https://qa.mandrakesoft.com/show_bug.cgi?id=477
------- Additional Comments From [EMAIL PROTECTED] 2003-01-22 01:40 -------
This bug appeared because of the following lines in /etc/rc.sysinit (on mandrake-9.0).
997 # Turn off DMA on CD-ROMs. It more often than not causes problems. 998 if
[ -x /sbin/hdparm -a -e /proc/ide ]; then 999 for N in `grep -v ide-disk
/proc/ide/*/*/driver 2>/dev/null | awk -F / '{ print $5 }'`; do 1000
hdparm -q -d0 /dev/$N >/dev/null 2>&1 1001 done 1002 fi In other words, if
hdparm is installed, the script turns off DMA on CD/DVD drives. This means its not a
kernel bug. In fact, it is hardly a real bug since its intentional. The "mandrake"
reason being "It more often than not causes problems". If this script is fixed, the
bug will go away.
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description:
"dmesg | grep DMA" shows:
hdd: DMA disabled
I have the ECS k7vma motherboard (VIA 686B southbridge). /dev/hdd is a DVD
drive. Since the kernel disables the DMA on the DVD drive, playing DVD is hard
because of high framedrops (even with AGP 4x mode enabled on my nvidia card).
System load goes up to 1.5. Once I enabled DMA on /dev/hdd (using hdparm), DVD
playback became smooth with system load falling below 0.5 !!
Why does the kernel disable DMA in CD/DVD drives, when the same kernel
enables (by default) UDMA5 modes on my hard drive ? Makes little sense.
