In order to initialize the LEDs and other chips, the CPU needs to be running properly,
which requires a good CPU, clock, and CPU reset, plus the EPROMs that hold the
CPU code need to have the correct data and be connected properly to the address
and data buses. Also, the SRAM chips need to be working and connected properly
as well. So a lot of chips are involved in having the CPU execute code properly,
including some small support logic chips.

Bob