Path: utzoo!attcan!uunet!ncrlnk!ncrcae!hubcap!gatech!rutgers!rochester!pt.cs.cmu.edu!andrew.cmu.edu!pgc+
From: pgc+@andrew.cmu.edu (Paul G. Crumley)
Newsgroups: comp.sys.ibm.pc.rt
Subject: Re: Expansion bus compatibility
Message-ID: <0XeLRWy00jaR00RUlp@andrew.cmu.edu>
Date: 16 Dec 88 20:51:46 GMT
References: <2211@spdcc.COM>,
	<174@cthce.ce.chalmers.se>
Organization: Carnegie Mellon
Lines: 21
In-Reply-To: <174@cthce.ce.chalmers.se>

Christer,

I guess it's obvious that the card that didn't work (the Adaptec AHA-1540 SCSI
host adapter) in the RT/PC doesn't really work in the AT either.  (just try
DMAing onto a video adapter or some other slow memory that inserts wait states)
This board is clearly broken by design.  (the IBM PC/AT Technical Reference
Manual is very clear about the use of this signal)

As for the problem with non-atomic reads and writes from system memory, try
setting the DMA channel to use "buffered" mode. (this is described in the RT/PC
Tehcnical Reference Manual)  This mode will force updates to be atomic and will
usually provide better performance too!

BTW:
How about using the IBM RT/PC SCSI adapter?  We use them here and they work
fine.  They have plenty of buffers so the performance is quite good.


Best Regards,

Paul