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From: sjs@gnv.ifas.ufl.edu
Newsgroups: comp.sys.ibm.pc.misc
Subject: ISA/EISA
Message-ID: <1991Mar28.114156.104@gnv.ifas.ufl.edu>
Date: 28 Mar 91 16:41:56 GMT
References: <1991Feb25.174455.1109@bronze.ucs.indiana.edu> <14111@hacgate.UUCP>
Lines: 32

In article <14111@hacgate.UUCP>, tackett@ipla01.hac.com (Walter Tackett)
writes:

>i am buying an ibm pc clone with a 33MHz 80486 processor.  the dealer says 
>that it sports an ISA (as opposed to an EISA) bus architecture.   Is this guy
>full of sh*t or does it make a critical difference, or what? my understanding
>was that ISA is basically a 16-bit bus structure! RSVP FAST!  Please include
>any references to published material which may be of use to me.  Thank you
>in advance.
>-walter
>tackett@ipla01.hac.com
>sahtirn@ipla01.hac.com

ISA is Industry Standard Architecture, which is like what the IBM AT
had, a bus that could handle 8- and 16-bit cards.  EISA is Extended
ISA and is downward compatible with ISA cards.  An EISA slot can take
a 16-bit ISA, or an EISA-specific 32-bit card (the EISA card has a
special edge). So, the difference between ISA and EISA is the ability
to use 32-bit EISA cards. (An EISA PC may also have slot(s) for 8-bit
cards, I forget; but ask the dealer). 

You should get 8- and 16-bit slots, as that is what is required by
most cards, like hard/floppy, VGA, COM/LP, scanner cards, etc.  You
don't really need a 32-bit slot unless you have a card in mind that
uses it, or wish to have it for potential future use.  But then again,
the 32-bit slot can always take a 16-bit card. 

For myself, and for my own use, I might get one with one EISA slot
just in case I wanted a card that required it, but I wouldn't bother
with a PC that had more than one EISA slot. 

EISA first came out in 1989, so check PC mags dated with that year.