I want to read large blocks from disk to ram, and do calculations
in parallel and I have noticed that reading uses much cpu.
To free up the cpu I try to enable dma with the command:
hdparm -d 1 /dev/hdb
but I get:
HDIO_SET_DMA failed: Operation not permitted
What might be wrong?
According to the manual my motherboard should support dma.
What do I have to do to get DMA working?
Should I try disconnecting most devices except /dev/hdb?
Now I run Linux debian 2.1.54 #10 i586
My system has:
SiS 85C501/502/503 Chipset
PCI QD8580 IDE on board
NCR53c810 (according to kernel. I think that is correct)
/dev/hda is SAMSUNG SHD-3212A (APOLLO-4) AD
/dev/hdb is QUANTUM FIREBALL1080A
/dev/hdc is FX001DE
hda&hdb has DMA according to hdparm -i but hdc is lacking it.
hdc is a 4X CD-rom reader.
There is no occurance of 8580 in /var/log/messages