Hi,
Can anyone tell me how to get a half decent data rate from a new Plextor
UltraPlex 40max (Model PX-40TSi) SCSI CD-ROM drive. This has an ultra scsi
(Fast-20) interface which, if I read the docs correctly, should be capable
of up to 20Mb/sec.
The drive is suposedly 17x min 40x max. At 40x this should be about
6Mb/sec. Its rotational speed of 8590 RPM (faster than my Barracuda!)
would suggest this is at least possible. Even 17x (2.6Mb/sec) would be nice.
The drive is on a SCSI bus with an HP T4000s tape drive and a Plextor
PX-R412Ci CD-Recorder. The three devices are driven by a Buslogic
(Mylex) BT-930 Flashpoint PCI Ultra-scsi host adapator. The chain is terminated
at the adaptor and at the tape. All three devices are recognised by the BT-930
at boot. It reports
Target 0: Queue Depth 3, Synchronous at 10.0 MB/sec, offset 8
Target 1: Queue Depth 3, Synchronous at 20.0 MB/sec, offset 15
Target 4: Queue Depth 3, Asynchronous
for CD-R, CD, and tape, respectively.
The machine is a P200 with 64Mb RAM running Linux 2.0.35 with the 2.0.14
Buslogic scsi driver. The driver controls this 'narrow' BT-930 and a 'wide'
Multimaster BT-958 for hard discs. (The driver is a joy to setup, BTW).
Depending on how I measure it, I get only about 300-400k/sec. A "block read"
(time -p dd if=/dev/scd1 of=/dev/null bs=1k count=15000) gives:
15000+0 records in
15000+0 records out
real 35.33
user 0.03
sys 0.53
15,360,000 bytes / 35.33 secs = 412.88 kb/sec which is about 2.75x as fast as
a single speed CD. Using 'mkisofs' (a seek intensive test) I get
a similar rate (384kb/sec).
When I first installed the drive it was controlled by a very elderly Adaptec
ava1515 ISA scsi card (using the aha152x driver). This card, with synchronous
transfers disabled, gave similar lousy data rates. I had hoped that the
Buslogic card would spice things up a bit - or even a lot.
This low speed is particularly odd as the Plextor CD-R (a "12x" read non-ultra
scsi-2 device) gives just over 1Mb/sec doing a 15Mb 'dd' and about 370kb/sec
doing 'mkisofs'.
A Hitachi 8x IDE CD drive in the same machine gives 428kb/sec doing 'mkisofs'
and about 1.2Mb/sec doing 'dd'. This latter is about right if you believe
the Hitachi 8x speed claims.
I know that this is a rather simplistic measurement technique, and I don't want
to get into "which is better - scsi or IDE" but I can't help thinking I'm
missing something here. Can this new all singing & dancing ultra
scsi 40x drive really be only a 3x when it comes down to it? What do other
Plextor CD drive users find? Although the 40x drive is new, Plextor have been
selling 20x and 32x drives for a while. Are these just as slow? Why is the
"12x" Plextor CD-R only reading at between 3x and 7x?
I've been surfing around for something to tell the Plextor drives "Hey! Wake
up. Transfer at max speed from now on!" but I have had no luck. The nearest
I got was 'setcd-1.1' by David van Leeuwen but this doesn't seem to work
with any of my CD drives (Plextor or Hitachi) using the 2.0.xx kernel.
I remember somehwere seeing someone do
echo "blah blah" > /proc/scsi/<driver>/<n>
to send commands direct to the adaptor(?). Might this work with correctly
formulated "blah = go really fast"? Can anyone point me to where this is
documented?
Thanks very much for any help and/or comments.
Regards,
Martin Munt
<[EMAIL PROTECTED]> or <[EMAIL PROTECTED]>
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