Q70915: UMB Support, Floppy-Based Programs, and Compaqs

Article: Q70915
Product(s): Microsoft Disk Operating System
Version(s): MS-DOS:5.x,6.0,6.2,6.21,6.22
Operating System(s): 
Keyword(s): 
Last Modified: 17-DEC-2000

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The information in this article applies to:

- Microsoft MS-DOS operating system versions 5.0, 5.0a, 6.0, 6.2, 6.21, 6.22 
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SYMPTOMS
========

On some Compaq computers, using the DEVICEHIGH or LOADHIGH command to load a
program or device driver located on a floppy disk into an upper memory block
(UMB) in the E000-EFFF region may cause the machine to stop responding (hang).

CAUSE
=====

This problem is caused by a faulty ROM BIOS belonging to the 386GROM family,
revision number H.5 through J.4. To identify a machine with one of these ROMs,
look at memory location F000:FFE4 for G5H through G4J.

WORKAROUND
==========

The workaround for this is to exclude the E000-EFFF region of upper memory using
the X=E000-EFFF parameter on the device=EMM386.EXE line in your CONFIG.SYS file.

MORE INFORMATION
================

With these faulty ROMs, it is impossible to use direct memory addressing (DMA)
to access the 64K region starting at E000. When attempting to load a program or
device driver from a floppy drive into this region using DMA, the ROM BIOS disk
access handler (interrupt 13) for the floppy controller changes the disk read
operation into a verify option. The ROM BIOS does not return an error to MS-DOS
in this case.

The products included here are manufactured by a vendor independent of Microsoft;
we make no warranty, implied or otherwise, regarding these products' performance
or reliability.

Additional query words: 6.22 5.00 5.00a 6.00 6.20

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Keywords          :  
Technology        : kbMSDOSSearch kbMSDOS621 kbMSDOS622 kbMSDOS620 kbMSDOS600 kbMSDOS500 kbMSDOS500a
Version           : MS-DOS:5.x,6.0,6.2,6.21,6.22

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