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From: raymond@ptolemy.arc.nasa.gov (Eric A. Raymond)
Newsgroups: comp.sys.ibm.pc,alt.msdos.programmer
Subject: VGA Memory Map & Base Addresses
Message-ID: <2117@edison.ptolemy.arc.nasa.gov>
Date: 31 Aug 89 08:55:23 GMT
Reply-To: raymond@ptolemy.arc.nasa.gov (Eric A. Raymond)
Organization: NASA Ames Research Center
Lines: 17

Could some kind soul enlighten me on the VGA memory layout?  More
specifically, the 640x480x2 graphics mode (also a MCGA mode).

For instance, CGA 640x200 memory is split into two blocks.  One at
B800 has every other line (odd).  One at BA00 (me thinks) has the other
every other line (even).  So it can be described by these two base
adresses.

So what are the base adresses of the VGA 640x480x2 mode.  Is it
linear (No even/odd scanline stuff)? Me thinks it starts at A000, but
are there any other base addresses (for odd lines).

FYI, this even/odd stuff is to simplify interlace logic on the
graphics card.  Is this used on the VGA?
-- 
Eric A. Raymond  (raymond@ptolemy.arc.nasa.gov)
G7 C7 G7 G#7 G7 G+13 C7 GM7 Am7 Bm7 Bd7 Am7 C7 Do13 G7 C7 G7 D+13: Elmore James