The Demon Development Cartridge was an addon from [[John Morrison]].
From his publicity :
The ultimate machine code tool.
Suitable for 464/664 and 6128 machines.
Demon will give you a full control of your Amstrad.
Stop any program, any time by a press of a buttom.
The memrory remains intact and can be :
- Saved to Tape/Disc.
- Debugged.
- Traced.
- Moved.
- Disassembled.
- Etc.
Now, thanks to Jose Leandro, the hardware specialist of the spectrum, with his famous page :