Date: Sun, 1 Nov 1998 15:25:39 +1030 From: Greg Lehey <grog@lemis.com> To: dg@root.com Cc: John Polstra <jdp@polstra.com>, hardware@FreeBSD.ORG Subject: Re: Mixing 8- and 16-bit shared memory ISA cards Message-ID: <19981101152539.R28493@freebie.lemis.com> In-Reply-To: <199811010355.TAA01865@implode.root.com>; from David Greenman on Sat, Oct 31, 1998 at 07:55:32PM -0800 References: <19981101104400.A28493@freebie.lemis.com> <199811010355.TAA01865@implode.root.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Saturday, 31 October 1998 at 19:55:32 -0800, David Greenman wrote: >>> 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. > > It affects all machines with ISA busses, not just early x86. What's the reason for it? 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
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?19981101152539.R28493>