Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!csd4.milw.wisc.edu!uxc!uxc.cso.uiuc.edu!mcdurb!aglew
From: aglew@mcdurb.Urbana.Gould.COM
Newsgroups: comp.arch
Subject: Re: 68000 architecture
Message-ID: <28200334@mcdurb>
Date: 11 Jun 89 19:28:00 GMT
References: <65416@<1989Jun4>
Lines: 19
Nf-ID: #R:<1989Jun4:65416:mcdurb:28200334:000:873
Nf-From: mcdurb.Urbana.Gould.COM!aglew    Jun 11 14:28:00 1989


>| 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.
>
>It's useful on occasion. For example, Amiga shared libraries have shared
>data at positive offsets, and a jump table at negative offsets.

The 88K does not have signed offsets (except for branches).

I recall (but do not have the reference handy) a paper by some fellows from
Tektronix who were porting Scheme to the 88K that listed lack of signed 
offsets as one of the things that made their task slightly more difficult.
However, lack of signed offsets certainly has not prevented LISP and other
AI type languages from being ported to the 88K.

Come to think of it, I have several hundred megabytes of 68K opcode traces 
sitting on tape somewhere - let me go and count the number of negative
offsets in them.