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From: v127p9xg@ubvmsd.cc.buffalo.edu (Robert J Miskines)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: EISA vs. ISA
Message-ID: <51097@eerie.acsu.Buffalo.EDU>
Date: 13 Dec 90 11:39:27 GMT
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ISA is the 16-bit bus those of us with AT/Compatibles are familiar with. 
EISA is a 32-bit bus, where the first part of the bus is ISA-compatible
if im not mistaken... But, it has an additional set of 'fingers' for an 
additional 16 bits to go through.. I believe this is similar to the 8/16 bit  
slots in an AT/Compatible - the first section of the 16-bit bus is
8-bit compatible.. you can plug 8-bit cards into it. If your card has the    
additional 'finger set' for 16-bit work, even better.. EISA is the same way. 
It will take already existing 8 and 16 bit cards, as well as 32-bit. 

The whole arguement is over which interface will become 'standard', EISA or
MCA (Micro Channel Architecture), IBM's attempt to regain a mega-market share
by inventing something completely incompatible with anything already in use. 

If you purchase an MCA machine, all your conventional IBM-type cards are 
useless. The question - why would anyone bother with MCA? because it comes with 
the IBM name. I do not KNOW, but i have heard that MCA is inferior as far as
potential for data throughput, but, since IBM invented & supports it, people
(end users, 3rd party manufacturers of add-in cards, etc) have a tendency to 
support it as well. 

Your decision as far as which 32-bit machine to buy will probably include the
following points..   
1)  Which bus will eventually win out, and what of the loser? If you invest $$$
    in new machine and cards, and that bus loses out as far as standards, 
    you may be up the creek as far as future support..
2)  If you do go MCA, remember that you will haveto replace all your current
    cards. With EISA you would not have to do this. Also note that MCA cards
    are more expensive than ISA cards.. 



As far as i know, the only 32-bit cards out yet are memory cards... Is this
true?


Robert J Miskines
V127P9XG@ubvms.cc.buffalo.edu