Path: utzoo!attcan!uunet!husc6!cmcl2!nrl-cmf!ames!pasteur!ucbvax!trwind.ind.trw.COM!karl From: karl@trwind.ind.trw.COM (Karl Auerbach) Newsgroups: comp.protocols.tcp-ip.ibmpc Subject: Re: Western Digital board Message-ID: <8805111451.AA21000@trwind.ind.TRW.COM> Date: 11 May 88 14:51:44 GMT Sender: daemon@ucbvax.BERKELEY.EDU Organization: The Internet Lines: 21 One thing to watch out for with shared memory boards -- a number of AT clones do not honor the I/O CH RDY line on the bus. This signal is used by the memory to hold-off the processor for a little while. This is typically necessary when the on-board hardware is using its port into the shared memory. The consequence of not honoring I/O CH RDY is that the AT processor can pick up bad data because it fails to wait when told to do so. To build a shared memory board that does not have sensitivity to machines with this "feature" requires that the shared memory be essentially zero wait, which is increasingly difficult as machines get faster and faster and as LAN controller chips become more like I/O channels. Zero wait tends to imply that the raw memory speed is enough to satisfy both the LAN controller and the PC procesor simultaneously -- in other words we're talking about expensive, probably static, memory. ~I hope the folks who clone micro-channels do a better job than those who built clone AT buses. --karl--