[Coco] 6809 disassembly help wanted

[Allen Huffman]

I have our Sub-Etha Software Multiboot code posted to Github now (along with most of the other stuff I have found, even MM/1 items):

https://github.com/allenhuffman/SubEthaSoftware/tree/main/OS-9/MultiBoot

I wrote the OS-9 portion in C, and Terry Todd wrote the assembly code that ran when you typed DOS (loading more code, and presenting a menu of OS-9 Boot Files you could select, then boot from).

I do not have his assembly, but I do have the data that was embedded in my C program which I would write to certain tracks.

I am looking for help in disassembling this code. Jerry “Super Basic” Stratton helped get me started with a perl script he wrote the decodes 6809 op codes.  He also suggested I could POKE them into memory and use a CoCo disassembler. I don’t have one, but I figured out how to use EDTASM’s Z-BUG so sorta do it, and updated the code Mr. Stratton provided until I got something that would compile into the same byte code.

This is on my blog post:

https://subethasoftware.com/2025/11/20/wanted-disassembly-of-sub-etha-softwares-multiboot/

The DOS code uses DSKCON to do “something” but has a random “2” byte in the middle of it, and a BRN (branch never?) and uses memory locations I do not understand.

Terry Todd has gotten deep into how the BASIC ROMs worked and was always giving me POKEs or EXECs to do cool things, so there is no telling what he is patching into ;-)

The second program I haven’t attempted yet, but it should have embedded text strings and such which will make this process trickier for me to figure out.

Any tips?

		- A