Memory

Required: 11 × 1024 bits of static RAM. Here's the circuit (also known as Master Loop Block 5). The 74260 (dual five input NOR gate) and 7400 are used to detect if b is not equal to zero.

Realised using eleven Intel DIL2125AL 1024 bit static RAM chips, date coded  September 1979; 74214 chips seem impossible to find - presumably they had a very short production run, but the DIL2125s have the same pin outs and are TTL compatible and single 5 V supply. And they are 'low operating power'...just 0.39 mW/Bit(!). 

Note from construction diary: RAM chips slightly warm to the touch!

Current consumption (526 - 587 mA) depends on the address, and whether reading or writing (and not because of the LEDs). Interesting.

Chip count:

11 × DIL2125AL-2 (1024-bit static RAM)

2 × 74245 (octal bus transceiver)

1 × 7400 (quad NAND gate)

1 × 74260 (dual five input NOR gate)

plus LEDs for diagnostics. The hexadecimal displays were omitted from the final build; I think the LEDs suffice.