Well, yeah.
From my link: "For enhanced performance, the SiI 0680 can be packaged with Silicon Image's robust Medley? ATA Software RAID, which optimizes throughput and data redundancy. Supporting RAID sets of up to four hard disk drives, Medley? enables RAID 0 Striping, RAID 1 Mirroring and RAID 0+1 Mirrored Striping.
It comes complete with drivers for Windows 98, NT 4.0, ME, 2000 and XP, while also being operational with the default ATA drivers from Microsoft. The use of FLASH allows easy upgrades to the SiI 0680 BIOS. The SiI 0680 is packaged as a compact, 144-pin 20x20 mm LQFP (Low-profile Quad Flat Pack). "
I think you have to spend a lot more money to get a hardware implementation. You make a good point; this card may well be slower than the typical Promise/ Highpoint/ AMI chipsets, which I assume are at least partially programmed in firmware.