UMB Support, Floppy-Based Programs, and Compaqs (70915)

The information in this article applies to:
    Microsoft MS-DOS operating system 5.0
    Microsoft MS-DOS operating system 5.0a
    Microsoft MS-DOS operating system 6.0
    Microsoft MS-DOS operating system 6.2
    Microsoft MS-DOS operating system 6.21
    Microsoft MS-DOS operating system 6.22

This article was previously published under Q70915


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).


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.


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.


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.

Modification Type: Major Last Reviewed: 5/12/2003
Keywords: KB70915