Multi Mark – For Stubborn 3″ Disks

MuckyPaws February 10, 2021 Leave a Comment

I’ve been slowly selling off my retro gear for a while… I don’t use it, except for archiving off my old source code for hacking projects back in the day. There’s plenty of collectors out there that are preserving these antiques and giving them a loving home…

I had over Three Hundred – Three Inch – Amstrad CPC Disks of which most were sold off to raise funds for a charity close to my heart. Towards late last year, I found the need for more of these special disks than I’d allowed for, and bought a bunch from a reputable seller known on the retro scene.

Only this evening have I tried to do anything with them. I ran a couple of disks through Grease Weazle to check their integrity, and sadly it seems they’ve not survived the decades particularly well. I attempted a Magnetic Flux write to the disks to see if that could resolve the numerous CRC errors identified on many of the sectors… Nothing… I attempted another low level write using Discology, it seems these disks are destined for recycling.

Back in the day, I would have quickly written in assembler a disk formatting talking directly with the μPD765a Disk Controller and marked the troublesome sectors as taken in the disk catalog, making the disk at least useable. If you’re interested in my old source code, it can be found on my GitHub Repo here: https://github.com/muckypaws/AmstradCPC/blob/master/Assembly/DDFDC/DDFDC_MK2.asm

That said, Shaun M Neary who runs an active Amstrad CPC Group suggested a tool called Multi-Mark http://www.genesis8bit.fr/frontend/disk.php, written by Tom and Jerry of GPA and is basically a much more elegant solution than one I’d hacked together previously back in the day. Giving you a simple to use graphical interface, RSX Commands and a ROM file if you have an EEPROM Programmer or one of the Duke’s M4 Boards which allows WiFi, Programmable ROM Slots and Storage. https://www.spinpoint.org/2019/11/19/m4-board-guides/ and I’ll cover the M4 off in a later article.

Using HXC and Greaseweasle, I converted to the DSK Image to HFE by Loading the DSK and Exporting as HFE before writing HFE image to physical disk via GreaseWeasle using the following: –

gw write --drive B --track="c=0-41:h=0" "./Multi Mark 1_2a_dsk.hfe"

Once powered on the CPC, inserted the disk, I could fire the tool up using the RUN”MML-12″ command and away we go…

Multi-Mark 1.2 is featured packed allowing you to easily verify and format disks, you can also play around the XPB (Extended Disk Parameter Block) if you’re looking to create more specialist formats, and even modify the GAP#3 byte if you’re really into low level disk formats! As a side note, I used to mess around with GAP#3 and other parameters when creating disk protection systems since the original hardware was unable to copy these exactly (Hardware Disk Duplicators had no problem since their firmware was modified).

An example of one of my Disk protection systems can be found here: https://github.com/muckypaws/AmstradCPC/blob/master/Assembly/Jacelock/Jacelock.asm

The format tool, attempts a format of the disk, and verifies each track and sector, making a note of any failures. A file is then written to the disks catalog marking invalid sectors as used, thus leaving the remaining good sectors available. That said, any failing disk should be replaced ASAP. File sizes of the bad sectors ranged from 1K to 65K on one of the worst disks.