what hardware would these XOR gates need to be added to? The ATA/SATA chipset?
Anyway, I found a review of the Promise S150 SX4 RAID-5 card, the reviewer commented that the card "relies on the server CPU to operate"
Link
My main purpose for this RAID volume is capturing DV video, and then later encoding it to MPEG2. While the capturing phase is hard disk intensive, I don't believe it would need much CPU power. Whereas the MPEG2 encoding uses the CPU and the hard disk transfer demands are I believe minimal. Does anyone think that using software RAID-5 (or even a entry-level RAID card like the Promise or Highpoint) will impact either of these tasks noticeably?