Ref: 11420011
Title: Video Mapping for 3+ PC Servers Using 3ComEMM
Date: 1/29/90

Copyright 3Com Corporation, 1991.  All rights reserved.

The VIDMEM= parameter reserves memory for video and makes
accessible all of the available high DOS memory below the video
area.  For example, for EGA, VGA, and CGA adapters, the statement
VIDMEM=B800-C000 will reserve that space of memory for them, then
backfill (recover memory) from A000-B800 for a total of 736 KB of
conventional memory.

Note:  The USE= parameter makes available areas of high DOS, but if
they are not contiguous they cannot be used by 3ComEMM.  Because
USE= does not increase low DOS memory, it is better to use the
VIDMEM= parameter.

Color Monitors:

A000      B7FF B800          C000
 |96 KB  ||        CGA Video       |
 +--------------------------------++------------------------+
       Total after recovery:        VIDMEM=B800-C000
       736 KB of base memory



A000B000          B800       C000
 |   Reserved for graphics        |  Unused    |  EGA/VGA Video  |
 +--------------------------------+------------+-----------------+
 VIDMEM=B800-C000
 <---- 3ComEMM recovers all 96 KB for a   ---->
 <---- total of 736 KB of low DOS memory  ---->


Monochrome Monitors:

Monochrome monitors do not reserve an area for high resolution graphics
like EGA and VGA adapters.  Under normal conditions, monochrome adapters
reside at B000-B800 and 3ComEMM backfills all available memory from
A000-B000 for a total of 704 KB memory.  No more than 704 KB is
recovered because monochrome video adapters are mapped closer to A000
than EGA, VGA, and CGA adapters.

A000B000          B800       C000
 |       | Monochrome |                 |
 +--------------------------------+------------+-----------------+
       Total after recovery    VIDMEM=B000-B800
       704 KB of base memory

