abaffa / sol-1

Sol-1 Homebrew Minicomputer

Sol-1 is a homebrew CPU and Minicomputer built from 74HC logic.

Features

Hardware

• User and Kernel priviledge modes, with up to 256 processes running in parallel.

• Paged virtual memory, such that each process can have a total of 64KB RAM for itself.

• Two serial ports (16550), a real time clock(M48T02), 2 parallel ports(8255), a programmable timer(8253), an IDE hard-drive interface(2.5 Inch HDD), and a soundboard(AY-3-8910).

• 8 prioritized external interrupts

• DMA channel

• The sequencer is microcoded, with 15 ROMS operating horizontally

• 8/16-Bit MUL and DIV instructions

• Fast indexed string instructions in the spirit of x86’s REP MOVSB, CMPSB, LODSB, STOSB, etc

Register Table

General Purpose Registers

16bit	8bit	Description
A	AH/AL	Accumulator
B	BH/BL	Base Register (Secondary Counter Register)
C	CH/CL	Counter Register (Primary Counter)
D	DH/DL	Data Register / Data Pointer
G	GH/GL	General Register (For scratch)

Special Purpose Registers

16bit	8bit	Description
PC		Program Counter
SP		Stack Pointer
SSP		Supervisor Stack Pointer
BP		Base Pointer (Used to manage stack frames)
SI		Source Index (Source address for string operations)
DI		Destination Index (Destination address for string operations)
PTB		Page Table Base
Status		CPU Status
Flags		Arithmetic and Logic flags register
TDR	TDRH/TDRL	Temporary Data Register (Internal CPU scratch register)

Software

• Unix-like operating system (in progress and very early)

• C compiler that generates a Sol-1 assembly output file (The output assembly is then assembled separately.)

• SystemVerilog model

Video demonstrations here