Build An 8-Bit Computer by Ben Eater (Part 3) - Random Access Memory (RAM) Module and Program Counter

Build An 8-Bit Computer by Ben Eater - Random Access Memory (RAM) Module and Program Counter (Kit 3 of 4)

In this kit, the random access memory (RAM) stores the program the computer is executing as well as any data the program needs. Our breadboard computer uses 4-bit addresses which means it will only have 16 bytes of RAM, thus limiting the size and complexity of the programs it can run. This is by far its biggest limitation. See the build videos below.

The other part of the build is the program counter (PC) which counts in binary to keep track of which instruction the computer is currently executing. See below for the videos explaining how counting in binary works. Then follow the Program Counter build videos, also below.

Kit Includes:

Resources & Downloads

• 74LS00 Quad NAND gate datasheet (.pdf)
• 74LS04 Hex inverter datasheet (.pdf)
• 74LS157 Quad 2-to-1 selectors/multiplexer datasheet (.pdf)
• 74LS173 4-bit D register datasheets (.pdf)
• 74189 64-bit RAM datasheet (.pdf)
• 74LS245 8-bit bus transceiver datasheet (.pdf)
• 74LS161 4-bit binary counter datasheet (.pdf)
• About the author, Ben Eater
• Eater.net (off-site)
• Sub reddit for Ben Eater (off-site)

RAM Videos

Program Counter Theory

Program Counter Design and Build

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