SCOUG-HELP Mailing List Archives

<< Previous Message << >> Next Message >>

Date:	Wed, 1 Dec 2004 09:06:07 PST8
From:	Steve Carter <scarter@vcnet.com >
Reply-To:	scoug-help@scoug.com
To:	scoug-help@scoug.com
Subject:	SCOUG-Help: Cause of CD burning failure

Content Type: text/plain

=====================================================
If you are responding to someone asking for help who
may not be a member of this list, be sure to use the
REPLY TO ALL feature of your email program.
=====================================================

JR:

Transfer rates for CD writing are astonishingly slow.

8x is only 8x 150Kbs = 1.2Mbs. Old, slow SCSI (would
be SCSI I (one) if it had been named at the time) is
adequate neglecting overhead. 'Course you've got two
devices which share the same bandwidth. Still, the
transfer rate should not be at issue.

Trouble with reading or transferring usually requires
retries, which slows down the effective transfer rate.
A large buffer (cache) is helpful or even necessary to
overcome this. Sometimes it may become necessary to
make an image of the source disk on the HD in order
to get a good copy, or to copy at higher speeds.

Like any high-speed bus, SCSI is very sensitive to cabling
and termination problems. Re-seating the connectors may
help reduce the effects of poor contact occurring over
time. And a short SCSI bus is a fast SCSI bus. External
cables invariably slow down the bus. Many SCSI users
reserve an entirely separate SCSI bus (at least electrically)
for the external/slow connection. Dual channel SCSI
controllers have become popular for this application.

Just some thoughts.....

-- Steve

And lasers used in readers and writers DO have a finite lifetime,
but it's usually specified around 10K hours. Early HP CD burners
(made by Phillips) were plagued by short laser life. You had to
let them cool down after a burn before starting up again, or
you'd fry the laser diode for sure. That problem is seen much
less frequently today.

+++++++++++++++++++++++++
On 11/28/04, J. R. Fox wrote, in part:
>On my all-SCSI desktop system I've recently started getting cd burn
>failures with RSJ, when duplicating CDs with the CopyWizard. This
>usually happens at the 80 % or 90 % complete mark, and the error is
>something to the effect that the cd reader could not read the source
>disk fast enough. This strikes me as a totally bogus error, because
>it never used to happen. I have tried dropping the burn rate from 8x
>down to 4x, for some CDs, in the hope that this would require less of
>the reader. (No problem with the burner, as best I can see.) This
>*may* allow the duplication to finish successfully in some cases;
>often it does not.
>
>My question: should I be thinking that the cd reader or its laser
>is starting to wear out ? Or is this more likely to be a cable or
>controller issue ? I am reasonably certain that the speed setting in
>the 2940U that controls the two cd drives is correct, and in any case
>it has not been changed in a very long time -- but I will take another
>look at it. I suppose this could be back to cable or connector issues
>again . . . .
>
>
>Jordan
>=====================================================
>

=====================================================

To unsubscribe from this list, send an email message
to "steward@scoug.com". In the body of the message,
put the command "unsubscribe scoug-help".

For problems, contact the list owner at
"rollin@scoug.com".

=====================================================

Return to [ 01 | December | 2004 ]

SCOUG, Warp Expo West, and Warpfest are trademarks of the Southern California OS/2 User Group. OS/2, Workplace Shell, and IBM are registered trademarks of International Business Machines Corporation. All other trademarks remain the property of their respective owners.