Ref: 02360001
Title: Physical Addressing in Protected Mode--DOS 5.0 and LAN Manager 2.0c
Date: 8/26/91

Copyright 3Com Corporation, 1991.  All rights reserved.


There is a problem with DOS 5's EMM386 in conjuction with DOS 5's
REDIRECTOR for LAN Manager 2.0c when loading the redirector HIGH and
using the 3C603 adapter.

When the redirector is loaded HIGH via EMM386,the workstation logs on as
a guest instead of a user.  Therefore, any network request such as NET
USE X: \\SERVER\SHARE drops the workstation from the network.

To solve the problem, use DMA channel 0.  By doing so, DMA is disabled
and the adapter uses Programmed I/O.

Explanation:  When EMM386 is loaded, it switches CPU into VIRTUAL 86
MODE (enhanced 386 mode).  The memory then becomes virtual, not
physical.  When the adapter is in DMA mode it issues a DMA request and
gives a physical address, not knowing that the CPU has remapped memory
virtually.  The end result is data corruption due to memory overlapping.

