Sil3512 can be. If their rom is stored on a flashable chip. I have a really cheap possibly shady one from a bargain bin in Japan with very few markings on it and it does not flash but the "store brand" one I got from NCIX worked just fine. I am betting the house brand Newegg ones would work too. *shrug*

There might be potential for Sil3112 cards but I have never looked into it much so YMMV.

The Sil3512 is not really the greatest chipset and my card does not support hotswap it seems but I still like it more than the onboard PATA in my G4. Not like G4s can reasonably push all that much data anyway. :-/

Here is my original post about the solution I went with for SATA in my G4:

http://forums.applecentral.com/ubbthreads.php/topics/477040/Flashed_Sil3512_info