Date   : Mon, 25 Sep 1989 16:31:09 GMT
From   : sumax!amc-gw!sigma!flash!bill@beaver.cs.washington.edu (William Swan)
Subject: Alspa Computer ACI-1/2 users only - BIOS bug

(Has the Alspa mailing list actually expired? I got no answer...)

While checking out Dave Goodenough's CP/M UUCP, I uncovered a bug in the
Alspa ACI-1&2 BIOS that apparently goes all the way back to the early
Alspaugh Engineering days (i.e., it's not *my* fault :-).

As I have been afflicted with various symptoms of this bug over the years,
usually chalking it up to the particular applications I was running, I
figure it worthwhile to share with other Alspa users on the net (and off,
but I know only one in that category).


The symptom, in general, is that an application running from one drive
fails to find all the files on another drive specified by a wildcard. I
have seen this with the above UUCP, with SHAR.COM, and a CP/M make. For
some reason I have not seen this with Alspa's D.COM.


The problem is caused by the BIOS density (disk format) routines use of
the 128-byte scratch directory buffer (DIRBF) as a scratch buffer for
reading track 0, sector 1, to determine the disk format encoded therein
at byte 7FH.

This causes the directory buffer to be clobbered between search-first and
search-next BDOS calls, and any matching but unfound file entries in the
buffer at that time will not be found.


Two fixes are possible. The first is to create a separate 128-byte buffer
for the "density" routines, so that only the BDOS uses DIRBF. The second
is a re-write of the density routines such that it is not necessary to
actually read the data into memory. (The Alspa BIOS is so tight that I
preferred the second.) Rather than list that change here, I will e-mail
the revised BIOS to anybody who requests a copy.

(Note: I have done a *lot* of work on the BIOS - it is at rev 3.7 now, up
from the last ACI v3.0, and accomodates P2DOS and ZCPR3 among other things.)



-- 
Bill Swan  entropy.ms.washington.edu!sigma!bill  Send postal address for info:
       Innocent but in prison in Washington State for 13.5 years:
       Ms. Debbie Runyan: incarcerated 01/1989, scheduled release 07/2002.
                          In now:  0 years,  8 months,  0 weeks,  5 days.