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intric8
Seattle, WA, USA

Posted Tue Feb 21, 2023 9:35 am

Last month as I was in the throes of my MSD SD-2 project, I'd also been working to better understand the capabilities of the Commodore IEC chain. I thought I'd read somewhere that Commodore's 8-bit machines could use up to 8 drives at a time (because) and was working on a wacky setup of my own.

I decided to attempt to hook up the following:
  • C128D with 1571 (Device ID 8)
  • MSD SD-2 (9)
  • RAMLink (16 - its default ID)
  • CMD HD (12 - its default ID)
  • and 1581 (10)
IMG_1385.jpg
You can see 4 of the 5 devices here. The 5th, the RAMLink, is behind the computer in the cartridge slot.


But for some reason, the 1581 at ID 10 wouldn’t work. It would hang on any kind of disk read. Every. Time.

I then began to ponder if the order in which things were attached in the chain mattered. I also tried with a different 1581 and got the same results.

As it goes, a lot of plugging and unplugging commenced. When I removed the RAMLink and CMD HD from the chain, voila! Everything was fine. And then, I figured it out. This was my first experience ever using a CMD parallel cable, and I wasn’t sure how the serial chain would work.

In order to get this all working I had to do it like this:
diagram.png
The bottom line is I couldn't attach any serial devices to the back of the CMD HD since it was being connected to the computer via parallel cable. It was essentially it's own orphaned culdesac. If I tried to attach a serial device to the back of the HD (it has 2 ports) those devices would get very confused. As long as I chained them up separately all on their own IEC-only lines it worked perfectly.

That does make me wonder if you can have more than one CMD HD HDD attached via parallel, and if so, how? That being said I would never need this - my HD is a ridiculous 2GB drive! It was more just a curiosity of mine trying to figure out how it might come together in a theoretical puzzle.

(In this current setup I can also easily swap the 8/9 IDs between the C128D and MSD SD-2, as the MSD-SD-2 software often wants to be on ID 8 .)





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