Path: utzoo!attcan!utgpu!watmath!iuvax!rutgers!rochester!quiroz
From: quiroz@cs.rochester.edu (Cesar Quiroz)
Newsgroups: comp.arch
Subject: Re: 68000 architecture
Message-ID: <1989Jun8.142409.22589@cs.rochester.edu>
Date: 8 Jun 89 18:24:08 GMT
References: <1989May30.171335.473@utzoo.uucp> <658@geovision.UUCP> <40938@bbn.COM> <660@geovision.UUCP>
Reply-To: quiroz@cs.rochester.edu (Cesar Quiroz)
Organization: U of Rochester, CS Dept, Rochester, NY 14627
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In <660@geovision.UUCP>, gd@geovision.UUCP (Gord Deinstadt) wrote:
| ...
| Actually, I don't mind the absolute addresses being signed; it's a
| fairly minor issue.  It's the signed offsets in base+offset mode that
| burn me up.  You *can* work around it (ie. still get a 64k address
| range with 16-bit offsets) by fudging all your
| base addresses by 32768; but you shouldn't have to.  Especially
| considering that this was in the days when people still wrote
| a lot of assembler.  (Gosh, did people actually do that when
| I was young? ;-P)

You would be surprised...  In a former life I did some System 370
assembly, and one of the most common complaints was that literal
offsets went only forwards (4K?).  A properly twisted mind will pass
you addresses in the middle of some structure and hope you know what
you are doing.  (There may have been also some trouble when writing
macros wherein one would branch to a lower address that you forgot
to label, but I am now blissfully ignorant of the macro assembler,
so this recollection is likely to be bogus.)  So signed vs unsigned
offsets seems to be a judgment call, you will make some people
unhappy either way.  Also, we are talking here offsets of 32K before
you see the difference, probably not such a frequent problem any way.

-- 
                                      Cesar Augusto Quiroz Gonzalez
                                      Department of Computer Science
                                      University of Rochester
                                      Rochester,  NY 14627