Q72013: Examining Contents of UMBs
Article: Q72013
Product(s): Microsoft Disk Operating System
Version(s): MS-DOS:5.0
Operating System(s):
Keyword(s):
Last Modified: 19-NOV-1999
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The information in this article applies to:
- Microsoft MS-DOS operating system version 5.0
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SUMMARY
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You can determine what programs and terminate-and-stay-resident programs (TSRs)
are loaded into upper memory blocks (UMBs) by first using the EMM386 command to
see where UMBs start, and then using the MEM/DEBUG (or MEM/Program) command to
see how the UMBs are being used.
NOTE: This article applies to MS-DOS version 5.0; it does not apply to later
versions of MS-DOS.
MORE INFORMATION
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If you run EMM386.EXE from the command line, it displays something similar to
the following:
MICROSOFT Expanded Memory Manager 386 Version 4.20.06X
(C) Copyright Microsoft Corporation 1986, 1990
Expanded memory services unavailable.
Total upper memory available . . . . . . 0 KB
Largest Upper Memory Block available . . 0 KB
Upper memory starting address . . . . . . C800 H
EMM386 Active.
The "Upper memory starting address" is the first segment in which UMBs are
located.
Use MEM/DEBUG to show memory usage. It displays something similar to the
following (note: you can make the output stop after each page by using
MEM/DEBUG|MORE):
Address Name Size Type
------- -------- ------ ------
000000 000400 Interrupt Vector
000400 000100 ROM Communication Area
000500 000200 DOS Communication Area
000700 IO 000A80 System Data
CON System Device Driver
AUX System Device Driver
PRN System Device Driver
<.. removed lines here to shorten output ..>
01A990 MSDOS 085650 -- Free --
09FFF0 MSDOS 028010 System Program
0C8010 MSDOS 000130 -- Free --
0C8150 MSDOS 000AE0 -- Free --
0C8C40 XNSBIOS 000120 Environment
0C8D70 XNSBIOS 002610 Program
0CB390 SESSION 000120 Environment
0CB4C0 PRTSC 000120 Environment
0CB5F0 PRTSC 000320 Program
0CB920 DOSKEY 000FE0 Program
0CC910 MIRROR 001990 Program
0CE2B0 MOUSE 003830 Program
0D1AF0 MSDOS 0064E0 -- Free --
0D7FE0 MSDOS 008020 System Program
0E0010 IO 001500 System Data
RAMDRIVE 0004A0 DEVICE=
D: Installed Device Driver
ANSI 001040 DEVICE=
CON Installed Device Driver
0E1520 SESSION 000410 Program
0E1940 REDIR 0093E0 Program
0EAD30 MSDOS 0052C0 -- Free --
656384 bytes total conventional memory
655360 bytes available to MS-DOS
625664 largest executable program size
4194304 bytes total contiguous extended memory
0 bytes available contiguous extended memory
3124224 bytes available XMS memory
MS-DOS resident in High Memory Area
Given the upper memory starting segment of C800, reported by EMM386, you can
examine the MEM/DEBUG output for any address greater than or equal to C8000.
Anything with "-- Free --" in the type column is available UMB memory. Anything
with a name other than MSDOS is a program or device driver that is running in a
UMB. In the example above, XNSBIOS, XNSBIOS, SESSION, PRTSC, DOSKEY, MIRROR,
MOUSE, RAMDRIVE, ANSI, SESSION, and REDIR are all running in UMBs.
The size is in Hexadecimal. In the example above, there are free UMBs at 0C8010
(size:130h) , 0C8150 (size:AE0h), 0D1AF0 (size:64E0h), and OEAD30 (size:52C0h).
If you are unfamiliar with Hex numbers, you can get a rough approximation of the
size of the block in K as follows:
(Multiply 10,000 digit by 16) + (Multiply 1,000 digit by 4) + (Divide 100
digit by 400) = K.
Thus, in the example above, the UMB at location OEAD30, size 52C0, is
(5*4)+(2/4)=20.5K.
REFERENCES
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More information on this subject can be found in the version 5.0 "Microsoft
MS-DOS User's Guide and Reference" and the version 5.0 "Microsoft MS-DOS Getting
Started" manual.
Additional query words: 5.00
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Keywords :
Technology : kbMSDOSSearch kbMSDOS500
Version : MS-DOS:5.0
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