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Path: sserve!newshost.anu.edu.au!munnari.oz.au!news.Hawaii.Edu!ames!agate!howland.reston.ans.net!pipex!sunic!isgate!veda.is!adam From: adam@veda.is (Adam David) Newsgroups: comp.os.386bsd.questions Subject: Re: 386BSD / NetBSD / FreeBSD Message-ID: <CE5tu9.Eo5@veda.is> Date: 30 Sep 93 09:17:54 GMT References: <1993Sep28.050914.3374@cs.sfu.ca> <1993Sep29.182618.11087@news.csuohio.edu> <1993Sep29.155751.2394@resonex.com> Organization: Veda Systems, Iceland Lines: 21 michael@resonex.com (Michael Bryan) writes: >In article <1993Sep29.182618.11087@news.csuohio.edu> stever@csuohio.edu (Steve Ratliff) writes: >>I would also suggest that you only use 16Mb of mem to start with as >>greater than that is still problematical with non EISA systems. >Just why is this so? I've heard it before, and I know I've even read >an explanation, but I don't remember it anymore. In what way is it >a problem with the current free flavors of BSD? Bounce buffers are not yet implemented in the SCSI system, and there may be other device drivers using busmaster DMA which have a similar problem. The ISA bus cards cannot address higher than the first 16MB, because there are not enough address lines. This is not a problem with EISA cards on an EISA bus, but continues to be a problem if ISA cards (or EISA cards configured for ISA compatibility) are used in an EISA system. Bounce buffers are implemented in the kernel for generic ISA bus access, but only the floppy driver is using this feature so far. -- adam@veda.is