Newsgroups: comp.os.ms-windows.misc
Path: cantaloupe.srv.cs.cmu.edu!das-news.harvard.edu!noc.near.net!howland.reston.ans.net!gatech!hubcap!news
From: charlea@eng.clemson.edu (charles allen)
Subject: Re: Question on EISA video board performance
Message-ID: <1993Apr30.122333.828@hubcap.clemson.edu>
Sender: news@hubcap.clemson.edu (news)
Organization: Clemson University
References: <C68uBG.K2w@world.std.com>
Date: Fri, 30 Apr 1993 12:23:33 GMT
Lines: 44

From article <C68uBG.K2w@world.std.com>, by cfw@world.std.com (Christopher F Wroten):
> I have an EISA machine and I just do not understand why most
> EISA video cards only match the performance of their ISA
> counterparts. For instance, the EISA Orchid Pro Designer IIs-E is
> only about as "fast" as the ISA Diamond SpeedStar Plus, which isn't
> what I would call "fast."
> 
> I don't understand why EISA video cards aren't, as a group, on the
> same level of performance as Local Bus cards, given that EISA video
> cards have a 32 bit bus to move data around, instead of ISA's 8 bits.
> 
Good question.
Answer: The EISA bus does move 32 bits rather than ISA's 8/(16?)
        But it still moves it at about the speed as the ISA bus.
        I think that's either 8 or 10 mhz.
        The local bus designs also move 32 bits like the EISA, but
        they move the data at the cpu speed, up to 40 mhz.
        So, on a 33mhz cpu, the local bus is moving 32bit data at
        33 mhz, and the EISA is moving 32bit data at 8 or 10 mhz.
        So the local bus should be 3 to 4 times faster than EISA on
        a 33 mhz cpu.  EISA should be about two (maybe 3) times as
        fast as ISA.

> Since they are not, why would anyone (me included) pay a higher
> cost for a EISA video card when its performance is no better than
> and often worse that a much cheaper ISA video board, such as a
> Diamond SpeedStar 24X? From PC Magazine's (I think) recent report,
> I know that ATI makes a pretty fast EISA video card, but it's
> around $500, which is just about double what my wallet will allow
> me to spend. And, for $500, I could get a Diamond Viper and still
> have $100 left over (of course, I'd have to get a Local Bus mother-
> board too...)
> 
That's a very good question.  The EISA bus does have more advantages
over the ISA bus than just it's width.  For example: more/better 
interrupts and bus mastering.  But these other factors do not impact
 a video card very much.  They have more impact on file servers with 
multiple hard drives, full-throttle network cards, cd-roms, etc.

> Can anyone shed some light on my confusion/frustration?
> 
> Thanks!   Christopher Wroten, cfw@world.std.com
> 
> 
