Thanks to:
THe KiNG, stickpin, Kabyl, karaakeha1, MadTux, Taruga and everyone (will be listed if I remember) who published kexts and information.

Updated on 2009-11-03 Reorganized

To all Gigabyte AMD w/ALC889A users, it seems to be that my edited kexts could not work on your (AMD) systems. It may be because of AMD chipset. I am really sorry that I could not help you.

Knowledge & How to:
[HOW TO] Patch AppleHDA - Knowledge Base by THe KiNG
How to patch AppleHDA.kext from 10.5.2 and above, Ii is a little bit hard, but is fun. by MadTux
[How To] Pinconfig for Linux users by Master Chief
Audio Device Technologies for Windows from Microsoft
Pin Configuration Guidelines for High Definition Audio Devices from Microsoft
Legacy AppleHDA for BOOT-132 by stickpin
[How TO] 5.1 Surround Sound by consolation
[How to] Have sound on all of your speakers by macgirl

How to get 5.1 audio out of AAC-surround-encoded audio

DSDTs:
DSDT: trick retail drivers by changing "device-id" (e.g USB) by zhell
ACPI (DSDT) Patcher for BIOS and AML by koalala
DSDT Patcher by fassl
DSDT fixes for Gigabyte boards by iSoprano
DSDT - Vanilla Speedstep - Remove _cst errors for MB without C-states by FormerlyKnownAs

Installing a patched AppleHDA.kext, legacy kext, and HDAEnabler.kext to whare?
A vanilla AppleHDA.kext or a patched AppleHDA.kext must be installed into /System/Library/Extensions only.
Any legacy kext(s) and HDAEnabler.kext can be installed into /Extra/Extensions, /Extra/Extensions.mkext, or /System/Library/Extensions.
***If you are using DSDT.aml that has HDEF, you don't need such HDAEnabler.kext.***
***layout-id in DSDT or HDAEnabler.kext must be matched to LayoutID in info.plists of LegacyHDA.kext or AppleHDA.kext.***

Software:
Kext Helper b7 for installing HDAEnabler.kext and AppleHDA.kext to Extensions folder.
Kext Utility for SL



To avoid popping sound (before normal sound) is setting model to be MacPro.

Do not ask me about 5.1 since I have never seen a 5.1 speaker system to be sold at an Apple store, iStudio, in my country.

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About SPDIF output pin on a Gigabyte mainboard
The evening of Nov 16, 2009, I made a coax SPDIF output backet and connected it to SPDIF output pin on board. It worked the same as SPDIF output on the back of mainboard. I tested that the signal passed through a digital receiver, including DTS. I have no idea about audio HDMI since I don't have an LCD/LED TV yet.

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For OS X 10.6 focusing on Gigabyte ALC88#(x), legacy/dummy kexts only.

For using my LegacyHDA.kext with 1.7.9a4 AppleHDA.kext (10.6.2), please remove BuiltInHDA key from info.plist of LegacyHDA.kext., see an example.

by using TextEdit:


or using Property List Editor to remove BuiltInHDA key, see a picture:
 legacyhda.jpg ( 68.12K ) Number of downloads: 1903


Fixing for 10.6.2 by removing BuiltInHDA and including HDAEnabler.kext
 ALC889a_LayoutID_885.zip ( 73.85K ) Number of downloads: 1231



For Gigabyte (E)P35 & (E)P45 and may be compatible to other Gigabyte motherboards on how to make DSDT.
Making DSDT.aml for your PC is better.
There are LegacyHDA.kext for ALC889a and ALC888. 10.5.8 & SL Ready (updated and fixed)
 How_to_patch_DSDT_with_LAN_and_HDEF_functions_including_LegacyHDA.zip ( 552.38K ) Number of downloads: 8954

Also see more info about HDEF @post #392 for ALC889a
Also see more info about HDEF @post #498 for ALC888

Series of LegacyHDA.kext for Gigabyte ALC888 and ALC889a 10.5.8 & SL Ready
Series of LegacyHDA.zip or  Series_of_LegacyHDA.zip ( 414.67K ) Number of downloads: 3023


HDAEnabler for Snow for someone doesn't want to edit DSDT with HDEF.
HDAEnabler for Snow.zip

***LegacyHDA.kext contains only info.plist so it has to work with AppleHDA.kext.***
should be working with vanilla AppleHDA.kext version 1.5.7a24 and higher

Some other Gigabyte ALC88#(x):
ALC662 = ALC662..........found on 945GCM-S2L
ALC883 = ALC883..........found on G31M-ES2L
ALC888B = ALC887 *** found on G41M-ES2L

For testing Gigabyte P55 and P55A users: You may need to update your BIOS. Link to BIOS update
Gigabyte_ALC888b_P55.zip
Gigabyte_ALC889_P55.zip not for ALC889a

For GA-P55A, ALC889: please go to Post #677 by WintonAce for more info and LegacyHDA.kext

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You may use patched AppleHDA.kext of OS X 10.5 to be run on OS X 10.6 at 32bit mode.

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For OS X 10.5 mostly for Gigabyte ALC889a

Before download edited AppleHDA.kext, please read followings:
 readme.pdf ( 17.93K ) Number of downloads: 5202
---> will tell you which kext you want.
 errors.pdf ( 31.29K ) Number of downloads: 1589
---> explains some errors of my previous edited AppleHDA.kexts.
 CodecVerbs.zip ( 4.74K ) Number of downloads: 1938
---> CodecVerbs, 889-00.rtf can be used for Gigabyte ALC889A & ALC888.

Before installing AppleHDA.kext (and HDAEnbler.kext)
If you have ALCInject.kext, AppleAzaliaAudio.kext, or AppleAC97Audio.kext in /S/L/E, please remove it/them.
=========================================================
These followings are edited AppleHDA.kexts for ALC889A. You may choose the one fits to your system.

Requirement: OS X 10.5 or higher
for ALC889A layout-id = 12 ; 0x0000000c ; 0x0c, 0x00, 0x00, 0x00
from 10.5  1.4.0a22.zip ( 409.6K ) Number of downloads: 1589


Requirement: OS X 10.5.4 or higher
for ALC889A layout-id = 889 ; 0x00000379 ; 0x79, 0x03, 0x00, 0x00
 1.5.7a24_3outs3ins_digital_HDA_headphone.zip ( 534.19K ) Number of downloads: 1086

 1.5.7a24_3outs3ins_digital_regular_headphone.zip ( 535.83K ) Number of downloads: 370

 1.5.7a24_4outs3ins_analog_HDA_headphone.zip ( 534.21K ) Number of downloads: 592

 1.5.7a24_4outs3ins_analog_regular_headphone.zip ( 535.45K ) Number of downloads: 386


Requirement: OS X 10.5.6 or higher
for ALC889A layout-id = 889 ; 0x00000379 ; 0x79, 0x03, 0x00, 0x00
 n1_1.6.2a37_3outs3ins_digital_HDA_headphone.zip ( 603.48K ) Number of downloads: 592

 n2_1.6.2a37_3outs3ins_digital_regular_headphone.zip ( 604.48K ) Number of downloads: 300

 n3_1.6.2a37_4outs3ins_analog_HDA_headphone.zip ( 603.21K ) Number of downloads: 613

 n4_1.6.2a37_4outs3ins_analog_regular_headphone.zip ( 604.25K ) Number of downloads: 346


Requirement: OS X 10.5.6 or higher
for ALC889A layout-id = 889 ; 0x00000379 ; 0x79, 0x03, 0x00, 0x00
These following files have no front mic that causes of "Sound assertion "0 == fMikeyDriver" failed in "/SourceCache/AppleHDA/AppleHDA-162.1.37/AppleHDA/AppleHDADriver.cpp" at line 1063 goto handler."
 N1_1.6.2a37_3outs2ins_digital_HDA_headphone.zip ( 603.32K ) Number of downloads: 476

 N2_1.6.2a37_3outs2ins_digital_regular_headphone.zip ( 604.33K ) Number of downloads: 190

 N3_1.6.2a37_4outs2ins_analog_HDA_headphone.zip ( 603.05K ) Number of downloads: 323

 N4_1.6.2a37_4outs2ins_analog_regular_headphone.zip ( 604.09K ) Number of downloads: 245

------------------------------------------------------------------
Credit to stickpin for making legacy kexts.
working with AppleHDA.kext version 1.5.7a24, 1.6.2a37
for ALC889A layout-id = 889 ; 0x00000379 ; 0x79, 0x03, 0x00, 0x00
 Legacy_3outs3ins_digital_HDA_headphone.zip ( 21.74K ) Number of downloads: 662

 Legacy_3outs3ins_digital_regualr_headphone.zip ( 21.96K ) Number of downloads: 281

 Legacy_4outs3ins_analog_HDA_headphone.zip ( 21.67K ) Number of downloads: 493

 Legacy_4outs3ins_analog_regualr_headphone.zip ( 21.91K ) Number of downloads: 332


No front mic available.
 series_of_legacy_no_front_mic.zip ( 95.22K ) Number of downloads: 435


*****************************************
Requirement: OS X 10.5.7 or higher
1.6.8a3 AppleHDA [/color]note: front mic is not available. *** [color="brown"]layout-id = 885 ; 0x00000375 ; 0x75, 0x03, 0x00, 0x00***
 HDAEnabler_for_1057.zip ( 11.88K ) Number of downloads: 1623
This HDAEnabler.kext should be used with 1.6.8a3 AppleHDA.kext.
 L1_3outs2ins_digital_HDA_headphone.zip ( 630.14K ) Number of downloads: 690

 L2_3outs2ins_digital_regular_headphone.zip ( 631.01K ) Number of downloads: 307

 L3_4outs2ins_analog_HDA_headphone.zip ( 629.92K ) Number of downloads: 588

 L4_4outs2ins_analog_regular_headphone.zip ( 630.8K ) Number of downloads: 408

 Series_LegacyHDA_1057.zip ( 109.58K ) Number of downloads: 1132

*****************************************
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vanilla AppleHDA.kext
 Original_AppleHDA.kext_1.5.7a24.zip ( 521.78K ) Number of downloads: 387

 Original_AppleHDA.kext_1.6.2a37.zip ( 641.3K ) Number of downloads: 1009

================================
Previous edited AppleHDA.kexts
1)  ALC889A_V1.zip ( 1.01MB ) Number of downloads: 887

2)  ALC889A_V2.zip ( 1.01MB ) Number of downloads: 1113
removed all "SignalProcessing" key from PathMapRef.
3)  ALC889A_1056.zip ( 746.25K ) Number of downloads: 631

4)  ALC889A_1056_fix.zip ( 747.3K ) Number of downloads: 2450
Front mic fixed.
5)  AppleHDA_10.5.6.zip ( 549.78K ) Number of downloads: 1227

---------------------------------------------------------
AppleHDA.kext for ALC888 (Gigabyte), tested on GA-EP45-UD3LR (gave to my brother)
1.5.7a24 888.zip
1.6.2a37 888.zip
---------------------------------------------------------
DIY
Edit AppleHDA.kext/Contents/Resources/English.lproj/Localizable.strings, see picture below for an example:
 local_strings.jpg ( 265.72K ) Number of downloads: 3020

and results
 local_in.jpg ( 67.4K ) Number of downloads: 2247
 local_out.jpg ( 59.01K ) Number of downloads: 1480

(got from AlainTox714's thread)

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Off the topic: on Nov 25, 2009
Issue: Geforce 7000 series & 10.6.2

Using DSDT w/ GFX or GraphicsEnabler=y for running only 32bit, got GUI KP if trying 64bit.
=============
On EP35-DS3P with DUAL graphic cards

8800GT into PCI-E x16 & 7300GT into PCI-E x4:
set 8800GT first boot, 64bit OK.
set 7300GT first boot, not test yet


7300GT into PCI-E x16 & 8800GT into PCI-E x4:
set 7300GT first boot, only 32bit working, 64bit got GUI KP
set 8800GT first boot, system frozen on 32 & 64bit, spinning stopped