Computer

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Summary

1. Aims and challenges
2. Architecture choices
3. Design
   1. The instruction set.

Aims and challenges

Make a turing complete computer from scratch.

The computer will be composed of :

• A CPU
• Some RAM
• Some ROM

At first every part will be the "industrial" version :

• The CPU from logic gates.
• The RAM a SRAM chip (UM61256BK-20 from 1993)
• The ROM another chip (D27C010 from 1986 !)

Then the aim is to replace them with made from scratch versions. For the moment only the RAM is meant to be replaced with homemade magnetic core RAM.

Architecture choices

The computer will be in 8 bits since the RAM and ROM are meant to be in 8 bits. The CPU will have ports for inputs / outputs.

Design

The design is inspired of great people hard work :

• Ben Eater's 8 bits breadboard computer
• Mattbatwings's minecraft computer tutorial

The instruction set.

Every instruction is 8 bits long. And there is 3 bytes of data after the instruction. Because the ROM is 8 bits, every instruction will take 4 bytes. This property might help for instruction pipelining in the future.

These are only real instructions. Pseudoinstruction will be defined later.

Mnemonic	Description	Pseudocode