DSDT

The Differentiated System Description Table is the main table in the ACPI part of a computer's BIOS.

The Advanced Configuration and Power Interface (ACPI) defines a large number of tables that provide the interface between an ACPI-compliant operating system and system firmware. These allow description of system hardware in a platform-independent manner in ACPI Machine Language (AML).

The problem is that OS X has an incomplete ACPI implementation which supports only a subset of DSDT. Modifying the DSDT allows the user to better support their hardware. For example, fixing Time Machine and the UUID 35 error is possible after modifying the DSDT.

To patch your DSDT, you must either use a new table file that someone else has provided, or extract and modify your own. Then tell your bootloader to use the new DSDT file instead of the BIOS. On a few motherboards it is also possible to replace the BIOS with an updated BIOS with a patched DSDT.

Extracting DSDT from BIOS

One of the simplest ways to extract your DSDT from your BIOS is by using DSDT Editor. Once you have downloaded DSDT Editor, open it and press File --> Extract DSDT. After 2-15 seconds, your DSDT should appear on the screen.

DSDT Patches

Having a patch for your motherboard is essential to create your own DSDT, if you couldn't find one online. A large collection of patches are available here: DSDT motherboard patches Assuming you followed the steps above to extract the DSDT from your BIOS, now we are going to apply the patch. Navigate to Patch --> Open, and choose the patch that you downloaded for your motherboard. Once the patch window pops up, press Apply. After a few seconds, navigate to IASL --> Compile . Once the window pops up, there may be a few errors. If so, press 'Fix Errors.' Once it's finished, you have your DSDT. Navigate to IASL --> Save AML As... , and save it as DSDT.aml .

Weblinks

• ACPI Specifications
• DSDT simple editor V1.4.3 - EvOsx86
• DSDT editor - El Coniglio
• DSDT Auto-Patcher - MaLd0n
• DSDT Patcher, a tool to fix your DSDT - InsanelyMac
• Iaslme Drag/Drop GUI for decompiler iasl - InsanelyMac
• MaciASL Native ACPI Machine Language IDE for OS X - Sourceforge
• Using and Debugging ACPI

Sources for patched DSDTs

• Cartri from Brazil provides "Mac Edition" BIOSes for Gigabite P43/P45 motherboards with a patched DSDT.[1]
• List of DSDT patches for the Asus P5E3 Premium (should work for most ASUS P5* motherboards) [2]