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Documentation on Apple's ACPI implementation?

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I'm very new ACPI, DSDT modification and such, but I am diving right in. I've been pouring over the ACPI spec, and realized that I didn't have any clue why certain things needed to be patched. Fixing buggy DSDTs makes sense, but I've been unable to find out what it is exactly that OS X (or more specifically, Lion) hasn't implemented from the intel ACPI spec. Often I understand WHAT the patch is doing, just not why. For example, I often see patches that give the precision timer (usually labeled HPET) more interrupts. I know it's because it's OS X expects the HPET to have 4 interrupts...but where did that information come from?

It would be a huge help if I could find some documentation on the kind of things OS X expects from ACPI, and any stuff Apple left out of their implementation and won't work. I would like to just look through the code of a device having issues and be able to think, "Oh, it's missing this name OS X is expecting so the kext isn't being loaded" or "it's using a method OS X doesn't have, I need to figure out an alternative" then fix it.

As I write this post though, I have a sinking feeling that this is an internally kept Apple secret and everyone has just been discovering OS X's quirks in regards to ACPI through good old fashioned blood, sweat, and beer.

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I've been looking through those, and it looks like lots of talented people have been just figuring it out by comparing their DSDT to dumped Mac ones, using system logs, and the ioregistry. I guess I was hoping it wasn't that hard, hehe. Well, thanks for the help! This DSDT stuff is really fascinating to me, so maybe in a few months I'll be of some help.

Oh, great work on the DSDT editor + patching system and the kext SystemInfo app. Both have been a tremendous help to me, since I am attempting to hackintosh a laptop that has virtually zero information about doing so online. Thanks!

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