VOGONS

Mounting a 320KB DOS image: an impossible task

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First post, by olifiers

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Hi there! Old lurker now in need of help!

I'm in the (long) process of reviving a Dynalogic Hyperion computer which has thrown everything at me while resisting the effort: flamed PSU, water damaged logic board, fried CRT, you name it. One step at a time I am prevaling, and now seems like the last hurdle is its character generator logic is borked, as I can get graphics to show, but no characters at all.

So, the question in question! I've got a Hyperion diagnostics .IMD 320KB floppy image I can successfully burn into a 5 1/4 using a GreaseWeazle and boot the Hyperion with it. But I need to modify this image's content, and it seems truly impossible to mount or edit a 320KB DOS image on Windows no matter what I try.

Things I've tried:
- Read the floppy back into a .IMG GreaseWeazle image (doesn't mount on DosBox);
- Tried converting using libdsk's dsktrans (it errors out with a 'Reading: No Data');
- Converted using HxCFloppyEmulator (converts but doesn't mount on DosBox);
- Tried converting into 360KB with WinImage (doesn't open either the IMD or the IMG).

I've tried mounting it on DosBox 'imgmount'using both '-t floppy' (mounts but no content is shown) and '-size 512,8,2,40' (crashes)

I'm now out of ideas, so screaming for help: Anyone have a good solution to convert this 320KB IMD into something I can mount on DosBox or Windows or anything in order to edit it and put it back into the floppy for debugging the Hyperion further?

I'm attaching the .IMD below and a picture of the Hyperion coming to life after such a looooong marathon of replacing caps, fuses, DB25s, NPNs and even an oscillator... 😁

Thanks in advance!!!

Reply 1 of 6, by weedeewee

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I can't offer much help, but from a quick look at the image. It doesn't look like a normal dos formatted floppy.
The bootsector should end with 55 AA or vice versa, if i'm not mistaken and in your image it doesn't.
All I can guess from this is that, oh wait, no the fact that IMD added some stuff just makes it a little more offset but it's still not where I'm expecting it, the layout of your disk is not a normal dos formatted layout.

edit: seems like i was wrong.

Last edited by weedeewee on 2025-03-02, 20:03. Edited 1 time in total.

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Reply 2 of 6, by megatron-uk

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$ mdir -i hyp.raw
Volume in drive : has no label
Directory for ::/

COMMAND COM 14830 1983-10-26 11:05
SPEAKER EXE 2048 1983-03-15 1:20
CHARSET EXE 4736 1982-12-20 0:47
LOWRES COM 48 1982-12-20 0:08
HIGHRES COM 40 1982-12-20 0:03
DISKTEST EXE 14464 1983-03-03 9:05
RAMTEST EXE 11264 1983-01-04 8:49
CRTRAM EXE 10880 1980-01-01 2:43
PARALLEL COM 770 1980-01-01 0:15
SERIAL COM 811 1982-12-20 12:29
MODEM COM 650 1982-12-20 0:18
DTMF COM 616 1982-12-20 0:27
ATTRIBUT EXE 3072 1980-01-01 0:31
AUTOEXEC BAK 92 2002-10-19 0:00
CRT BAS 8960 1983-09-01 13:53
SQUARE70 EXE 2688 1980-01-01 0:07
SQUARE60 EXE 2688 1980-01-01 0:43
BASICA EXE 56832 1983-03-16 11:06
LINEARIT EXE 4736 1980-01-01 0:04
MODE COM 30168 1983-05-03 15:34
BRIGHTNE EXE 4096 1982-11-10 0:00
AUTOEXEC BAT 84 1983-09-09 11:33
22 files 174 573 bytes
110 592 bytes free

I unzipped the image, converted it from IMD to raw sector format with SAMDisk (https://simonowen.com/samdisk/), and it opens/reads/dir/cp/del just fine with Linux mtools (which works on standard FAT format floppies).

My collection database and technical wiki:
https://www.target-earth.net

Reply 3 of 6, by megatron-uk

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Files copy into the image just fine:

$ touch VOGONS.TXT
$ mcopy -i hyp.raw VOGONS.TXT ::/
$ mdir -i hyp.raw
Volume in drive : has no label
Directory for ::/

COMMAND COM 14830 1983-10-26 11:05
SPEAKER EXE 2048 1983-03-15 1:20
CHARSET EXE 4736 1982-12-20 0:47
LOWRES COM 48 1982-12-20 0:08
HIGHRES COM 40 1982-12-20 0:03
DISKTEST EXE 14464 1983-03-03 9:05
RAMTEST EXE 11264 1983-01-04 8:49
CRTRAM EXE 10880 1980-01-01 2:43
PARALLEL COM 770 1980-01-01 0:15
SERIAL COM 811 1982-12-20 12:29
MODEM COM 650 1982-12-20 0:18
DTMF COM 616 1982-12-20 0:27
ATTRIBUT EXE 3072 1980-01-01 0:31
AUTOEXEC BAK 92 2002-10-19 0:00
CRT BAS 8960 1983-09-01 13:53
SQUARE70 EXE 2688 1980-01-01 0:07
SQUARE60 EXE 2688 1980-01-01 0:43
BASICA EXE 56832 1983-03-16 11:06
LINEARIT EXE 4736 1980-01-01 0:04
MODE COM 30168 1983-05-03 15:34
BRIGHTNE EXE 4096 1982-11-10 0:00
AUTOEXEC BAT 84 1983-09-09 11:33
VOGONS TXT 0 2025-03-02 19:49
23 files 174 573 bytes
110 592 bytes free
$

My collection database and technical wiki:
https://www.target-earth.net

Reply 4 of 6, by megatron-uk

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What mods do you need to make to the image? A raw sector image should write back to a physical floppy absolutely fine.

My collection database and technical wiki:
https://www.target-earth.net

Reply 5 of 6, by olifiers

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megatron-uk wrote on 2025-03-02, 19:52:

What mods do you need to make to the image? A raw sector image should write back to a physical floppy absolutely fine.

Suuuuper thanks, megatron -- this is exactly what I needed. Getting familiar with both Samdisk and mtools, but I'm already copying files from and to the .raw image. Excellent outcome!

Owe you a pint, dear sir!!!

Reply 6 of 6, by megatron-uk

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Not a problem!

My collection database and technical wiki:
https://www.target-earth.net

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