Spec256 is a 2000s format where artists recoloured Spectrum games into eight extra bit-planes, and a second "graphical" Z80 propagates those colours through the game's own drawing routines. On the FPGA that is one master Z80 plus eight graphical lanes in lockstep.

The first moving Jetpac exposed a real bug, the lanes picking up DD/FD prefixes one fetch late, caught by comparing 72,000 instructions against the GZX emulator. After the fix: clean enhanced Jetpac and Chuckie Egg, with game packs loaded at runtime over a UART without reprogramming the FPGA.