Xenix, Unix, and IDE drive install problems.

[Tom Friel]

Sorry this is so long, but I would like to know if users of IDE drives
have experienced problems with SCO Xenix 2.3.2 and Interactive Unix 2.2.
I will be nice and not mention drive manufacturers.  I'm posting because,
until recently, I had heard of no such field problems with IDE drives and
had posted a note saying everything was hunky-dory.  We saw nothing in
our labs until August; we have been shipping IDE drives for over 14 months.

Following are excerpts from a note by Interactive's European support
group 8-16-90:

"In some cases 2.2 will boot successfully and installation will appear to
proceed without problems.  Unfortunately, on subsequent reboot the error
'srmount panic' is displayed and you cannot proceed.  Furthermore, attempts
to access the IDE disk filesystems will fail; i.e., 'fsck' will not
recognize the disk.

"The problem was tracked to a timing problem whilst selecting and testing
the presence of a drive.  We have added suitable delay loops around these
functions in the code."  ... the note goes on to say that a replacement
BOOT disk is available, and a driver update to the 'athd' driver.

We have a subsequent note 8-23-90 from a drive manufacturer (in the US):

"In some embedded disk drives the busy bit in the status register will go
low before IRQ 14 has been asserted.  This means that reading the status
register when the busy bit has gone low does NOT guarantee the IRQ to be
cleared.  This time delay for asserting IRQ creates problems for drivers
that use both polling and waiting-for-interrupt methods on different
command sets.  In the case of ISC HPDD, the driver will use the polling
method for the SET PARAMETER command.  However, for other commands such
as READ AND WRITE, the driver acknowledges the command completion during
interrupt.

"A problem arises in the following sequence of events.  The driver issues
the SET PARAMETER command and polls until the busy bit has gone low.  But
IRQ 14 has not yet been asserted due to the time delay.  The driver then
starts up a READ command and waits for completion from interrupt.  When
IRQ 14 is finally asserted for the SET PARAMETER command, the driver will
mis-interpret the interrupt as being for the completion of the READ
command.  The result is that ISC 2.2 cannot be installed on ... IDE drives.

"It is anticipated that the next point release of ISC Unix, tentatively
scheduled for 4th quarter, will fix this problem.  Upgrades will be
available for current ISC Unix customers."

If anyone can provide insights on this whole issue, I would be grateful:
ISC, SCO, drive companies, users, dealers, anyone!

-- 
Tom Friel      | Tandon Computer Corporation           |   (805)  |
tom at quad1.UUCP | 609 Science Drive Moorpark, CA  93021 | 378-7881 |
tom at quad.com   | Moorpark, CA  93021                   |__________|
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