Appendix V: Building and Booting a ROM

The steps from S5, for reference.

Once: make a folder for your MOS, put mos12.asm in it, and unpack the original ROMs there:

unzip ~/roms/einstein.zip

(using the path to your own einstein.zip). That gives mos12.i023 and mos121.i023. Leave the original zip untouched.

Each time you change the source:

z80asm -i mos12.asm -o mos12.i023
zip einstein.zip mos12.i023 mos121.i023
mame einstein -rompath . -window

Checks:

• mos12.i023 must be exactly 8,192 bytes. If you add code, remove the same number of unused FFh bytes from the end (S15).
• Unchanged source gives the original ROM, and MAME starts without complaint.
• Changed source makes MAME warn WRONG CHECKSUMS and then run your ROM.
• To run the original Einstein again, start MAME without -rompath ..
• On a real Einstein, the image must be programmed into an 8K EPROM fitted in place of the MOS ROM: Appendix VI.