Both the Silicon Image configuration utility and Nero report the drive
in PIO4 mode.

Are you sure that the terms "PIO" and "UDMA" apply to non-standard (i.e. not register-compatible with the old PC/AT IDE) SATA controllers?

This very same Silicon Image chip serviced a disk array of 2 disks important to me (Windows Dynamic Disk stripe set) for ~3 years, and I had no issues with it.

I have a hunch it may have something to do with Microsoft.

Doubts. SiL chip is presented as SCSI in Windows, i.e. it does not use MS's ATA stack, and MS are not the driver writers for the SiL chip.

SCSIPORT itself, on which the SiL's driver is based, is surely stable and has no this major perf issues. BTW - SCSIPORT does not what is "PIO" and "UDMA" at all :-)

I'm out of ideas.

Try moving the combination of CD drive+SiL card to another machine. Try connecting this CD to another SATA controller. Try connecting another SATA CD to this SiL chip.

You have some unlucky hardware configuration.

BTW - this SiL chip is known to have PCI issues with nForce north bridge (actually they are nForce's issues, but nevertheless).

I downloaded the WDK and may try to trace the code using a debugger.

Useless without the source which you do not have.

--
Maxim S. Shatskih
Windows DDK MVP

http://www.storagecraft.com