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Newsgroups: comp.os.386bsd.questions Path: sserve!newshost.anu.edu.au!munnari.oz.au!network.ucsd.edu!swrinde!elroy.jpl.nasa.gov!ames!cnn.nas.nasa.gov!wilbur.nas.nasa.gov!tweten From: tweten@wilbur.nas.nasa.gov (Dave Tweten) Subject: Re: local bus video? Message-ID: <CDAxzw.LJ9@nas.nasa.gov> Sender: news@nas.nasa.gov (News Administrator) Nntp-Posting-Host: wilbur.nas.nasa.gov Organization: NAS Systems Division, NASA Ames References: <jstCDApw0.4E8@netcom.com> Date: Mon, 13 Sep 1993 17:02:19 GMT Lines: 37 In article <jstCDApw0.4E8@netcom.com> jst@netcom.com (Jason Thomasser) writes: >Does NetBSD/FreeBSD support local bus video? Local bus is not a software issue. It's a hardware issue. Net/Free/386 BSD can't tell if your graphics card is local bus or not. In general, if your card's register semantics and mapped memory areas are supported by your software, it works, regardless of whether the card is ISA, EISA, VLB or maybe even MCA. >If so will the ATI local bus cards work and are they advisable? The VLB ATI Graphics Ultra Pro works well. I use it. >I guess I may as well ask, why would local bus be an advantage? You want it for graphics update speed, particularly for "frame buffer" style cards like those based upon the ET-4000 chip. Processors do lots of "peeks and pokes" on these cards. Both EISA and ISA are 8 MHz busses (EISA is just twice as wide and uses half the bus cycles to block-transfer data). If you're trying to write a byte into a frame buffer (repeatedly!), they're both 8 megabyte per second busses, divided by the number of ticks to deliver a byte. VLB for a 33 MHz 486DX motherboard is a 33 megabyte per second bus, again, divided by the number of ticks to deliver a byte. With no wait states on the VESA local bus, you can get about a factor of 10 improvement in "peek and poke" performance over either EISA or ISA. The advantage is less pronounced for graphics coprocessor cards (like the ATI GUP and the S3-based cards) because the required traffic between your CPU and the card is reduced. Performance becomes much more a function of the graphics coprocessor's speed and the video memory's speed. -- --------------------------------------------------------------------------- Dave Tweten tweten@nas.nasa.gov NASA Ames Research Center, M/S 258-5 (415) 604-4416 Moffett Field, CA 94035-1000 FAX: (415) 604-4377