DOS ain't dead

> Did you try 765 Debug, which is included in the 2M / 2MGUI package? Search
> for 2mgui19.zip
> Also TestFDC by Dave Dunfield. See: http://dunfield.classiccmp.org/img/

Thanks. I don't know any of them. I just tried TestFDC and it interacted some way with my FDD and makes a bit crazy fast head move sound but all tests failed

TESTFDC 1.16 - Copyright 2007 Dave Dunfield - All rights reserved.   
BIOS reports drive A: as Unknown.                                   
Testing as: 1.44M HD, 80-track                                       
250k Single-Density: Format !error (0) Overun                       
250k Double-Density: Format !error (0) Overun                       
250k Double/128byte: Format !error (0) Overun                       
500k Single-Density: Format !error (0) Overun                       
500k Double-Density: Format !error (0) Overun                       
500k Double/128byte: Format !error (0) Overun                       
                                                                     
Report on FDC capabilities, issued 28/03/2024 4:55:34:               
Single-Density at 250 kbps ............................ Failed       
Single-Density at 300 kbps ............................ Not tested   
Single-Density at 500 kbps ............................ Failed       
Double-Density at 250 kbps ............................ Failed       
Double-Density at 300 kbps ............................ Not tested   
Double-Density at 500 kbps ............................ Failed       
Double-Density at 250 kbps / 128 byte sectors ......... Failed       
Double-Density at 300 kbps / 128 byte sectors ......... Not tested   
Double-Density at 500 kbps / 128 byte sectors ......... Failed       


---
DOS gives me freedom to unlimited HW access.

2mgui19.zip contains only single file 2MGUI.EXE
Well I found 765DEBUG.EXE and also tried ImageDisk 1.2. It can properly detect disk RPM: 300 and it can seek the heads over disk but any attempt to read/write/format cause "Overrun" error, what does it mean? As there are no source available I cannot be sure it's not trying use DMA.

---
DOS gives me freedom to unlimited HW access.

> Did you try 765 Debug, which is included in the 2M / 2MGUI package? Search
> for 2mgui19.zip

For the record:
- 765DEBUG 5.0 binary: https://www.sac.sk/files.php?d=14
- 765DEBUG 5.0 sources: http://retro.icequake.net/dob/files/bleuge/765debug/SOURCE/

(The link at https://www.gm.th-koeln.de/~wmsr/sourcen/sources.html doesn't work anymore.)

---
Forum admin

> Actually, floppy diskette access seems to be a case where it's normal for
> the ROM-BIOS to use ISA DMA to access the disk. Consider
> the
> description of the int 13h error code 09h:

Yes. But it seems there was a few implementations of BIOS that didn't use DMA, I read that some HP Omnibook. That was probably the reason why Linux kernel floppy driver implemented both DMA and noDMA methods. So it's possible, I got it working under Linux (some floppies had problems but it's probably caused by theirs age).
I'm still looking for reliable noDMA implementation that can be used under DOS. Linux floppy driver has some depencies to Linux kernel and code pointed by Laaca from the doslib works very unreliable. I didn't have time to debug it yet...

---
DOS gives me freedom to unlimited HW access.

> Maybe here could be some DOS floppy code which does not rely to DMA
> https://github.com/joncampbell123/doslib/tree/master/hw/floppy

Hm, doslib, I downloaded this huge package some months ago but didn't have time yet to discover whats's all inside, seems to me a bit kludgy...

I just opened floppy.c and at the beginning of file I see
#include <hw/8237/8237.h> /* DMA controller */

this doesn't persuade me that this code don't use DMA...

EDIT: there seems to be maybe something nondma too:
floppy_controller_wait_data_write_non_dma_ready()
it will need a closer look. Maybe that code implements both DMA and non-DMA modes...

---
DOS gives me freedom to unlimited HW access.

> Maybe here could be some DOS floppy code which does not rely to DMA
> https://github.com/joncampbell123/doslib/tree/master/hw/floppy

Yes, you was right, this supports also noDMA mode, thanks!

I tried to run test.exe and for some reason it detected DMA 2 enabled by default but it can be disabled in the menu. Then I tried seeking and reading a sector but unfortunatelly it was very unreliable (for sure I tried with a floppy that I tested under Linux it reads OK without any errors). Sometimes I got simply "NDMA read failed -2 (d0h)" error and zero data. Sometimes it read a sector but not full. It usually reads a range of 450-510 bytes and it was messed up at first look (the strings in bootsector). Every read attempt got a different number of readed bytes and different content. I also tried to disable interrupt in the menu and tried again but nothing changed, same mess. So this code would do what I need but it's useless for real use. But still may be good as a reference alongside linux floppy driver to learn something from it. It would take some time...

http://rayer.g6.cz/1tmp/fd1.jpg
http://rayer.g6.cz/1tmp/fd2.jpg

EDIT:
This may be the source of problem:
static inline int floppy_controller_wait_data_ready(struct floppy_controller *fdc,unsigned int timeout) {
        do {
                floppy_controller_read_status(fdc);
                if (floppy_controller_data_io_ready(fdc)) return 1;
        } while (--timeout != 0);

This is called in CLI block with value 1000, maybe my PC is too fast :P (limited just by inp I/O speed)

---
DOS gives me freedom to unlimited HW access.