China DOS Union

Why does the same boot disk free up different amounts of UMB on different machines?
The maximum difference is actually as much as 50K!

Give the specific situation... talk about it...

This is a boot disk I modified based on wengier's 7.1. I found that on different computers the UMB size is different, and sometimes even the size of conventional memory is different too. I've thought about it over and over and still can't figure it out!
The contents of config.sys are as follows:
DEVICE=HIMEM.SYS
DEVICE=EMM386.EXE NOEMS X=D100
DEVICEHIGH=VIDE-CDD.SYS /D:IDE-CD
DEVICEHIGH=ASPICD.SYS /D:SCSI-CD
DEVICEHIGH=CLOAKING.EXE

DOS=HIGH,UMB,AUTO
FILESHIGH=30
BUFFERSHIGH=30,0
LASTDRIVEHIGH=Z
STACKSHIGH=9,256

The contents of autoexec.bat are as follows:
@ECHO OFF
PROMPT $P$G
LH DOSKEY >NUL
LH MOUSE >NUL
LH MOUSCLIP /M >NUL
LH DOSLFN /Z:CP936UNI.TBL >NUL

:RAMD
XMSDSK 8192 /Y
FINDRAMD>NUL
PATH=%RAMDRIVE%\SYSTEM;%RAMDRIVE%\MENU;%RAMDRIVE%\MENU\BAT;A:\;C:\;
MD %RAMDRIVE%\SYSTEM
MD %RAMDRIVE%\TEMP
COPY A:\COMMAND.COM %RAMDRIVE%\SYSTEM>NUL

SET COMSPEC=%RAMDRIVE%\SYSTEM\COMMAND.COM
SET TMP=%RAMDRIVE%\TEMP
SET TEMP=%RAMDRIVE%\TEMP


:CD
LH MSCDEX /D:IDE-CD /D:SCSI-CD /S /K >NUL
FINDCD /Q >NUL

%RAMDRIVE%

It's not that these two files of yours have a problem... the UMB you're talking about means RAMD, right? Please explain specifically how the UMB and conventional memory change under different hardware specs...

There shouldn't be any UMB available at all........
When loading emm386.exe there is no "RAM" parameter.....

Sorry, maybe my basic knowledge is insufficient, but the problem definitely exists. Even when I use wengier's dos7.1 I noticed this problem. Below are the results of running the mem command after booting with dos7.1:
computer 1.

Modules using memory below 1 MB:

Name Total Conventional Upper Memory
-------- ---------------- ---------------- ----------------
SYSTEM 34,928 (34K) 10,592 (10K) 24,336 (24K)
HIMEM 1,168 (1K) 1,168 (1K) 0 (0K)
EMM386 3,200 (3K) 3,200 (3K) 0 (0K)
COMMAND 7,424 (7K) 0 (0K) 7,424 (7K)
CTMOUSE 3,328 (3K) 0 (0K) 3,328 (3K)
PCCACHE 21,312 (21K) 0 (0K) 21,312 (21K)
XMSDSK 688 (1K) 0 (0K) 688 (1K)
MousClip 2,784 (3K) 0 (0K) 2,784 (3K)
VIDE-CDD 5,024 (5K) 0 (0K) 5,024 (5K)
CLOAKING 1,152 (1K) 0 (0K) 1,152 (1K)
IFSHLP 2,864 (3K) 0 (0K) 2,864 (3K)
KILLER 400 (0K) 0 (0K) 400 (0K)
DOSKEY 3,968 (4K) 0 (0K) 3,968 (4K)
MSCDEX 2,816 (3K) 0 (0K) 2,816 (3K)
SHARE 320 (0K) 0 (0K) 320 (0K)
ZENO 1,376 (1K) 0 (0K) 1,376 (1K)
DOSLFN 26,720 (26K) 0 (0K) 26,720 (26K)
ESCAPE 496 (0K) 0 (0K) 496 (0K)
Free 688,240 (672K) 640,192 (625K) 48,048 (47K)

Memory Summary:

Type of Memory Total Used Free
---------------- ----------- ----------- -----------
Conventional 655,360 15,168 640,192
Upper 153,056 105,008 48,048
Reserved 0 0 0
Extended (XMS) 132,999,712 9,016,864 123,982,848
---------------- ----------- ----------- -----------
Total memory 133,808,128 9,137,040 124,671,088

Total under 1 MB 808,416 120,176 688,240

Largest executable program size 640,176 (625K)
Largest free upper memory block 32,304 (32K)
MS-DOS is resident in the high memory area.
computer 2.

Modules using memory below 1 MB:

Name Total Conventional Upper Memory
-------- ---------------- ---------------- ----------------
SYSTEM 35,328 (35K) 10,736 (10K) 24,592 (24K)
HIMEM 1,120 (1K) 1,120 (1K) 0 (0K)
EMM386 3,200 (3K) 3,200 (3K) 0 (0K)
CLOAKING 1,152 (1K) 1,152 (1K) 0 (0K)
PCCACHE 21,312 (21K) 21,136 (21K) 176 (0K)
MSCDEX 2,816 (3K) 2,816 (3K) 0 (0K)
DOSLFN 26,720 (26K) 26,720 (26K) 0 (0K)
ESCAPE 496 (0K) 496 (0K) 0 (0K)
COMMAND 7,424 (7K) 0 (0K) 7,424 (7K)
XMSDSK 688 (1K) 0 (0K) 688 (1K)
VIDE-CDD 5,056 (5K) 0 (0K) 5,056 (5K)
IFSHLP 2,864 (3K) 0 (0K) 2,864 (3K)
KILLER 400 (0K) 0 (0K) 400 (0K)
DOSKEY 3,968 (4K) 0 (0K) 3,968 (4K)
CTMOUSE 3,328 (3K) 0 (0K) 3,328 (3K)
SHARE 320 (0K) 0 (0K) 320 (0K)
ZENO 1,376 (1K) 0 (0K) 1,376 (1K)
MousClip 2,784 (3K) 0 (0K) 2,784 (3K)
Free 589,552 (576K) 587,792 (574K) 1,760 (2K)

Memory Summary:

Type of Memory Total Used Free
---------------- ----------- ----------- -----------
Conventional 655,360 67,568 587,792
Upper 54,736 52,976 1,760
Reserved 0 0 0
Extended (XMS) 267,266,608 9,279,024 257,987,584
---------------- ----------- ----------- -----------
Total memory 267,976,704 9,399,568 258,577,136

Total under 1 MB 710,096 120,544 589,552

Largest executable program size 587,696 (574K)
Largest free upper memory block 1,280 (1K)
MS-DOS is resident in the high memory area.
－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－
As everyone can see, the difference in Upper Memory is very large! What's going on here?

That's right, what he said is true. Because on some computers there is very little Shadow Memory, while on others there is a lot. UMB mainly uses this memory, so the size is often different. But on most computers the UMB memory is around 150-160KB.

Also, may I ask, why was LASTDRIVEHIGH=32 in CONFIG.SYS changed to LASTDRIVEHIGH=Z?

Now I can relax.
Lastdevice?? I thought it was lastdrive!
Then what does LASTDRIVEHIGH=32 mean?

It is LASTDRIVE, there is no LASTDEVICE! LASTDRIVEHIGH=Z means LASTDRIVEHIGH=26.

This... it means the maximum drive letter that can be used...

Oh, hehe, my eyesight is too bad...
I thought the maximum could only go up to z.