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From: phil@diablo.amd.com (Phil Ngai)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Fastback DMA failure (8237A-5) defective chip
Message-ID: <28150@amdcad.AMD.COM>
Date: 28 Nov 89 00:02:39 GMT
References: <1247@adds.newyork.NCR.COM>
Sender: news@amdcad.AMD.COM
Reply-To: phil@diablo.AMD.COM (Phil Ngai)
Distribution: usa
Organization: Advanced Micro Devices, Inc. Sunnyvale CA
Lines: 17

In article <1247@adds.newyork.NCR.COM> ronb@adds.newyork.NCR.COM (Ron Beausoleil) writes:
|   This problem is only found on XT's using AMD dma parts.  AT's using this
|part do not have this problem.  Different circuit design.

The real story (although I am not an official spokesman) is that AMD
did the first generation of the DMA controller and licensed the design
to Intel who modified it a little and documented the enhancement. Boca
Raton designed to the Intel data sheet and didn't check to see if it
was downward compatible with AMD's design. It wasn't but until
Fastback came along there was no software which exposed the problem.
Since then AMD has incorporated the Intel enhancement in their chips
(it is a very simple change) and most motherboard makers use circuits
which are compatible with both generations of DMA controllers. 

--
Phil Ngai, phil@diablo.amd.com		{uunet,decwrl,ucbvax}!amdcad!phil
AT&T Unix System V.4: Berkeley Unix for 386 PCs!