One of the selling points of systems from The Digital Group is that you had a choice of CPUs. The most common choice was the Zilog Z-80, but there were also CPU boards with the Intel 8080, Motorola 6800, and MOS Technology 6502.
But the first CPU MOS Technology produced in the 65xx family was the 6501. It was completely pin-compatible with the Motorola 6800.
The Digital Group\'s 6800 board was designed to support either the 6800/6501 or the 6502 with only minor changes.