em man hdparm tu encontras:
-E Set cdrom speed. This is NOT necessary for regular operation, as
the drive
will automatically switch speeds on its own. But if you want to
play with it,
just supply a speed number after the option, usually a number
like 2 or 4.
isso significa que a velocidade do cdrom ou dvd 'e controlada pelo driver do
cdrom.
Se voce tem o driver correto e as opcoes do Kernel
CONFIG_BLK_DEV_IDEDMA_PCI=y
CONFIG_BLK_DEV_IDEDMA_FORCED=y
CONFIG_IDEDMA_PCI_AUTO=y
CONFIG_IDEDMA_ONLYDISK=y
CONFIG_BLK_DEV_ADMA=y
estao ativas entao tu tens teu CDROM &| teu DVD vao funcionar com DMA
se esta opcao estiver ativa :
CONFIG_IDEDMA_ONLYDISK is not set
tu vais ter DMA somente nos HDs.
espero ter ajudado
Marlon
