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Nabu - trying to fix a problem in my FD bootloader

usotsuki

usotsuki

Experienced Member
Joined
Nov 30, 2010
Messages
85
This is certainly a case of "coder is an ID10T", but last July I tried to write a floppy disk bootloader for the Nabu that:
  1. Doesn't use the official code, because I want it copyright-clean.
  2. Can boot existing CP/M 3.1 boot disks.
I coded it in two forms - one that is part of my boot ROM project, and one that can be chainloaded from the modem emulators (thus, no need to replace the ROM to boot a floppy; since the original firmware can't do this). But somehow I did a stupid, and it only works on MAME, if at all. I have no idea what I'm doing even after reading TFM.

After some time trying to figure out what might even be wrong, I gave up and let it sit for some time; now that I've actually managed to get some real software (the game "Lode Runner", ported from MSX) up on the system, and now that I'm involved in an unrelated homebrew hardware project, I'd like to try to figure it out at last.

Didn't know where else to post this, but it's specifically related to booting CP/M-80, so I figured it was apropos to this section.

ETA: This is based on an FD-1797, and I know the port addresses. I think at least some of them are documented in my code. https://github.com/buricco/opennabuipl/
 
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To be fair, there's Patched ROM 14, which provides the same things I'm providing. And the Nabu company's been dead for decades. But there's always a successor in interest and I'd prefer to take the safe approach rather than suddenly have some megacorp that bought out some other megacorp that bought out some other megacorp in the 80s come out of nowhere and sue me for everything I'm worth. Plus, like I said, cutting it down to something that will boot a floppy and loads from the modem would be a useful thing (even though I have the ability to burn EPROMs now).

I'm way out of my league here.
 
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