How to patch your Motherboard's BIOS
The Good I am using ASUS P4G8X-Deluxe motherboard, equipped with Silicon Image's SATA 3112 Chipset.
The latest BIOS-Version ASUS offers for this motherboard is 1007-002 (beta). Contained therein are several binary images; the one for SiI-Chipset being image version 4.2.47 (observe position no. 26 below):

In order to use the SATARAID Management Utility v 1.22, Silicon Image advise you to use at least ROM-Image v 4.2.50
The Bad Searching the internet, one can find many excellent examples of how to incorporate new images into a BIOS-file. Most of them rely on a tool called CBROM. Unfortunately, CBROM is not able to open the BIOS file used for the ASUS P4G8X Motherboard.
After a while I stumbled upon a tool named ACBROM, which eventually originates from ASUS.
(By invoking 'acbrom.exe 1007_002.bin /b' in a command-shell, you get the output printed in the box above)
The Ugly When you have downloaded all the necessary files you need (acbrom, latest Asus & SiI BIOS), you extract them all into one folder. Note, that we only need SiI 4279.bin image (42kB) for the task at hand. As stated in the readme-file, it is intended for motherboard BIOS for OEM use in development
You should be set with this now:

Now, let's start by extracting the SiI Image contained in the 1007_002.bin BIOS file:

Observe, that there are two new files in your directory:

Besides the FILE_BUF.BIN, there is the uncompressed 4247old.bin file of the currently implemented SiI ROM image within the BIOS-file (1007_002.bin).

Now that was easy. But for the SiI-image to be incorporated into the Asus BIOS, we need to get rid of the code inside the 1007_002.bin image altogether:

Confirm your actions. Note that the list of items does not contain ATA any more:

What's left to do is to put the new SiI ROM image inside the Asus BIOS-file:

The ROM image is compressed and stored in the updated 1007_002.bin image.
Confirm this again. Observe the new ATA line at position 27:

That's it.
Now your ready to flash the BIOS-file 1007_002.bin into your P4G8X motherboard.

CBROM v 2.07, v 2.15, v 6.06
ACBROM v 2.08
Silicon Image's Support Website
Asus FTP-Site for P4G8X-Deluxe BIOS
I could not have written this abstract without Logan's Website on How to Mod a Bios and "Borg Number One" on Short-Media Forums
Keep up the good work.