General Category > Programming

Unassembled CPC6128 Firmware Now Available

<< < (2/3) > >>

Bread80:

And the BASIC is now uploaded https://github.com/Bread80/Amstrad-CPC-BASIC-Source


There's still much reverse engineering to do, mostly around the memory management and string handling stuff (also memory management  ;) ).


And you can't really expand it because there's no spare bytes in the ROM. So I'd like to split it across two ROMs, which means a lot of disentangling of command prompt and run-time code. But if you want so how BASIC does it's thing then it's worth a look, and I'd added quite a few notes in the readme to guide you.

pelrun:
No spare bytes in the rom? What about that block of rst 0's hiding at the end of Errors.asm?  ;D

Bread80:
Well, yes. I'm not entirely sure if they're there for a reason I've not discovered and they'll break something if I remove them, or if they're just padding so they could say they've filled up the ROM and claim their paycheck  ;D

pelrun:
If it was filled with literally anything other than the "single byte reset" opcode, I'd agree. But it's the smartest choice for a byte to fill unused ROM space on the CPC, rather than 0x00 (which would act as a NOP-sled, executing whatever random code/data was at the end of the block) or 0xFF (which looks like RST #38, jumping to the interrupt vector instead.)
Any buggy code which manages to jump to that block will immediately reset the machine back to a good state.

zhulien:

--- Quote from: pelrun on 05:37, 01 November 21 ---No spare bytes in the rom? What about that block of rst 0's hiding at the end of Errors.asm?  ;D

--- End quote ---


If you boot with Amstrad brand, you can likely use those other brand bytes. 

Navigation

[0] Message Index

[#] Next page

[*] Previous page

Go to full version
Powered by SMFPacks Reactions Mod
Powered by SMFPacks Alerts Pro Mod
Powered by SMFPacks Mentions Pro Mod