Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!bbn!bbn.com!tchu
From: tchu@bbn.com (Tom Chu)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Looking for PC/AT bus specs
Summary: PC/AT bus specs
Keywords: PC/AT
Message-ID: <36897@bbn.COM>
Date: 7 Mar 89 17:44:59 GMT
References: <538@msn018.misemi> <4728@tekgvs.LABS.TEK.COM>
Sender: news@bbn.COM
Reply-To: tchu@BBN.COM (Tom Chu)
Organization: Bolt Beranek and Newman Inc., Cambridge MA
Lines: 26

Having worked on a PC/AT design myself, there is no such animal as a PC/AT bus
spec. In general you have to get the schematics and generate one your own
timing based on the schematic. The PC/AT bus is generally an extension of the
80286 bus with some extra signals for the state machines on the PC/AT. The
IBM/AT reference manual gives the description for all the signals that are not
relevant to the 80286. There are only 4-5 signals. If there are any specific
questions, then post the question, and I will answer to the best of my ability.
It has been quite awhile since I have looked at the IBM-PC AT.

Another fact that has never been ever figured out about the bus is the amount of
amps that can be drawn by an expansion board. The only limits that have been
imposed are by the rating of the connector and the size of the power supply.
So it is theoritically possible to blow up a power supply with one or two boards
plugged in !!!! Care must be taken when you expand you PC/AT.


There are other tid bits such as this around !! Anyone out there know at least
hardware flaws with the PC/AT architecture ?? The 2 I am talking about
basically affects the PC-AT performance.

Hint 1: Involves the hard disk.

Hint 2: Memory
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					T. Chu