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EDR-DOS development (Announce)

posted by ecm Homepage E-mail, Düsseldorf, Germany, 16.08.2023, 10:06

> >1. Why do you want to clear only 12h bytes at 0:500h rather than 20h
> bytes?
>
> >2. Can you describe the failure without your disk.asm change not to do
> something with diskette units?
>
> >3. Why did you change the colour offset? It seems like 24, 25, 26 points
> after the CON device header and its "COLOUR" signature while you subtract
> 6. So it actually uses the signature as data.
>
> >4. I don't think unsupported subfunctions of a partially supported int 21h
> service 71h function should return 7100h.
>
> >5. Finally, what name (if any) do you want me to enter into the repository
> for changes I pick from your patches?
>
> >6. Also, I haven't used it in a long time so I'm unsure what setup (if
> any) the HX extender needs in order to run MSWindows programs.
>
> >7. Can you list the exact commands or actions that I can do to reproduce
> the errors, please?
>
> 1. I did it for my own use. On my boot disk, I use a different kernel
> loader and store interrupt vectors 13h and 15h Linux/GRUB4DOS at address
> 0:0512 for later transfer to UMB memory and back after Int19h. Data at this
> address was probably used only by GWBasic.
Okay, I can do that. I don't think this patch will do any harm.

> 2. I don't remember now, it was 3 years ago. I'm using a little Linux and
> GRUB4DOS to run DOS because I don't have a floppy drive anymore. The disk
> drive is emulated and is somewhere in memory above 1MB. Without this fix,
> it just freezes.
All right.

> 3. I did it so that the DOS interrupts were stored at a fixed address
> 0070h:0100h
Oh, I missed that you also commented out the db "COLOUR" signature itself. This is the wrong way to achieve the correct address for vecSave. In my repo I already did it the right way.

> 4. Some programs (7zip launched with the command to unpack the archive
> using HX-DOS) only understand the code 7100h. When the code 0001h is
> returned, they assume that the file/directory cannot be created and abort
> without executing short file name function (39h).
Does this apply to all uses of error code 0001h in lfn.asm or only some? At least function 7142h with cl > 2 should return error 0001h I think.

> 5. You can use any name (e.g. CandyMan fix).
Okay.

> 6. HX configuration: any XMS driver and C:\HX\BIN in the PATH environment
> variable and running HXLDR32.EXE resident
>
> 7. Programs to reproduce the error: just run DN.EXE or 7Z a -mx Archive.7Z
> *.*
Thanks. I may have time to try this later, probably within the week.

> The way it compresses the kernel:
> https://megawrzuta.pl/download/c3100b23f1dc691db9e9e9b693d256d4.html
Interesting, thanks! I do have some comments:

Can you describe fix-bio's use of virtual and load dword / store dword? I am not used to FASM specific directives. The load and store access and change data that is already assembled? file is like NASM incbin? virtual assembles into a space that is discarded afterwards, just for access with load?

The registers don't all need to be preserved by fix-bio. es, di, si, bx, and cx are probably not used by the EDR-DOS load protocol. dl, ds, bp, ss, sp may be used.

I don't like the use of the memory at 004F0h for saving the registers. It would be better to use the stack or at least 005F0h.

The fix-bio expects the compressed file to be < 64 KiB. Fair enough.

The mov word [cs:0], ax could be replaced by directly storing a 16-bit immediate to the memory, instead of going through AX. Hmm, may actually be the same length of instruction bytes.

The retf in fix-bio can be replaced by a jmp far immediate because the kernel must be loaded at 70h:0 (currently).

What are the first 8 bytes supposed to be in the upx-compressed drdos.com that are replaced by fix-dos? I think you could add load directives to check that those instructions match what you expect.

In the batch file you use "vasm". Is that a typo for "fasm"?

What versions of apack and upx do you use?

---
l

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