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So I was booting up my box and for some odd reason my BIOS had lost settings (again), thus resetting everything to defaults. I was digging around making sure things were configured to my liking and noticed the option to enable ACPI 2.0 support. It was disabled by default but I was wondering: Do I need ACPI 2.0 support?

Motherboard is ASUS M3A79-T Deluxe.

EDIT: Updated to the newest BIOS version 1702 without any noticeable changes.

I should also note that I primarily use Windows-7 64-bit.

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ACPI is required for power management to reduce electricity usage and wear-and-tear on the system components. Your motherboard supports the 2.0 revision of the ACPI standard which of course has some enhancements over the original spec, for supported hardware (that board is, but your other devices like CPU, monitor and hard-drive may or may not be—but probably are). The major changes were the addition of 64-bit addressing and device state and multiprocessor support.

So your options are to have power-management or not, and since you can always simply not use it (turn off the options in the power control panel applet), you may as well enable it in the BIOS.



The only reason to disable it is if it is a buggy implementation which ends up causing problems, but neither the motherboard’s manual nor its forums mention any ACPI related issues. The FAQs for it do include one question about ACPI, but that is a specific Vista related issue which is not even an actual problem, just a notice. Therefore, defaulting to disabled is just a curiosity which if really wanted, can be asked.


If you want to learn specifics about the ACPI spec, you can see the changes in Intel’s Technical Update, or a short, general overview at the ACPI site. For real technical details, you can peruse the full specifications.

ACPI is up to version 4.0 at the moment, but 1.0 performs most of the required functions for most purposes. The useful enhancements of later revisions are support for 64-bit, SATA, and PCI-E, but they also include a lot of stuff that most users probably don’t (currently) have or need like MPS, server, ambient-light sensors, user-detection devices, and USB3.

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According to TechARP, this option does not enable specifically ACPI 2.0 features, but enables or disables ACPI itself! Unless you want to go without all power management features (and even if not, it doesn't hurt to have them available), you probably want to leave that option on.

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That seems mighty odd though, seeing as it was disabled by default? –  glenneroo Jan 29 '11 at 22:22
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Hmmm TechARP says: "If you switch from ACPI to non-ACPI mode, or vice versa, Microsoft Windows will fail to boot. You need to reinstall Microsoft Windows everytime you switch modes." - I just changed it and Windows booted fine. Maybe it's a pre-Win7 thing? –  glenneroo Jan 29 '11 at 22:24
    
That's very possible. I know that Windows 7 is a lot less fussy than XP in some other ways too, which is in turn less fussy than Windows 2000, which didn't even handle changing of IDE/SATA port very well. –  farfromhome Jan 29 '11 at 22:27
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As for being disabled by default, that is extremely odd; it's possible that your particular motherboard's meaning for that option is different than what TechARP claims is the normal meaning. –  farfromhome Jan 29 '11 at 22:32
    
@glenneroo, yes, it was an issue in Windows XP that changing the mode required changing the “Computer” device installed in Device Manager, which would rarely work without issue and usually required re-installation. @farfromhome, not really, the manual indicates that it is exactly what it should be. –  Synetech Mar 15 '11 at 19:51

Windows 7 absolutely requires ACPI 2.0 for power management.

It is quite puzzling that it was off and that turning it on didn't have a big impact. You should put your computer into sleep and check that it can wake up, which is a common ACPI problem on ASUS.

A possible explanation for the puzzle is that your BIOS does not fully support ACPI 2.0. The latest BIOS version for your model is number 1702, dating from 2010/10/22, and is available from here (in the Download tab select "Windows 7").

If you decide to update the BIOS, please use great caution and ensure that you also have the media required to reinstall your current version. A botched BIOS update can brick the computer and will require intervention by a professional.

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Updated BIOS to 1702 last week and didn't notice anything. Will try a sleep and report back! –  glenneroo Mar 10 '11 at 16:33
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Ok I can't sleep with or without ACPI 2.0. My box is a bit hacked: I have 2 PSUs running 10 HDDs. I was unable to find a way to connect the on/off switch to the 2nd PSU so I used a paperclip hack to have it always on. This means that when I sleep, the 1st PSU shuts off thanks to ACPI, but then I have to cut power to the 2nd PSU manually. Apparently this isn't "clean" and when I power up, sleep state is deleted. Hibernate (usually) works though! –  glenneroo Mar 16 '11 at 2:03
    
So your motherboard is working as well as can be expected for a normal rig. A better hardware setup might also take care of the 2nd PSU, but I'm no technician. –  harrymc Mar 16 '11 at 7:01
    
Actually there is an adapter for the case (older CM Stacker) but I somehow lost it (or it wasn't included). I should find out what it's called and go find one ;) –  glenneroo Mar 23 '11 at 5:35

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