Date: Sun, 1 Nov 1998 10:44:00 +1030 From: Greg Lehey <grog@lemis.com> To: John Polstra <jdp@polstra.com>, hardware@FreeBSD.ORG Subject: Re: Mixing 8- and 16-bit shared memory ISA cards Message-ID: <19981101104400.A28493@freebie.lemis.com> In-Reply-To: <199810311853.KAA22693@austin.polstra.com>; from John Polstra on Sat, Oct 31, 1998 at 10:53:15AM -0800 References: <199810311853.KAA22693@austin.polstra.com>
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On Saturday, 31 October 1998 at 10:53:15 -0800, John Polstra wrote: > I have a question for you old farts who still remember ISA. That's starting to date us, is it? > I'm trying to turn an old 486 box into an ethernet <-> frame relay > router. It has a 16-bit SMC 8013 card with shared memory, and also > an 8-bit ET Inc. card with shared memory. I have this vague > recollection that you can run into problems with a mix like that in > an ISA machine. In particular, I seem to recall something along the > lines that each 128K chunk of the address space (a0000-bffff, > c0000-dffff, e0000-fffff) has to do either all 8-bit accesses or all > 16-bit accesses, but not a mix of the two. Yes, there was something like that, and I think you've remembered it pretty well. > Is that correct? Is it true for FreeBSD systems, or was it just an > MS-DOS thing? Is such a mix guaranteed not to work, or does it just > sometimes not work? IIRC (and that's not sure), it was a hardware limitation with 286 (and maybe 386) machines. It's quite conceivable that it doesn't apply to more modern machines. > Also, is the address chunk e0000-effff generally available on ISA > 486 systems (non-IBM)? I know it used to be reserved for the Basic > ROM on ancient IBM machines. I think you'll have to check that for yourself. Many motherboards mirrored the system BIOS there. > Finally, what about the range a0000-bffff that is generally used by > video cards? The docs for my card (an old 1 MB Orchid ProDesigner > ISA card) say that it uses that whole range. But I am only using it > in text mode with the syscons driver. Will it still take up that > whole address range in that case, or will part of the address space > be free for other cards? No, it only takes up some of it. I forget which half; again, read and see. Greg -- See complete headers for address, home page and phone numbers finger grog@lemis.com for PGP public key To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hardware" in the body of the message
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