MAMEWorld Forums - The Loony Bin - Re: ACPI - what do you know about it?

> I found this about it in Wiki:
>
> Linus Torvalds, creator of the Linux kernel, once described it as "a complete design
> disaster in every way", in relation to his view that "modern PCs are horrible".
>
> Thoughts, ideas, rantings....?

Why do you ask?

Some manufacturers optimize the ACPI code for Windows only and compile it using Microsoft's ACPI compiler. Then sometimes you have to manually fix and recompile your ACPI tables to get power management properly working on Linux. There are whole forums dedicated to this discipline.

Those who have studied the ACPI specs pdf extensively all say that Hewlett Packard write some of the worst ACPI code in the world.

Some really nerdy stuff you can do if you're curious:

Make sure ACPI 2.0, ACPI APIC and all CPU features (Except CPU ID limit, which is for backwards compatibility with old OS such as Windows 98) are enabled in your motherboard BIOS settings. While you're there, if you're using a 64-bit OS, set the HPET to 64-bit, if you have such a setting.

On Windows, you can dump your ACPI tables with Everest Corporate Edition, and decompile them using IASL: http://www.acpica.org/downloads/binary_tools.php
Try decompiling your DSDT table with IASL, then compile it and see how many errors and warnings you get. I can almost guarantee you it won't be pretty.

You can boot from a Linux Live CD (Mint for example), open a command prompt and type dmesg|grep ACPI to see what's working and what isn't. I haven't played around with this much but I know there are various boot flags that enables and disable ACPI features. Linux Mint for example is set to use a minimal ACPI feature set to avoid compatibility issues. I guess this is probably true for most Linux distros.

If you're using Windows 7 (probably Vista too) start an elevated command prompt, navigate to the root of your drive and type powercfg -energy. an "Energy Report" will be saved to the root of your drive.

When doing this, I get this message, once for each CPU core: "There is a problem with the definition of the ACPI _PSD object on this computer. Installing the latest system firmware (BIOS) may resolve this issue". The PSD code has to do with CPU power state switching and is part of the SSDT ACPI tables.

Download and install the "Windows driver kit" and run pwrtest /info:ppm. This will show all available P- and C-states for your CPU.

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