Open access to the Upper Memory Block (UMB)

To get access to the Upper Memory Block (UMB) which is allocated from the upper memory area (UMA) one have to load the Expanded Memory Manager EMM386.EXE. The UMA covers 384 KByte and is placed just above the 640 Kbyte conventional memory. The UMB cannot occupy the entire UMA as other things resides there.

Edit the CONFIG.SYS and update/insert these lines to access the UMB:

DEVICE=C:\DOS\HIMEM.SYS
DEVICE=C:\DOS\EMM386.EXE
DOS=HIGH,UMB

If not using expanded memory then free 64Kbyte UMB:

DEVICE=C:\DOS\HIMEM.SYS
DEVICE=C:\DOS\EMM386.EXE NOEMS
DOS=HIGH,UMB

There is allocated memory for Monochrome support in the UMA, but it can be included in the UMB instead:

DEVICE=C:\DOS\HIMEM.SYS
DEVICE=C:\DOS\EMM386.EXE NOEMS I=B000-B7FF
DOS=HIGH,UMB

Use HIGHSCAN in DOS 6.0+ to scan aggressively for UMB in the UMA (Can cause trouble):

DEVICE=C:\DOS\HIMEM.SYS
DEVICE=C:\DOS\EMM386.EXE I=B000-B7FF NOEMS HIGHSCAN
DOS=HIGH,UMB

Note if wanting better memory performance then one should take a closer look at UMBPCI.SYS, which is an Expanded Memory Manager that has been optimized for several motherboard chipsets.

Related Load drivers in high memory to save conventional memory
Related Load environment in high memory with DOS 7.0

More Info MS KB37242
More Info MS KB77083
More Info MS KB78557
More Info MS KB98508
More Info MS KB78433
More Info MS KB93375
More Info MS KB112816

Updated: 26 September 2007

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