MiniMig with AGA

[aperez]

A Keyrah is hideously overpriced. The Custom-looking Motorola MPU which is on the A1200 used a bog-standard Motorola 68HC05 MCU.

See http://www.amiga-stuff.com/hardware/68hc05.html for more info.

[aperez]

In this case, the microcontroller in question can be had for £2.08  

See http://uk.farnell.com/freescale-semiconductor/mc68hc705j1acpe/8bit-mcu-68hc705-dip20/dp/1200547 in the UK

These can also be purchase directly from Digikey in the US for $4/ea. See http://parts.digikey.com/1/parts/1081847-ic-mcu-4mhz-1-2k-otp-20-dip-mc68hc705j1acpe.html

Whether or not the contents of the (typically flash EEPROM) could be read back is another matter.

The 68HC05C9A that Commodore employed had a mask ROM area, where their code lived. The closest part number to it is http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=68HC05C9A