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From: dfields@neutrino.urbana.mcd.mot.com (David Fields)
Newsgroups: comp.arch
Subject: Re: Interrupts in user space
Message-ID: <1391@urbana.mcd.mot.com>
Date: 20 Sep 90 13:59:02 GMT
References: <MOSS.90Sep17084423@ibis.cs.umass.edu> <12738@encore.Encore.COM> <1990Sep18.152339.25203@tera.com> <3793@goanna.cs.rmit.oz.au>
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In article <3793@goanna.cs.rmit.oz.au>, ok@goanna.cs.rmit.oz.au (Richard
A. O'Keefe) writes:
|>As far as delay slot filling is concerned, this is exactly like
|>	[ Bcc <handler> | LOAD (curptr), dest ]
|>{that is, both kinds of instruction combined in one}.  Either the
|>instructions in the delay slots can safely be executed anyway, or
|>else you have to be able to annul them.  But that's true of any
|>conditional branch.  How complex is this condition?  Well, the 88k
|>does "if R1 = R2 then goto L" as one conditional branch, and that's
|>all we need here.  So
|>

Just to set the recored straight, the 88k does not have such an instruction.
There is a conditional branch which tests for eq0,ne0,gt0,ge0,lt0 and le0
but if you want to test equality of two registers it's a two instruction
sequence.

Others have pointed out the tricks required to resume after an exception
on the 88100.
                                                        
Dave Fields // Motorola MCD // uiucuxc!udc!dfields //
dfields@urbana.mcd.mot.com