thanks for pointing out my misunderstanding. if dma is enabled, why does my nForce4 chipset get such bad SATA performance? "dd -if /dev/sdF0/data -count n" maxes out at ~3MB/sec.
this is the drive configuration: ladd# cat /dev/sdE0/ctl inquiry WDC WD2500JS-00MHB0 config 427A capabilities 2F00 dma 00550040 dmactl 00000000 rwm 16 rwmctl 0 lba48always off geometry 488395055 512 16383 16 63 [etc.] - erik
