The Acorn Microcomputer

The lower board is the Acorn Microcomputer proper:

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It holds (from left to right, top row):

• National Semiconductor INS8154N RAM/IO chip (128 bytes RAM plus receivers and drivers for display and keyboard)
• MOS Technologies MPS6502 Microprocessor [0279]
• Two 2114 static RAM chips (each 1024x4-bit, 1KiloByte total)
• Two 74S571 PROM chips (each 512x4-bit, 512 Bytes total)
• Sockets for additional PROM and RAM/IO chips
• Pads for a EuroConnector.

Along the bottom are sites for interrupt switches (NMI, RST, IRQ), the 1.006MHz crystal, circuitry for address decoding and chip selection, and (at the bottom right) an LM340T5 5-Volt regulator. The board was also marketed as a ‘Single Board Controller’ without the RAM and ROM chips.