Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!helios.physics.utoronto.ca!ists!yunexus!xrtll!silver
From: silver@xrtll.uucp (Hi Ho Silver)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Upgrading 256K VGA to 512K VGA card
Message-ID: <1990Dec29.172521.25431@xrtll.uucp>
Date: 29 Dec 90 17:25:21 GMT
References: <62M^M8#@rpi.edu> <3370003@hpsgwp.sgp.hp.com>
Reply-To: silver@xrtll.UUCP (Hi Ho Silver)
Organization: Not around here, pal!
Lines: 23

In article <3370003@hpsgwp.sgp.hp.com> plim@hpsgwp.sgp.hp.com (Peter Lim) writes:
$Two 256Kx4 RAM chips only give you 256K x 4 / 8 = 128K byte RAM.

   Wrong.  One 256Kx4 RAM chip gives you 256Kbitsx4/8=128Kbyte RAM.  Two
256Kx4 RAM chips give you 256Kx4x2=256Kx8=256Kbytes.

BUT

   It's only 8 bits wide, and putting 8-bit RAM on a a 16-bit VGA card is a
rather daffy idea (either that, or a sleazy marketing trick).  Yeah, it's
possible to add some circuitry to make it appear to be 16 bits wide, but
the fact is you're never going to get more than 8 bits at a time out of
it.  I can design a 16-bit-wide interface to a 1Mx1 chip, and it will seem
to the CPU to be 16 bits wide.  No problem, if you don't mind a greatly
diminished MTBF and losing about 94% of the performance.

   So, Phil, would you care to tell us all about how this particular
chipset gets 16-bit access to 8-bit memory?
-- 
 __            __  _  | ...!nexus.yorku.edu!xrtll!silver |  always
(__  | | |  | |_  |_) >----------------------------------< searching
 __) | |_ \/  |__ | \ | if you don't like my posts, type |    for
_____________________/  find / -print|xargs cat|compress |   SNTF