Keyboard differences. Msdos 3.3 vs Msdos 5

[Twospruces]

May have nothing at all to do with the keyboard--both DOS versions use the INT 16H BIOS service for keyboard input.

The three-key salute (ctrl-alt-del) is trapped within the BIOS and initiates a reboot--doesn't indicate anything about the MSDOS functionality.

It sounds as if the system is hung in a loop or has gone out to lunch.

First step--strip the thing down to its basics. That is, no autoexec.bat or config.sys. If you have a hard disk, temporarily remove it. Try booting and running from floppy. If that works, add things in until it quits working.

Excellent suggestions. I will spend some time on that. It did not don on me that the machine could be hung as opposed to ignoring the keyboard.

A lot of things are different in DOS 5.

Are you absolutely sure DOS 5 is actually still running, and not hung? Perhaps put the command "CTTY COM1" at the end of you autoexec.bat and see if you can control the computer over a nullmodem cable. (I'm guessing it has a serial port).

If you specify other programs in the autoexec.bat, do they run but still not accept keyboard input?

You might try running various diagnostic programs under DOS 3.3 and see what they make of the keyboard. Perhaps find some games that are known to take direct control of the keyboard and see if they work under DOS 3.3.

If the keyboard I/O interface differs from standard IBM PC and clones, then many programs will have problems. The only ones that would work are ones that use the BIOS interface.

BTW, I was under the impression there at least had been some UMB programs that could load drivers in UMB memory even under DOS 3.3. Although newer ones are not likely to support 3.3. It is mostly a matter of tricking a TSR in to thinking the free memory starts at D000:0000, or wherever.

also excellent! great ideas. I'm not sure at all... I get a command prompt and thats it. I can certainly try different things as you suggest here.

thanks for the inputs, all.

[Twospruces]

Great suggestion here -->

Are you absolutely sure DOS 5 is actually still running, and not hung? Perhaps put the command "CTTY COM1" at the end of you autoexec.bat and see if you can control the computer over a nullmodem cable.

Got CTTY COM1: working over serial... and yes DOS 5 is running.
The copy of MSDOS5 that I have seems to require an install - many of the DOS files are in a ZIP folder. When I try to run the SETUP program, it stalls since I can't enter any keys.

So, I think at this point it is safe to say that MSDOS 5 is up and running, but ignoring the keyboard inputs.

[Agent Orange]

Here's link for the manual: https://oldcomputers.net/Zenith-Z-17...ors-manual.pdf

Manual says the OS is compatible with IBM PC-DOS and kind of hints that it may have been a special version for the Z. Not sure about that.

[krebizfan]

Appendix B of the owner's manual seems to show Z170 uses different key codes than the IBM PC.

[pcdosretro]

Is there a TSR which is loaded in MS-DOS 3.30 which you aren't loading in MS-DOS 5.0 ? It really sounds like a system incompatibility as MS-DOS 5.0 and later run fine on all IBM-compatible PCs which were pretty much everything by 1991 when it came out.

As for what's different about DOS 5.0 see my DOS history here - https://sites.google.com/site/pcdosretro/doshist

[Twospruces]

update:
1) the BIOS interrupt table appears correct when comparing the boot up with MSDOS 3.3 vs MSDOS 5. the INT 16h address is identical, so any int 16h calls should be serviced by the BIOS correctly.
2) I can see that the keyboard scan routines are putting correct keyboard data into the keyboard buffer at 40:1E. At least they look correct. also, the circular buffer pointers look correct.
3) I can use CTTY COM1 to speak to DOS no problem but when I issue the command CTTY CON...unable to enter keystrokes.


something is preventing MSDOS 5 from reading the keyboard buffer....

[Stone]

When you try to load DOS 5 do you get as far as a DOS prompt? IF so, does that mean that your config.sys and autoexec.bat files have been correctly executed? So the problem arises when you try to run a program from the command line, correct? If you can confirm that is what's actually happening please let us know. If not, where is the hangup occuring?

[Twospruces]

Yes, msdos 5 boots up to a dos prompt. if I include MODE and CTTY COM1 commands in autoexec.bat, then I can control the machine remotely.
So, imagine letting the machine boot right up, and you are looking at
A:\>

At this point, (assuming I did not redirect console to COM1), I cannot enter key strokes. They are however being placed into the keyboard buffer. When I exceed 16 characters, BIOS beeps indicating buffer full.

DOS is not hung. I have a cursor blinking and I am pretty sure if I could redirect console to COM1, I could regain control.

I noticed that the Zenith BIOS is not using BDA above 40:7F. There is basically garbage above. So, the pointers to the keyboard buffer are no good. I tried placing default values during boot up (using XUB) in 40:80 and 40:82 which are pointers to the start of the keyboard buffer - no improvement.

anyhow, a good puzzle. I was really thinking that the bad data in 40:80 and 40:82 were the smoking gun. If DOS didnt know where to look for the keyboard entries, that would explain a lot.

[Twospruces]

success is mine....

there is one more byte that needs to be initialized. 40:96 , which is a keyboard flag byte. Again using XUB to tweak BDA values, I reset that byte to 00.

Guess what, now I have a keyboard working with MSDOS 5!

thanks for the assistance.

[Stone]

Excellent!