CD-writing: buffer underruns writing from HD at 8x writing speed with kernel 2.4.18
Hi,
There once was a time I could copy CDs on the fly, or write them from HD
with 12x (as much as my CDRW supports) without a problem.
Months ago it stopped to work at reasonable speeds. I didn't have the
time to investigate it fully then, unfortunately. Now I did, and here's
the result:
The setup:
kernel is 2.4.18 (I use the low latency patch, but I have tested it
without the patch too, same result)
RW-drive is an IDE Philips CDRW 1208 (cdrdao driver generic-mmc-raw)
ROM-drive is a Plextor PCX-40TS (40x) SCSI drive on an Adaptec
controller (PCI, 2140 IIRC).
Everything is setup ok AFAICS, done according to cd-writing-howto
I use a ~3 yrs old 10 gig IDE HD (the same one I used when everything
went OK), set with hdparm to:
sonic:~# hdparm /dev/hda
/dev/hda:
multcount = 16 (on)
I/O support = 3 (32-bit w/sync)
unmaskirq = 0 (off)
using_dma = 1 (on)
keepsettings = 0 (off)
nowerr = 0 (off)
readonly = 0 (off)
readahead = 8 (on)
geometry = 1650/255/63, sectors = 26520480, start = 0
busstate = 1 (on)
sonic:~#
The PC is an AMD K6 450, IDE chipset is ALI M15x3
There are 2, possibly connected, problems:
1) When I read data from HD I can write ok, as long as the speed doesn't
exceed 8x. Otherwise, I get buffer underruns very soon. gtoaster reports
~1500 kB sustended throughput. There is clearly something wrong. The
cdrdao command line is:
cdrdao --simulate --paranoia-mode 3 --speed 8 --device 1,0,0 --driver
generic-mmc-raw:0x0 --buffers 60
2) When copying on-the-fly, I have to use speeds not exceeding 4x. At
4x, the buffer is always full. At 8x, instant underrun. This may be a
flaky source drive, but in conjunction with the above prob I am not
sure.
I'd be glad if someone could give hints, this drives me crazy.
Thanks, M
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