Newsgroups: comp.arch Path: 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> <1991Apr23.053619.13474@kithrup.COM> <9104231527.AA09611@iecc.cambridge.ma.us> Organization: U of Toronto Zoology 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