XTMax: every DOS program using EMS crashes 4DOS 8.0 (or any TSR which allocated a chunk of EMS)

[pawosm-arm]

I've configured 4DOS 8.0 for using EMS as a swap. It worked well with lotech's 2MB EMS card. Now as I've replaced it with XTMax, I'm observing something weird. When I'm returning to DOS (4DOS) from any program (game) using the EMS memory (e.g. Microweb, Wolf8086, Commander Keen 4), the system gets crashed with a message from 4DOS about the EMS corruption. I don't recall seeing it before...

4DOS unrecoverable error EM

Also the XTEMM driver is bigger than LTEMM. When I load it high into UMB, there's not much space left, and the 11kB packet driver for the network card does not fit into there anymore. So far I didn't observe any negatives from this, and even the RAM hungry games as Test Drive 3 still work, so it's a minor inconvenience with no practical significance. Maybe it's worth combining UMB and EMS driver into one and keep its parts in both RAM and UMB?

[pawosm-arm]

For a reference, the C:\CONFIG.SYS file:

DOS=UMB
DOSDATA=UMB
rem DEVICE=C:\UMB\USE!UMBS.SYS
DEVICE=C:\XTMAX\XTUMBS.SYS D000-E000
BUFFERS=20
FCBS=3,3
FILESHIGH=30
LASTDRIVEHIGH=D
STACKSHIGH=42,512
SET DOSDIR=C:\DOS
rem DEVICEHIGH=C:\PICOMEM\PMEMM.EXE /p:E000 /i:268
rem DEVICEHIGH=C:\LTEMM\LTEMM.EXE /p:E000 /i:260
DEVICEHIGH=C:\XTMAX\XTEMM.EXE /P:E000 /N
rem DEVICE=C:\SCATEMM\SCATEMM.SYS IOADDR=208
rem DEVICEHIGH=C:\XTMAX\XTSD.SYS
INSTALLHIGH=C:\AMSTRAD\MOUSE.COM
SHELLHIGH=C:\4DOS\4DOS.COM C:\4DOS\ /P

the C:\AUTOEXEC.BAT file:

@ECHO OFF
PATH C:\BAT;%DOSDIR%\BIN;C:\TOOLS
SET BLASTER=A220 I5 D1 T3
rem Following line commented out by 4DOS INSTALL
rem SET COMSPEC=C:\DOS\COMMAND.COM
SET TMP=C:\TMP
SET TEMP=%TMP%
SET LIB=C:\QUICKBAS
SET LANG=EN
SET MTCPCFG=%DOSDIR%\MTCP.CFG
SET WATTCP.CFG=%DOSDIR%
SET NLSPATH=%DOSDIR%\NLS
SET HELPPATH=%DOSDIR%\HELP
rem C:\PICOMEM\PMINIT.EXE
C:\UMB\TEST!UMB.EXE
rem LH C:\PICOMEM\FREESPT C
rem LH C:\PICOMEM\PM2000 0x60
LH C:\SMC8003\SMCPKT5\PKT8000 -i 0x60
LH C:\4DOS\KSTACK.COM
BORDER 5

the C:\4DOS\4DOS.INI file (using EMS is the default as long as a path to a swapfile is not specified):

[4DOS]
InstallPath = C:\4DOS\
UMBLoad=Yes
UMBHistory=Yes
UMBDirHistory=Yes
UMBEnvironment=Yes
UMBAlias=Yes
UMBFunction=Yes
Environment=384

EDIT: I've also tried a C:\CONFIG.SYS file prepared more like the README file advices it (XTEMM.EXE before XTUMBS.SYS), sadly, it does not improve anything (4DOS still crashes when I exit from Microweb and alike):

DOS=UMB
DOSDATA=UMB
rem DEVICE=C:\UMB\USE!UMBS.SYS
DEVICE=C:\XTMAX\XTEMM.EXE /P:E000
DEVICE=C:\XTMAX\XTUMBS.SYS D000-E000
BUFFERS=20
FCBS=3,3
FILESHIGH=30
LASTDRIVEHIGH=D
STACKSHIGH=42,512
SET DOSDIR=C:\DOS
rem DEVICEHIGH=C:\PICOMEM\PMEMM.EXE /p:E000 /i:268
rem DEVICEHIGH=C:\LTEMM\LTEMM.EXE /p:E000 /i:260
rem DEVICE=C:\SCATEMM\SCATEMM.SYS IOADDR=208
INSTALLHIGH=C:\AMSTRAD\MOUSE.COM
SHELLHIGH=C:\4DOS\4DOS.COM C:\4DOS\ /P

EDIT: loading EMS driver low before UMB .is. the only correct way of doing it. Microweb (see below) won't load pages otherwise.

[pawosm-arm]

Specifically, I don't think Microweb has it wrong and it works well with XTMax's EMS memory. Until I try to return to DOS.

[pawosm-arm]

Note: I've tried XTEMM.EXE /3 to force EMS 3.2 protocol support. It didn't help, 4DOS still crashes when exiting Wolf8086.

[pawosm-arm]

Even returning from Borland's emstest causes 4DOS crash...

[mbucchia]

Also the XTEMM driver is bigger than LTEMM. When I load it high into UMB, there's not much space left, and the 11kB packet driver for the network card does not fit into there anymore.

Hi, the driver is bigger because it needs to support 16MB vs 2MB. This means allocating an array of metadata for 8x more pages.

Even returning from Borland's emstest causes 4DOS crash...

EMSTEST.COM is working fine here (I ran it yesterday) however I don't use 4DOS. I will give that a try when I have a chance.

[mbucchia]

If you wish to reduce the size of the XTEMM driver (and therefore reduce the capacity of the EMS memory, because you do not need 16MB), you can do the following:

• Edit this line of code:

PAGE_MAX		EQU	2048	;max logical page count

This value is currently set up for a maximum of 32MB (2048 * 16KB). If you only care for 8MB for example, reduce the value to 512.

• Rebuild the driver. Open a command line prompt (cmd.exe) into the XTMax\Drivers\LTEMM folder and execute the following command:

..\Driver_Build_Tools\DOSBox\DOSBox.exe -conf Build.conf

Note that this command has a tendency to fail on the first try... So just run it a second time if needed.

A new tailored XTEMM.EXE driver will be output in the LTEMM folder and should be ready for you to use.

[pawosm-arm]

Hi, the driver is bigger because it needs to support 16MB vs 2MB. This means allocating an array of metadata for 8x more pages.

Well, XTMax has replaced the lotech's 2MB EMS card, my Teensy has 8MB soldered in (on a single chip; the place for the second chip has been left unoccupied), so it is way more than I need.

This value is currently set up for a maximum of 32MB (2048 * 16KB). If you only care for 8MB for example, reduce the value to 512.

I'll try to tailor it to 2MB.

EMSTEST.COM is working fine here (I ran it yesterday) however I don't use 4DOS. I will give that a try when I have a chance.

I never said it doesn't work. Quite contrary, it passes all of its tests. It's the 4DOS that crashes after returning from EMSTEST.COM or any other EMS-utilizing program.

[mbucchia]

I'm not familiar with 4DOS, so what I meant is that EMSTEST completes and returns properly to the command prompt, and you can run further applications after that. Obviously your issue is specific to 4DOS, and until I download and try that program, all I can say is that the issue is not systemic to the use the EMS driver, but rather a specific interaction with this 4DOS program.

[pawosm-arm]

Rebuild the driver. Open a command line prompt (cmd.exe) into the XTMax\Drivers\LTEMM folder and execute the following command:

I'm using DOSBox on Linux, but this rebuilding method also works there; the only thing I had to do was to change the slashes in the Build.conf file:

diff --git a/XTMax/Drivers/LTEMM/Build.conf b/XTMax/Drivers/LTEMM/Build.conf
index 7494c04..4064489 100644
--- a/XTMax/Drivers/LTEMM/Build.conf
+++ b/XTMax/Drivers/LTEMM/Build.conf
@@ -2,7 +2,7 @@
 @ECHO OFF
 CLS
 MOUNT C .
-MOUNT D ..\Driver_Build_Tools\TASM2
+MOUNT D ../Driver_Build_Tools/TASM2
 SET PATH=D:\
 C:
 MAKE > LOG.TXT

I'll try to tailor it to 2MB.

So after I've set PAGE_MAX to 128, it indeed limited the amount of usable EMS to 2MB and the driver is considerably smaller. As before, 4DOS has started and according to EMMSTAT, it successfully claimed its 272kB of EMS. Also, exiting from EMSTEST causes 4DOS failure as before.

A strange thing has happened to Microweb. When started without any parameter, it now exits to DOS with the Interrupt divide by zero, stack: message right after entering the VGA graphics mode. I rarely start it without giving an URL as a parameter, but I don't think I saw it before. Nevertheless, when started with an URL (e.g. microweb http://theoldnet.com or microweb http://frogfind.com), it seems to work fine and is still able to load images into EMS.

[pawosm-arm]

I'll try to tailor it to 2MB.

Yet there is also some good news here. I've tried to load XTEMM2MB high, and after that, there is still enough UMB to fit the packet driver in there. And Microweb still opens the web pages! Seems the problem with Microweb was not about XTEMM loaded high, but with the packet driver loaded low.

[pawosm-arm]

Some observation I've made, not sure if it is of any importance: during normal operation, the LED on Teensy blinks intensively, but as 4DOS throws the 4DOS unrecoverable error EM message, the LED on Teensy shines continuously, no more blinking, as if the code on Teensy just stopped to work. Could it be that the crash isn't in 4DOS or in the EMS driver, but in the Firmware itself?

[pawosm-arm]

One more observation: I've commented out loading the UMB driver in the C:\CONFIG.SYS file, so everything got loaded low. With EMS driver still being loaded, 4DOS is still using it. And after returning from EMSTEST and throwing the usual 4DOS unrecoverable error EM message, the system didn't crash and returned to the DOS shell! And the LED on Teensy still blinks vividly. Everything seemed fine, until I started EMMTEST.EXE: it crashed with the 4DOS server error -- EMS mapping failed message (yet the LED on Teensy still blinks).

[pawosm-arm]

Shouldn't the firmware drop some error message on a crash? I've connected the Teensy mounted on XTMax over a power-cutting USB 2.0 hub to my PC, started Arduion IDE, attached its Serial Monitor to the /dev/hidraw4 (which appeared and got recognized by Arduino IDE as soon as I've powered up the XT machine), and... nothing appears in the Serial Monitor, not even during the crash.

[pawosm-arm]

Some other note: CheckIT memory tests fail on EMS bullets.

The final report has been more specific about it:

EXPANDed Memory...Passed
High Address Lines...FAILED ***
ERROR at 1792K -- Ran out of EMS memory to test.
ERROR at 1792K -- Ran out of EMS memory to test.

Considering 2MB EMS visible to the EMS driver, the difference between 2048k and 1792k is exactly the amount occupied by 4DOS, so I guess it's the CheckIT this time that didn't expect a resident program could be occupying a part of EMS... (but wait! wasn't Sidekick resident doing the same? Or those remote-disk-drive-over-serial-port residents like desklink? Sadly I don't have them here to make sure).