Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!hellgate.utah.edu!dog.ee.lbl.gov!nosc!cod!bmarsh
From: bmarsh@cod.NOSC.MIL (William C. Marsh)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Dual monitors
Message-ID: <2819@cod.NOSC.MIL>
Date: 13 Feb 91 20:37:54 GMT
References: <26810@uflorida.cis.ufl.EDU> <91037.150254BUAD1621@Ryerson.CA> <26753@uflorida.cis.ufl.EDU> <166@cf_su20.cf_su10.Sbi.COM> <169@cf_su20.cf_su10.Sbi.COM>
Reply-To: bmarsh@cod.nosc.mil.UUCP (William C. Marsh)
Organization: Naval Ocean Systems Center, San Diego
Lines: 24

In article <169@cf_su20.cf_su10.Sbi.COM> nee@cf_su14.Sbi.Com (Robert Nee) writes:
>> I just discovered from someone over at comp.windows.ms.programmer that
>> supposedly the VGA cards out there all operate at 8-bit bandwidth 
>> when IN GRAPHICS MODE....is this true?  Even the 16-bit ones do.
>
>No.  This is not true.  However all VGA cards will operate in 8-bit mode
>ALL THE TIME if they are installed in a system with an 8-bit MDA board.

Sorry, the EGA/VGA interface is only 8 bits wide, so even if your VGA
connects to the '16 bit' connector, the board itself can only do 8 bits
at a time.  If you look at the memory architecture on the board, you will
also notice that it is (256, 512, ot 1024) x 8 bits.  All the cards 'fake'
16 bit accesses in graphics mode.

And anyway, all memory accesses to video memory is sync'd to H or V retrace
time, so 16 vr. 8 bits really don't amount to much.  (Even in the VRAM 
adapters too!  What a waste!)

Bill
-- 
Bill Marsh, Naval Ocean Systems Center, San Diego, CA
{arpa,mil}net: bmarsh@cod.nosc.mil
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"If you are not part of the solution, you're part of the problem..."