Hi,

I'm using RHEL5 on a SATA HDD on a hp xw4600 workstation with an intel ICH9 chipset. The system BIOS is set to IDE mode rather than AHCI. When RHEL5 boots up, the HDD is recognized as /dev/hda. However, UDMA does not seem to be enabled. When I do a benchmark using hdparm -t /dev/hda, the speed is extremely slow(~3MB/s), and when I try to enable UDMA using hdparm -d1 /dev/hda, I get the following error:
Code:
/dev/hda:
setting using_dma to 1 (on)
HDIO_SET_DMA failed: Operation not permitted
using_dma    =  0 (off)
When I try to find out which kernel module it's using(ahci or ata_piix or something else) using lspci, I don't see the module at all. When I do the same thing on Mandriva 2009, lspci reports using ahci module when system BIOS is set to AHCI, and ata_piix when system BIOS is set to IDE.

I also find it strange that RHEL5 detects the HDD as /dev/hda when system BIOS is set to IDE. However Mandriva 2009 detects it as /dev/sda.