Even though they go stand-by (and can be waken up with the mouse), they just don't shut up.

I have no idea if the CPU is still consuming power, but it's cooler is, and also the case fan.

I'm sure the PC is in stand-by because a decorative light in its front blinks, which makes me believe the motherboard understands what stand-by means. Also, the CPU's fan in wired into the mobo, not directly to the power source. The network card shuts off (the LED goes off) and the hard disk spins down, but the fans are still on.

It's an old ASUS A7V8X-X with AMD Athlon XP 2000+, but it also happens to another, old, ASUS A7N266-VM with AMD Athlon XP 2200 (update: In which case it may be expected, as only the case fans, connected directly to the power supply, keep running). And it also happens to somebody else's PC with unknown specs, so it's not that my PCs hate me. I guess. Dunno.

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Hmm, section 1.3 on page 3 of the manual for the A7N266-VM specifically states “Auto Fan Off: The system fans power off automatically even in sleep mode.” There does not seem to be a fan-speed control option in the BIOS (eg Smart Fan, Q-Fan, etc.) so it is strange that board is experiencing this.

The manual for the A7V8X-X barely mentions fans at all, so it should presumably behave like standard motherboards.

Are you using a fan-speed monitoring/controlling (software) program? Perhaps it is overriding the automatic shutdown.

Have you tried connecting the fans to a different fan header?

I had this happen with a motherboard last year. To fix it, I had to change the standby mode from S1 to S3. Since the BIOSes for your boards do not seem to have an option to specify the standby mode, you should be able to set it in Windows with the dumppo tool. (Other people have experienced this.)

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Hey, thank you very very much for such a high-quality reply, you're awesome (I didn't have the manuals, thanks for the links). I'm not using any fan-related software, the XP SP3 install on the A7V8X-X is relatively fresh, and updated. The A7N266-VM one actually runs Linux Mint Debian, fresh install this week. I did not ever install Windows on it, so I don't know if it would have a different behavior (should I image the partitions, install windows, check if it still happens, restore?) Oh, the latter has the case fan directly on the power supply. – Camilo Martin Feb 12 '12 at 9:27
Ok, I regret not checking it twice before - as you said, the CPU fan of the A7N266-VM does go off in standby (but not the case fan, which is connected to the power supply through one of those yellow-black-black-red connectors) - I do not know if there is hope for it to go off, or if I can connect its wires somewhere else (would I damage something if I made a parallel connection with the CPU's fan cables, which do go off properly? I have a rudimentary understanding of electronics). – Camilo Martin Feb 12 '12 at 10:00
You can easily get a Molex-to-fan adapter. You can find them on eBay for as little as $1 with free shipping or at your local computer shop. But first, did you try changing the suspend mode with the dumppo utility on the Windows one? – Synetech Feb 12 '12 at 17:43
I did not explain myself well - the case fan is connected to a molex with an adapter like this one (with a female and a male like in the picture). But it still does not power off in standby (while the CPU fan does). Regarding the A7V8X-X one, I used the dumppo utility, and set it to a minimum of S3, and in the BIOS I've set "ACPI suspend to RAM" (under "Power") to "enabled". Results are most weird. Now if I go stand-by, the fans go off, and the stand-by indicator blinks as it should, but I can't wake it up. (continues) – Camilo Martin Feb 15 '12 at 1:06
If it has a Molex connector, then the system cannot control it like it can with a fan connector (ie turning off just the fans), it can only cut the power to all Molex connectors by going into standby. Re Power-up control; those options are for turning the system on, not resuming from standby. You need to set the jumper called KBPWR to enable activating with a PS/2 keyboard and the USBPWR jumpers to activate with a USB mouse/keyboard. Check pages 20-21 in the manual for instructions and location photos on pages 5 & 8. – Synetech Feb 15 '12 at 1:21

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