Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!iuvax!cica!tut.cis.ohio-state.edu!ucbvax!mtxinu!taniwha!paul
From: paul@taniwha.UUCP (Paul Campbell)
Newsgroups: comp.arch
Subject: Re: 386 machines are workstations? (Sun/386i)
Message-ID: <607@taniwha.UUCP>
Date: 31 May 90 16:10:51 GMT
References: <136288@sun.Eng.Sun.COM> <1990May30.041648.9063@ico.isc.com>
Reply-To: paul@taniwha.UUCP (Paul Campbell)
Organization: Taniwha Systems Design, Oakland
Lines: 21

In article <1990May30.041648.9063@ico.isc.com> rcd@ico.isc.com (Dick Dunn) writes:
>number of accesses to video memory.  Remember that a dumb frame buffer is
>not just a hunk of memory; it's a hunk of *dual-ported* memory, and the
>bandwidth appetite of a high-res fast-refresh display is enormous (by the
>standards of such machines).  Most of the memory's bandwidth goes into
>feeding the display; the CPU gets the leftovers.  Given that, it's not too
>hard to drive it to capacity with a 386.

It depends on the display design - remember on an AT class machine video
designers are 'stingy' (ie they are in cut-throat price competition) and
don't use VRAM (like for Mac and other high-end workstation displays),
VRAMs steal about 2% of the bandwidth. Also lots of the PC systems have
16-bit buses, meaning you have to do twice as many bus cycles to get
the same amount of work done ....

	Paul

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