Re: Bitfield instructions--a good idea?

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Article #10435

#10435

From: Henry Spencer
Date: Wed, 24 Apr 1991 17:34

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In article <9104231527.AA09611@iecc.cambridge.ma.us> johnl@iecc.cambridge.ma.us (John R. Levine) writes:
>>Anybody who caches a frame buffer is crazy. ...
>
>Given how slow some of the frame buffers on PC clones are, upwards of 10
>wait states per 16 bit word, caching could be a big performance win.

It's only a win if you are reading that word *repeatedly*.  This isn't
too likely to be a major performance issue.  If you are twiddling around
in a small area, odds are good that your performance is dominated by
overhead and not by frame-buffer accesses.  If you're doing something
big, it's probably being done a word at a time without repeated accesses
to the same word, and it's also probably going to bust your cache if
you cache those accesses.
-- 
And the bean-counter replied,           | Henry Spencer @ U of Toronto Zoology
"beans are more important".             |  henry@zoo.toronto.edu  utzoo!henry

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<1991Apr15.193425.3436@waikato.ac.nz> <SPOT.91Apr18123711@WOOZLE.GRAPHICS.CS.CMU.EDU> <PUWA8R4@xds13.ferranti.com> <1991Apr23.053619.13474@kithrup.COM> <9104231527.AA09611@iecc.cambridge.ma.us>

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Newsgroups: comp.arch
Path: arc1-ca.pugleaf.net!utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: Bitfield instructions--a good idea?
Message-ID: <1991Apr24.173400.13397@zoo.toronto.edu>
Date: Wed, 24 Apr 1991 17:34:00 GMT
References: <1991Apr15.193425.3436@waikato.ac.nz> <SPOT.91Apr18123711@WOOZLE.GRAPHICS.CS.CMU.EDU> <PUWA8R4@xds13.ferranti.com> <1991Apr23.053619.13474@kithrup.COM> <9104231527.AA09611@iecc.cambridge.ma.us>
Organization: U of Toronto Zoology

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