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.

NOT ANY SORTS OF AI WILL BE USED IN THIS PROJECT.

Why ?

People in the 70s got someone on the moon with their brain, and made him come back. AI is useful for medicine, protein research or other deep research subjects. I do not need a LLM to understand and make a computer.

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, not a north and south bridge.

Design

The design is inspired of great people hard work :

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

The core architecture will be inspired of the legendary Intel's MCS-51 microcontroller series.

Core architecture

Made with Drawio.

Registers

Name	Long Name	Description
IR	Instruction Register	Running instruction storage.
A	A Register	ALU first input register.
B	B Register	ALU second input register.
MAR	Memory Address Register	RAM heap access address.
SP	Stack pointer	RAM stack access pointer.

The instruction set.

Every instruction is 1 to 3 bytes long. First is the opcode, and the optionnal 2 bytes are the operands. Operands can be an data (1B), address (1B), or full address (2B).

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

Mnemonic	Description	Pseudocode