#392 Invalid Opcode at E923

[Jens Bongartz]

Hello everybody,

first of all thank you for creating and maintaining the FreeDOS project.

I installed FreeDOS on a vintage Compaq Deskpro 386/20 (the first 386 line ever - even before IBM) unsing the 720kB disk option. The installation process went flawless.
Unfortunately when I boot the systems crashes. In boot-option 2 (more compatible) and 4 (Safe Mode) it ends in a black screen. In boot option 5 (Emergency Mode) I get the following printout (see also attached photo):

HimemX 3.36
KBC A20 method used
FreeCOM version 0.85a - WATCOMC - XMS_Swap

Invalid Opcode at E923 11DF 0202 7661 FF61 ECEB 28A1 8500 75C0 E805 FF99 C085 2B75
Cannot terminate permanent FreeCOM instance
System halted

First I supposed a faulty RAM - but with another RAM-card I get exactly the same error.

Any suggestions?

Thanks
Jens

[Jens Bongartz]

Sorry, I must correct myself:
In boot-option 2 (more compatible) I get a black screen.
In boot-option 4 (Safe Mode) I get the mentioned error message.
Boot-option 5 (Emergency Mode) works and I reach the prompt.

Best
Jens

[fritz.mueller]

Hi,
first of all thanks for using FreeDOS.
As I learned that it is always good to understand what you really did, some questions:
You installed FreeDOS with a 720 kB diskette? Did you use something else than a diskette?
The diskette booted up without any problems?
You were able to install the whole diskette to the HD without any problems? Any strange messages (HD is full or something else?)
Which version did you use (1.3 or FDT2402=most actual)
(Sounds crazy why I ask this, but this is important to know if the Computer works fine with the diskette or not. If it boots up from there the problem is closer to the HD than to the other parts (mainboard, RAM etc.).
As a first thing I would recommend to run chkdsk c:, dosfsck c: mem and (not really important) defrag c: from diskette, or, if it was installed, from HD, to find out if the HD itself is okay. If the commands are not on the diskette you can get them in different ways. E.g.: https://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/dos/
As a second I would download the latest FD version FDT2402, see: https://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/distributions/test/ as there are many changes, especially with fdisk.
Please check this and tell if it helped.
As a third, when booting up from HD there should appear a short message with informations about the HD, e.g. its size, its Cylinder / Sector / Header settings (CHS) and if FreeDOS expected other values.. This information maybe helpful too.
As a fourth it would be fine if you could execute fdisk from FDT2402 and report the size of HD,
the numbers of partition and their sizes (see diagnostic system, should be at least two partitions). Do not delete or modify them, simply press ESC when you know the values.

If I remember right, Compaq had a diagnostic system on a special partition of the HD that could be started by pressing by one of the Function keys (maybe F10 or F12?). What do these diagnostic tools say?
Thx for response

Fritz

[Jens Bongartz]

Hi Fritz,
thanks for your reply.
I downloaded the most recent version from the FreeDOS website.
freedos.org/download >> For classic hardware >> FD13-FloppyEdition.zip

From the 720k folder I copied the 11 disk images to a usb stick. I am using a GOTEK drive with flash floppy to emulate a floppy disk drive. The whole installation process was flawless without any error message.
As written in my previous not visible message (awaiting moderation) I can boot from the HD in "Emergency Mode". The HD seems fine. The error message with "invalid opcode" appears in "Safe Mode" and the systems crashes with black screen in "more compatible" mode.
I will do the other HD checks when I am back home and I have access to the Compaq 386. And yes there is a diagnostic disk and everything seems fine. As mentioned the HD boots and I can see the boot manager with the different options (see photo attached). But then I am stuck - except in "Emergency Mode".
Thanks for your help.
Jens

[Jim Hall]

That Invalid opcode error can come from running JEMMEX on a machine that's less than a 386. You said that this machine was "the first 386 line ever" so it's possible this early 386 CPU isn't responding correctly to an instruction that works fine on later 386 CPUs.

Try commenting out the JEMMEX line from FDCONFIG.SYS (or build your own custom FDCONFIG.SYS that doesn't load JEMMEX) and see if that fixes it.

[Jens Bongartz]

Thank you Jim for your reply.
I commented out JEMMEX in FDCONFIG.SYS and FreeDOS booted with boot option 2. The same when I commented out HIMEMX for boot option 4.
The next time with JEMMEX active FreeDOS booted as well with the JEMMEX error "No supported A20 method detected". (see photo attached). Maybe this is a hint what is going wrong?
I cannot really believe that the 386 opcodes changed within its lifespan. Maybe JEMMEX is compiled with some special 486 options?

Thanks
Jens

[Jim Hall]

You can try experimenting with different A20 settings in JEMMEX. See JEMMEX /? for usage, but here are the two A20 settings you can explore:

+A20/NOA20     A20-disable emulation on/off (default on)
 A20METHOD:m   set A20 switch method. Possible values for <m> are
               KBC, PS2, BIOS, FAST, PORT92 and ALWAYSON.
...
 '+': option can be set dynamically by running JemmEx from the command line

JEMMEX is loaded during FDCONFIG.SYS, so you can try the new settings by editing that file.

This is the nature of DOS. Things usually "just work" ... but you sometimes had to create custom configs for different hardware.

[Jens Bongartz]

Dear Oliver,
thank you for your detailed reply and explaination. I will try it out and report back. I am eager to know which stepping my 386 is.
Cheers
Jens

[Jim Hall]

Just checking in on your tests - did it work?

[Jens Bongartz]

@Fritz: chkdsk c: worked flawless. See attached photo.

[fritz.mueller]

OK, so it is no hardware but a software problem. You should test the different options of jemmex or jemm386, see: https://www.bootablecd.de/FreeDOS-Internet-version/help110-no-fish/en/index.htm , look for jemmex or jemm386 or himemx there, or run "jemmex /? | more" for getting help.
The latest executable version is available here: https://github.com/Baron-von-Riedesel/Jemm