Motorola MC68000 (second-source parts common)
About this component
The 68000 runs game code from the cartridge and works with 64 KB of work RAM, the VDP and, through the bus arbiter, the Z80 side. Model 1 boards use a through-hole DIP-64 part that can come from several second-source makers, all interchangeable. In the last Model 2 and the Genesis 3 there is no separate 68000; it is merged into a single ASIC. A missing clock or a stuck bus line from a failed RAM or arbiter can look like a dead CPU, so check those first. Part variants: Model 1 boards carry second-source 68000s in DIP-64: a VA2 US board used a Signetics SCN68000C8N64; Hitachi and Motorola parts also appear (VA5 had Signetics earlier, Motorola on 1991 boards). VA7 Model 1 uses a Motorola part in PLCC. On Model 2 VA4 and Genesis 3 the 68000 is inside the 315-5960 / 315-6123 'Genesis on a chip' ASIC.
16/32-bit 68000 CPU @7.6MHz.
Pinout & readings
No pinout or reference readings yet — these show what each pin does and what a healthy part should measure. Check the datasheet meanwhile.