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From: mir@opera.chorus.fr (Adam Mirowski)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Upgrading 256K VGA to 512K VGA card
Message-ID: <7384@chorus.fr>
Date: 31 Dec 90 14:00:44 GMT
References: <62M^M8#@rpi.edu> <3370005@hpsgwp.sgp.hp.com>
Sender: mir@chorus.fr
Reply-To: mir@opera.chorus.fr (Adam Mirowski)
Organization: Chorus systemes, Saint Quentin en Yvelines, France
Lines: 16

As for the bus width problem: 16-bit-bus cards with 256x4 chips could be
internally 8 bit when equiped with only 2 chips (256 Kb) and become true
16 bits when equiped with more RAM. On my Trident 8900 (1Mb) card, there
are 8 slots for 256x4 chips. Why would one brain-damage a higher end card
with slow memory access?

Anyway: 16-bit cards are allowed three 125 ns bus cycles on every access.
They may request additional ones if they want but can't announce that
they don't need as much time. That makes 375 ns which is enough for the
card to perform many internal transfers, including multiple writes/reads
to/from its internal 8 bit memory.

Correct me if I'm wrong.
-- 
Adam Mirowski,  mir@chorus.fr (FRANCE),  tel. +33 (1) 30-64-82-00 or 74
Chorus systemes, 6, av.Gustave Eiffel, 78182 Saint-Quentin-en-Yvelines CEDEX