flowers@apple.UUCP (11/23/86)
In a recent article, Ephraim Vishniac described some problems with the Quantum
280 drive and the SCSI Manager routines. Unfortunately, the Quantum drives
(including the Q250) have timing characteristics which run up against a problem
in the Mac+ SCSI Manager routines. The unreliable operation Ephraim mentioned
is due to the Mac and the SCSI drive getting one byte out of sync with each
other at certain times during a write to the disk. (This may happen whenever
the SCSI drive is a little slow in taking the last byte of sector data.)
This problem does indeed affect both polled and 'blind' writes. The fix is
not substantial, and will be included in the next System file released by
Apple. (Sorry, but I have no information on the date.) One of the soon-to-be-
released Technotes describes this problem (and it lists the other known SCSI
Manager bugs, for those who are interested). This problem has been hidden for
some time, since most drives are pretty fast in taking all the data. I hope
this throws some light on the situation. And thank you, Ephraim, for
pointing out the problem.
Steve Flowers, System Software Group @ Apple Computer
{sorry, you'll have to look at the path}!apple!flowers
"And I stood beneath the stars, waiting for the dawn to come."