how to create a valid MyDOS partition?

[TheMontezuma]

1 hour ago, Larry said:

What board are you using to provide 90-degree use of the IDE+2?  Is there a memory expansion in there, and if so, did you try without the 90-degree adapter?  Probably a silly question, but did you clean the ECI contacts?  I've had trouble with that before.  And you might run drac030's RW-CRC to test the validity of the connection and card.  I've run into the "off by one" issue with several of Puff's software, most notably VTOCFIX.  I've always found it to be harmless.  You also might try drac030's original FDISK.COM.  Although IIRC, you can't use it with the more recent bios versions.  I think I'm still on 1.4, but have my Black Box hooked up ATM.  

It is just a photo I had at hand, but I performed all the tests with IDE 2 directly inserted in the computer.

BTW:

After I successfully setup MyDOS partitions:

 

 

The MIDICar Player:

https://github.com/GSoftwareDevelopment/MIDICar-Player

can be used not only with MIDICar, but also with MIDIMate modules.

Until now I used it with SDX, but I was very curious if it also works with MyDOS.

 

Edited October 29, 2023 by TheMontezuma

[+CharlieChaplin]

Afair, pancio released updates of MCP in the Abbuc forum, unsure if the latest version now works under MyDOS or still does not work. (Don't have the MidiCar hardware yet.)

 

And as always, if I go to the github link, I see dozens of sources and subdirs there, but cannot find any ATR's for download. But maybe there is a newer version available at github and I am too blind to see / find it.  (I would prefer that programmers also create a subdir at sourceforge, github, ..., named ATR or XEX where the executable software for the A8 can be downloaded.)

 

But we are offtopic here... sorry. Downloads of the MCP software can now be found here:

 

 

 

[drac030]

1 hour ago, flashjazzcat said:

Multiple logical sectors are not packed into physical sectors, so 65535 is indeed the correct number regardless of the sector size (65535 sectors at 256 bytes each will result in a 16MB partition, albeit 256 bytes short of that since there's no sector 0).

Hmm. Are you sure of this? This is the partition table from my Altirra setup. The entry with red underscores is the partition I created (or rather: tried to create) yesterday:

 

 

Status $42 means "metadata sector present, 256 bytes per logical sector". And the size field, which per specification should contain "Sector count (number of physical sectors occupied by partition)", has a value of $0000FFFF = 65535 "physical" sectors, i.e. 512-byters = 32 MB. Am I missing something?

 

By the way, this is the exact partiton table FDISK 4.85 keeps destroying. This looks like a bug.

Edited October 29, 2023 by drac030

[flashjazzcat]

I'm probably mistaken, since I've been completely immersed in DIY at our new house for over two months and haven't touched any Atari software in that time. Likely there is a bug, but if you could ZIP down the APT in question and post/send it, it would certainly aid me in troubleshooting any problems in software whose source code I haven't looked at in a considerable length of time. Debugging and typing aren't easy since I have a tendon injury in my right hand (which is splinted up; I didn't sustain the injury while doing DIY, but while scrubbing a carpet), but I'll be more than happy to try and iron out these issues as soon as I get a chance.

[drac030]

1 hour ago, flashjazzcat said:

I'm probably mistaken, since I've been completely immersed in DIY at our new house for over two months and haven't touched any Atari software in that time. Likely there is a bug, but if you could ZIP down the APT in question and post/send it, it would certainly aid me in troubleshooting any problems in software whose source code I haven't looked at in a considerable length of time. Debugging and typing aren't easy since I have a tendon injury in my right hand (which is splinted up; I didn't sustain the injury while doing DIY, but while scrubbing a carpet), but I'll be more than happy to try and iron out these issues as soon as I get a chance.

Ok, here it is:

 

fdisk_bug.zip

 

1) 00000000.MBR - MBR prior to being screwed.

2) 000E003F.APT - the APT partition table apparently causing the issue. The numbers in both filenames are LBA sector numbers (as you can guess).

3) fdisk_16_partitions.png - a snapshot of FDISK partition list prior to the trouble.

4) fdisk_after.png - a snapshort of Eddy presenting the contents of the first half of sector 0 (i.e. the MBR) afterwards. The other half is not visible, but it contains all zeros anyways.

5) mbrview - a small tool I put up today to list the MBR entries in human readable form.

 

Observations:

 

a) To trigger the issue it is enough to open the partition list in FDISK, then write the partition table out, without touching anything.

b) but otherwise, when changing settings, any required operations on the APT itself seem to be performed correctly, and APT itself does not seem damaged in any way.

c) the only victim is the MBR, which gets overwritten with garbage, being actually some form of APT header in its first 16 bytes, and all zeros besides.

d) the red line on the snapshot is the header field "Previous sector in the sector chain" and it points to the actual APT sector, which seems rather odd.

 

I am not sure if the MBR here is 100% correct, because I have restored it manually. It works, though.

 

PS. I looked at the code and you are right, the logical sectors are not packed, I must have confused that with the older version (i.e. KMK/JŻ IDE), where there were 2 logical sectors stored per one physical.

Edited October 29, 2023 by drac030
typos

[flashjazzcat]

Thanks so much - I appreciate it. It's quite frightening to me that I can't provide a definite answer regarding sector packing without recourse to the source code (which I am nowhere near at the moment). I can only put it down to age.

 

Thanks again, anyway. Perhaps I'll have a look at this tonight.

 

PS: Now the mists of confusion clear, indeed logical sectors are simply padded with 0 using various interleave schemes.

Edited October 29, 2023 by flashjazzcat