On Thu, 19 Sep 2002 23:42:05 +0100 Steve Fosdick fozzy@pelvoux.demon.co.uk wrote:
....
The most likely of these if probably that the drive capability info says the drive doesn't support DMA so the next thing would be to find out where the IDE driver gets that from, whether it is from the drive itself or from the BIOS.
Further to my last message, I have found what appear to be the rules for whether Linux uses DMA automatically (i.e. without hdparm setting it on).
1. If the drive model number is on the bad list then don't use DMA and don't check any further. Drives on this list as of Kernel 2.4.19 are:
WDC AC11000H WDC AC22100H WDC AC32500H WDC AC33100H WDC AC31600H WDC AC32100H WDC AC23200L Compaq CRD-8241B CRD-8400B CRD-8480B CRD-8480C CRD-8482B CRD-84 SanDisk SDP3B SanDisk SDP3B-64 SANYO CD-ROM CRD HITACHI CDR-8 HITACHI CDR-8335 HITACHI CDR-8435 Toshiba CD-ROM XM-6202B CD-532E-A E-IDE CD-ROM CR-840 CD-ROM Drive/F5A RICOH CD-R/RW MP7083A WPI CDD-820 SAMSUNG CD-ROM SC-148C SAMSUNG CD-ROM SC-148F SAMSUNG CD-ROM SC SanDisk SDP3B-64 SAMSUNG CD-ROM SN-124 PLEXTOR CD-R PX-W8432T ATAPI CD-ROM DRIVE 40X MAXIMUM _NEC DV5800A
2. If the BIOS has enabled DMA on the drive then leave it on and set Linux to use it.
3. If the drive is a known good list then turn DMA on. Drives on the good list are:
Micropolis 2112A CONNER CTMA 4000 CONNER CTT8000-A ST34342A
Steve.