more data: - irq21 seems to always carry about half of the number of interrupts atapci1 is carrying. - over large periods, the % busy of ad6 is at 100%, servicing maybe 350 or even 800 requests/sec. I/O speed then is around 3-10 MB/sec. this is with 1.10 and SMP. I'll try compiling a old-ata kernel now. cheers simon