Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!husc6!wjh12!djb
From: djb@wjh12.harvard.edu (David J. Birnbaum)
Newsgroups: comp.sys.ibm.pc
Subject: Phoenix BIOS 3.07 (5/27/87) for 80286
Message-ID: <398@wjh12.harvard.edu>
Date: 12 Sep 89 14:03:42 GMT
Reply-To: djb@wjh12.UUCP (David J. Birnbaum)
Distribution: na
Organization: Harvard University, Cambridge MA
Lines: 29

While snooping around in high RAM I noticed a peculiarity.  My CompuAdd
286 has a Phoenix ROM BIOS, version 3.07, dated 5/27/87.  Doing a debug
dump of f000:8000 shows that the BIOS begins at this address (at least
the display begins with PPhhooeenniixx, etc.).  But dumping e000:8000
(note: different segment) shows the identical information.  In fact,
dumping several random addresses between e000:8000 and e000:ffff produced
exactly the same display as dumping the same offsets in the f000 segment.
  I called CompuAdd to ask why there should be two apparently identical
copies of the BIOS in high RAM.  I used debug to go to the cold boot
address in the e000 segment and the machine indeed booted, so it looks
like the BIOS is really there.  The CompuAdd technical support folks
mentioned that Phoenix version 3.1 is larger than usual and does extend
into the e000 segment, but the 3.07 shouldn't.  They guessed that my 
BIOS might have been supplied on larger than usual chips, so that the
small amount of information, instead of being confined to addresses
above f8000, is written twice, with the copy beginning at e8000.  I
know virtually nothing about such matters; is this possible? probable?
  In any case, I'd be grateful if:
1) anyone with a 286 with Phoenix BIOS version 3.07 dated 5/27/87 could
peek at high memory and let me know whether they find the same information
and
2) someone could explain what purpose is served by having two identical
copies of the BIOS information.  Is there any way I can reclaim my e000
segment?
  Please reply by email to:
djb@wjh12.harvard.edu [Internet]
djb@harvunxw.bitnet [Bitnet]
  Thanks.
--David