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From: phorgan@cup.portal.com (Patrick John Horgan)
Newsgroups: comp.sys.amiga.tech
Subject: 2090a direct SCSI
Message-ID: <27494@cup.portal.com>
Date: 3 Mar 90 08:30:34 GMT
References: <10910@june.cs.washington.edu>
Organization: The Portal System (TM)
Lines: 13

A friend of mine who's hacking a tape backup disassembled the driver
for the 2090a and found out why the dern thing won't do direct
SCSI writes.  It seems that the high order bit of one of the DMA
registers specifies read or write, and the code never pulls up the
put for write.  He also found a workaround.  He set bit 24 (the 
25th bit counting 0), of the data buffer address.  Only 24 bits
are used (0-23), but the higher bits aren't checked or cleared.
This bit position luckily gets slid in to the high bit of the
DMA register causing write to work:)  He told me the day before
yesterday that he's been able to write to a SCSI tape drive with
the 2090a, and hopes to have a driver written soon.

Patrick Horgan                           phorgan@cup.portal.com