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Newsgroups: comp.os.386bsd.bugs Path: sserve!newshost.anu.edu.au!harbinger.cc.monash.edu.au!msuinfo!agate!tfs.com!julian From: julian@tfs.com (Julian Elischer) Subject: Re: aha0: DMA beyond end of ISA Message-ID: <CwGMpy.HGy@tfs.com> Organization: TRW Financial Systems X-Newsreader: TIN [version 1.2 PL2] References: <KSTAILEY.94Sep19183504@leidecker.std.com> Distribution: comp Date: Wed, 21 Sep 1994 03:22:46 GMT Lines: 38 Kenneth Stailey (kstailey@leidecker.std.com) wrote: : I have a 486DX-2/66 with NetBSD 1.0_BETA and a middle-aged AHA 1542A : controller (it seems ok with AHA_NSEG defined as 17). : When I raise the core memory (RAM) from 16MB to 20MB I get: : aha0: DMA beyond end of ISA : error messages. : Why does this happen? Is there anything that will fix this? This is one of the places where FreeBSD has a slight (and probably short-lived) advantage over NetBSD. The ISA card you have only has 24 address bits.. work it out..... 16MB is the maximum it can reach. teh answer is to transfer the data to a bounce buffer and then 'bounce' it to the correct place... FreeBSD has bounce buufers because they are concentrating on PCs. NetBSD is concentrating on a wider audience, and have not put this code in yet, though I'm sure it's probably 'on the way' your main answers are: 1/ remove 4MB 2/ go to FreeBSD 3/ get an EISA/PCI/VESA scsi card. What most serious NetBSD developers have anyhow..(one reason the ISA problem has been relegated to 'sometime soon' rather than "screamingly urgent"). I'm sure if you are happy with NetBSD, the first or third options are the ones for you. in answer to your question.. YOU could always volunteer to impliment the bounce=buffer system (look in FreeBSD for ideas). : Ken julian