I have a Plextor 24/10/40A CDRW drive that is too slow under Linux (Mandrake 9.1, custom kernel 2.4.21-0.25mdkcustom). K3b says it is only going at 16x, even though I tell K3b to go at 20x.

'hdparm -i /dev/hdc' (mapped to /dev/scd0) gives:
/dev/hdc:
Model=PLEXTOR CD-R PX-W2410A, FwRev=1.04, SerialNo=786199
Config={ Fixed Removeable DTR<=5Mbs DTR>10Mbs nonMagnetic }
RawCHS=0/0/0, TrkSize=0, SectSize=0, ECCbytes=0
BuffType=unknown, BuffSize=0kB, MaxMultSect=0
(maybe): CurCHS=0/0/0, CurSects=0, LBA=yes, LBAsects=0
IORDY=on/off, tPIO={min:180,w/IORDY:120}, tDMA={min:120,rec:120}
PIO modes: pio0 pio1 pio2 pio3 pio4
DMA modes: sdma0 sdma1 sdma2 mdma0 mdma1 mdma2
UDMA modes: udma0 udma1 *udma2
AdvancedPM=no

'hdparm -c /dev/hdc' gives:
/dev/hdc:
IO_support = 0 (default 16-bit)

'hdparm -d /dev/hdc' gives:
/dev/hdc:
using_dma = 1 (on)

On my main hard drive (/dev/hde on an HPT366 chipset, an old ATA-66) I copied /etc/sysconfig/harddisks to /etc/sysconfig/harddiskhde and uncommented "EIDE_32BIT = 3". This is the same as 'hdparm -c3 /dev/hde' which dramatically improved the performance of my hard drive. Will the same work for the CD-ROM? I want to avoid producing coasters (failed CD burns when testing) if I can.

Thanks

PS.
My current setup works fine (many successfull CD burns) except for the speed.

Give it a shot, my advice would be then to hdparm -tT the thing with a disc in there to see what sort of speeds you get before and after enabling 32-bit.

Thanks for the reply.
I will give it a try and post the results from the hdparm test you suggested.

I tried it and this is what I get:

hdparm -tT /dev/hdc
/dev/hdc:
read() failed: Input/output error
Timing buffered disk reads: 0 MB in 0.00 seconds = nan MB/sec
Hmm.. suspicious results: probably not enough free memory for a proper test.

Anyway, my original complaint was invalid. K3b restricted the write speed to 16x. It said that the media was incompatible with 20x, even though 40x speed compatible is written on the disks! I did turn on EIDE_32BIT and K3b behaves as before. It may be wishfull thinking but reading from the disk does seem a bit faster.