Date   : Thu, 28 Apr 1988 23:17:13 GMT
From   : eve.usc.edu!mlinar@oberon.usc.edu (Mitch Mlinar)
Subject: Help with Xerox 820-1

In article <7998@pur-ee.UUCP> young@pur-ee.UUCP (Mike Young) writes:
>
>   Xerox 820 boards had the WD1771 disk controller. Won't do double
>density. There are those who have managed to hack the board to do DD, but
>it involves a daughter board, doubling the CPU clock, hoping the DRAMs
>can run that fast, etc. etc. Quite a project.

Not quite true.  The Xerox 820 runs at 2.5 MHz which is more than adequate
for 5.25" double-density.  Although it does not quite hack it for a *generic*
8" DD disk driver, the SWP package I mentioned earlier supports 8" DSDD at
2.5 MHz by clever programming.  The SWP package requires absolutely *no*
modifications to the Xerox 820-I - although I do recommend a modification to
increase delay for the head settling time (after seek).  This allows a high
step rate; I run all my 8" drives at 3 mS on the -I.

-Mitch