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From: daemon@decwrl.UUCP
Newsgroups: net.micro.cbm
Subject: ROM-antics
Message-ID: <5532@decwrl.UUCP>
Date: Thu, 9-Feb-84 04:28:12 EST
Article-I.D.: decwrl.5532
Posted: Thu Feb  9 04:28:12 1984
Date-Received: Sat, 11-Feb-84 04:14:18 EST
Sender: daemon@decwrl.UUCP
Organization: DEC Western Research Lab, Los Altos, CA
Lines: 25

From: vogon::goodenough  (Jeff Goodenough, IPG)
In reply to sytek!blk (aka B<), Ray Miller probably did just what I did -
wrote a disassembler and disassembled the ROM.  From then on it's just a
detective game - following leads like the pointer table in low ROM
(near A000) which is in order of token values, and picking out likely
looking bits of code that play with the FAC.  Then you try it out and see
if it works.  As we English say, "the proof of the pudding is in the eating".

Or maybe you *do* have inside info, Ray?  Also, any response on my earlier
comment regarding variable storage?  Another point: could you check that
floating subtract?  My reading of it is that it is an *inverse* subtract
(like divide), so that F1 := F2-F1, not F1-F2.  But I call FSUB at $B850
(instead of B853) which loads the SF variable into F2 first.  Maybe it
moves things around as well, but I don't have my ROM listing with me to
check.

Jeff Goodenough
DEC, Basingstoke, (olde) Hampshire, UK.

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