Multicomp in a Box

Grant Searle's FPGA MultiComp Project

FPGA Recreations of 6502, 6809, Z80, and Z80 Vintage Computers

• Multicomp on Land Boards Cards - Hardware
• Multicomp on Purchased Cards
• FPGA Support Cards
• MultiComp Wiki Page on GitHub
• Multicomp Github repo

Other Links

• Grant Searle's Multicomp page
• Neal Crook's 6809 Multicomp Github
• Retrobrewing Multicomp
• mc-2g-1024 multi-boot capability
• System 09 - VHDL 6809 System On a Chip
• Multicomp build on Cyclone IV

Our MultiComp Retro-Computer Video Series

Cyclone II Video Series

Video Series

Cyclone IV Video Series

Video Series

6800 CPU

S120 Bus Computer

My first attempt to build a computer was around an MC6800 CPU so it has a soft spot in my heart, Back in 1977 (before my Ohio Scientific SuperBoard II I had my own homebrew computer. I never took any pictures of it and the hardware is long gone now. These are the pieces of it I remember.

• Ran on Elco? 120 pin edge connector wire wrapped cards
• 6800 Processor board running at 1 MHz
• 2K of Static RAM board
• 2716 EEPROM board (may have had 4 sockets total, don't recall for sure)
• Front panel switches and LEDs to enter the address/data (Step/Insert) and blink lights

I remember getting it to run and I do remember blinking a light back and forth on it. Once I got the SuperBoard II, I stopped working on my own board.

It might be fun to reproduce that board!

Pieces to Reproduce my original S120 Bus Computer

• Michael Holley's SWTPC 6800/6809 documentation collection
• N8VEM RetroComputing Wikipedia page
• Retrobrew Computers
• Kim-1 board - Similar concept

Hardware

• M6800 VHDL code from OpenCores

Software

• AS68 Cross Assembler
• ASM68C Cross Assembler
• Collection of Assembly Language tools for the M6800
• 6800 Basics
• 6800 Assembly Language Programming (pdf) by Lance Leventhal
• 6800 Instruction Set Cheat Sheet

M6800_MIKBUG - Tested/Works

This is an FPGA build of something similar to that machine

• Fills a hole in Grant Searle's Multicomp (he hadn't finished a 6800 version)
  • Runs Tom Pittman's Tiny BASIC
• MC6800 CPU
• Running MIKBUG from back in the day (SmithBug ACIA version)
• 12.5 MHz
• 60K (external) RAM version
• MC6850 ACIA UART
• Video Display Unit (VDU)
  • Color attributes
  • XGA 80x25 ANSI character display
  • Extended (256) character set
• PS/2 keyboard

Memory Map

• $0000-$EFFF - 60KB external sRAM
  • $0000-$EEFF - User RAM area
  • $EF00-$EFFF - scratchpad used by MIKBUG
• I/O Map
  • $FC18-$FC19 - VDU
  • $FC28-$FC29 - ACIA
    • • Pin_60 of the FPGA swaps addresses of VDU and ACIA port
      • Installed (Pin_60 to Ground) uses Serial port
      • Removed uses VDU
• $F000-$FFFF - MIKBUG ROM
  • I/O "hole" opened up at 0xFC00-0xFCFF

Systems

• MITS Altair 680
• Altair 680b Mainframe
• SWTPC 6800
• SWTP 6800 system
• Sphere 1 computer History
• DREAM 6800 Archive Site
• Planet m68k - News around Motorola 68000 CPU computer systems

Software

• Muticomp M6800 MIKBUG
• Smithbug, MIKBUG 6800 ROM monitor
• Monitors for the 6800
• A68 6800 cross-assembler
• MC6800 Assembler
• TSC BASIC for SWTPc 6800
• 6800 Assembly language books
• SWTPC 6800 Resident Assembler MP-E - (YouTube)
• EXORsim - Motorola EXORciser Simulator

Z80 CPU

• Land Boards Z80 in 3 Chips
• Hackaday Z80 in 3 Chips
  • 512KB SRAM
• rhkoolstar sbc-2g-512 - SD card image
  • Archive of rhkoolstar sbc-2g-512

Stackup (top to bottom)

• Front Panel For 8 Bit Computers
• Z80 in 3 Chips
• SD_CARD_X49 mounted on CARRIER95TO49MM
• JOYPAD

Z80-MBC2 Build

Z80-MBC2 Build Notes

CP/M on FPGA - by Grant Searle

• Archive.org copy of Grant's site from 2012
• Archive.org copy of Grant's Multicomp from 2012
• Fit results (EP2C5 FPGA)
  • Two UART Serial interface
  • No Video Display
  • External RAM

• Grant noted about the SD card interface:

... the SD controller is easy to control - in BASIC POKE the sector number, POKE the write command, 
POKE 512 bytes to the same location to write a sector, 
or POKE the sector number, POKE the read command, and PEEK 512 bytes to read a sector.

Retrobrew Multi-boot Multicomp Computer Builds

• MultiComputerZ80 build - Lots of extras - mc-2g-1024 Help file
• Multicomp Z80 with b/w Graphics - muellerk page
• mc-2g-1024 Image18 - Multiboot SD card

mc-2g-1024 Images

• Copy image System18.img to your SD-card. Use direct imaging software (dd in Linux, Win32DiskImager in Windows). Copy to the start of the card
  • rhkoolstar mc-2g-1024 is backed up here
• Included OSs are
  • Type Snnn to select OS at multiboot
  • S001 - Dos+ 2.5 Copyright 1986 (c) by C.B. Falconer, CCP+ Ver. 2.2 (CP/M 2.2 compatible)
  • S002 - CP/M 2.2 (c) 1979 by Digital Research
  • S003 - CP/M Version 3.0 BIOS (2016/9/13)
    • CP/M Version 3.0 Operating System System Guide
  • S004 - MP/M II V2.1
  • S005 - Z80 BASIC Ver 4.7b, Copyright (C) 1978 by Microsoft
  • S006 - ZSDOS v1.1 (c) 1986-8 Harold F. Bower & Cameron W. Cotrill, ZCPR2 (c) 1982 by Richard Conn (CP/M 2.2 compatible)
  • S007 - ZCPR compatible system for CP/M+ (CP/M 3.0) by Simeon Cran

• Additional Volumes
  • Inspired by mc-2g-1024 original but modified
  • Sources from here
  • Mount using mount d vol
    • Ex: mount b: 9 will mount ZCPR3 Utilities A-O as drive b:
  • Volume.008 - ?
  • Volume.009 - ZCPR3 Utilities A-O
  • Volume.010 - ZCPR3 Utilities P-Z
  • Volume.011 - Wordstar, DBase, SuperCal
  • Volume.012 - Games
  • Volume.013 - MuMath
  • Volume.014 - Documentation
  • Volume.015 - Languages (TurboPascal, Fortran, BBC BASIC)
  • Volume.016 - Languages (Algol, Aztec C, APL, PLI, FORTH)
  • Volume.017 - Languages (BDS Tiny C, Janis Ada15, MS COBOL, PILOT)
  • Volume.018-253 - User volumes

Retrobrew Computer Builds of the Multicomp Project(s)

• Multi-boot Multicomp build by muellerk builds on Multi-boot Multicomp build by rhkoolstar
• Some folks made a MultiComputer PCB, too - Retrobrewing
• Another board
• Yet another board
• Jeelabs Building a MultiComp-based Z80
• Patch WordStar 3.0 to use ANSI screen commands
• Homebrew Z80
• "The Thing": FPGA + STM32

CP/M Notes

• CP/M is not case sensitive
• REN NEWNAME.EXT=OLDNAME.EXT - Rename a file from the old to the new name
• ERA FILE2ERA.EXT - Erase a file
• Asterisk is wildcard
• .COM are command files
• PIP/PPIP - copy command (CP/M 2.2, CP/M 3)
  • CP/M 2.2 uses PIP
  • PIP NEWCOPY.EXT=COPYFROM.EXT - Copy from COPYFROM.EXT to NEWCOPY.EXT
  • CP/M 3 uses PPIP
• Drive references A:
  • Drives go from A-???
• LS is a better directory program

CP/M Resources on the Net

• CP/M Operating System Manual
• Digital Research CP/M Site
• A Short History of CP/M
• CP/M Internals
• CP/M Console Command Processor Instructions
• OAK Repository - CP/M Archive - On the Wayback machine
• Intro to Z80 Retrocomputing - Scott Baker's series on the RC2014
• Digital Research Source Code
• CP/M Programming Languages and Tools retroarchive page
  • retroarchive page - mirror
• Multicomp FPGA - CP/M Demo Disk
• BBC BASIC (Z80)
  • BBC BASIC (Z80) Manual

*BYE- Return to CP/M

• Altair downloads

Z80 Software Development

AZTEC C Compiler

• Compile C code to CP/M executable
• Aztec C Compiler Manual
  • C Vers. 1.06D 8080 (C) 1982 1983 1984 by Manx Software Systems
• Example Code - HELLO2.C

int main()
{
  int i;
  for (i=0; i< 10; i++)
    printf("%d\n");
}

• Compile code to assembly file
  • Creates a .ASM file

CC HELLO2.C

• Assemble Code to object file
  • Creates a .O file

AS HELLO2.ASM

• Link Code with C library to .COM executable file

LN HELLO2.O C.LIB

ALGOL-M Compiler

• Fizzbuzz example

BEGIN

INTEGER FUNCTION DIVBY(N, D);
INTEGER N;
INTEGER D;
BEGIN
  DIVBY := 1 - (N - D * (N / D));
END;

INTEGER I;
FOR I := 1 STEP 1 UNTIL 100 DO
BEGIN
  IF DIVBY(I, 15) = 1 THEN
    WRITE("FizzBuzz")
  ELSE IF DIVBY(I, 5) = 1 THEN
    WRITE("Buzz")
  ELSE IF DIVBY(I, 3) = 1 THEN
    WRITE("Fizz")
  ELSE
    WRITE(I);
END;

END

• To run compiler:

algolm fizzbuzz

• Result is:

ALGOL-M COMPILER VERS 1.1
   0 ERROR(S) DETECTED

• To run ALGOL interpreter

runalg fizzbuzz

• Result is

ALGOL-M INTERPRETER-VERS 1.0


     1
     2
Fizz
     4
Buzz
Fizz
     7
     8

Microsoft BASIC Notes

• SAVE "MYPROG.BAS"
• LOAD "MYPROG.BAS"
• SYSTEM -- Return to CP/M
• NAME "OLDFILE.BAS" AS "NEWFILE.BAS"
• NEW - Delete program
• OUT 132,1 -- Output to I/O port 132
• PRINT MEM - Free memory (6809 Extended BASIC)

Notes

• Z80 Protocol Decoder
• Z80 = mc-2g-1024 - Best build
• Z80 Assembly Language books - archive.org

NASCOM BASIC

• OUT ADDR,DATA
• INP(128) - Reads I/O address 128 (0x80)

6502 CPU

Ohio Scientific SuperBoard II - My first commercial personal computer

SuperBoard II

• Manufacturer: Ohio Scientific
  • Model 600 Rev B Board Manual
• Model: Superboard II ( Model 600 )
• Available: 1978
• Price: US $279 assembled
• CPU: 6502
• RAM: 4K static RAM, 8K max
• CEGMON - Monitor in 4K of EPROM
• Display: composite video, 30 X 30 text
• Built-in keyboard
• Single board design
  • I eventually got a RAM expansion card with Floppy Disk Controller
• Ports: composite video, cassette
• Storage: cassette
• Microsoft BASIC
• 2K Monitor ROM (CEGMON)
• Compkit 101 - British clone of the SuperBoard II

Superboard II Documents

• Dave's OSI Repository - Lots of scanned documents up there - large file sizes
• Compukit UK101 Docs on Sourceforge]
  • CEGMON Users Guide
  • Sample Programs and Tapes
• CEGMON – a blast from the past
• Code for the 6502 microprocessor, mostly for the Replica 1 computer
• Nice page on the C1P/Superboard II
• 6502 Instruction Set

Keyboard Layout

CC65 - C Compiler for the 6502 and OSI C1P

• Ohio Scientific-specific information for cc65
• cl65 Users Guide
• CC65 - C Compiler for the 6502
• CC65 Wiki

SuperBoard II Emulator

• OSI Challenger 1P (8Kb) with Debugger - JAVA web based emulator
• OSI Challenger 1P (32Kb) with Disk Support - JAVA web based emulator
• pill_6502: 8-bit 6502 CPU and 6850 ACIA emulation on the STM32 blue pill to run Microsoft BASIC from 1977

BASIC Programs

10 I=1
20 PRINT "HELLO DAVEY"
30 I=I+1
40 IF I < 5 GOTO 20

SuperBoard II/ Retro-Tech Refresh

I was looking around for a way to recreate my OSI Superboard and found Grant Searle's design.

• EP2C5-DB - Our creation of a daughtercard which implements Grant Searle's Multi-Computer
• Grant Searle's CompuKit UK101
  • Based on Cyclone II EP2C5 Mini Dev Board
  • Someone built one of the CompuKit clones as a CPM box
• Compukit 101 video
• Ohio Scientific publications
• Enhanced 6502 BASIC
  • Experience porting Enhanced Basic to a 6502 Computer
    • "EhBASIC is about 11 KB"
• 6502.org - the place for retro 6502 projects
• System68
• L-Star: Software-Defined 6502 Computer - Uses a Propeller chip
• Pick-and-mix to create your own custom computer on a low-cost FPGA board
• Daryl's Computer Page
  • Daryl has designed multiple single board computers
• 6502 Assembly Language books - archive.org
• Micro 6502 Journal

6809 CPU

Our Build

• Our FPGA Builds
• BASIC is a port of Microsoft Extended BASIC for the 6809-based Radio Shack Color Computer

Neal Crook's 6809 Multiple OS Build

Neal Crook started from Grant Searle's Multicomp and fixed a number of issues with the VHDL code.

• Neal Crook's 6809 Wiki of Multicomp FPGA builds - very helpful
• Neal Crook's Multicomp GitHub (with docs)
• Neal did work on the 6809 core that Grant Searle was using
  • Changed reset to active-low, consistently asynchronous
  • Changed clock to rising-edge
  • Clocked the processor on the input (50MHz) clock rather than a divided clock
    • Used the HOLD input to control the clock rate.
  • Added MMU to control extended RAM
• Neal did some Video Display Unit (VDU) Modifications
• Neal's Memory Mapper
• Neal got SDHC working - the original was SD only

Programming

• CamelForth

SD Card

• SD Card image multicomp09_sd.zip - Program SD card using Balena Etcher
  • SD Card Image
• Using the SD Card

Other Docs

• Starting FORTH - First book of learning FORTH
• FUZIX
• Flex User's Guide
• Upload ROMs without rebuilding
• 6809 Emulation Page
• N8VEM 6809 Board
• asm6809 - Assembler

68000 CPU

Various 68000 builds

TG68_AMR Design

TG68 AMR Build

• Features
  • 68000 Core
  • SDRAM support
  • VGA Framebuffer
    • Pixel dithering maps 24-bit video to six bits
    • Various resolutions
    • Stored in SDRAM
  • PS/2 Keyboard and Mouse support
  • SD Card support
• Runs on RETRO-EP4CE15 basecard
  • VGA connector
    • 6 bit video (2:2:2)
  • PS/2 connector
  • FTDI USB to serial converter
    • Genuine FT230XS FTDI USC to Serial chip
    • USB B
    • Tx/Rx LEDs
  • SD or SDHC Card
    • Can do micro SDHC card using SD card adapter

• FPGA cards are
  • QMTECH EP4CE15 FPGA Card
  • QMTECH EP4CE55 FPGA Card
  • QMTECH 5CEFA2F23 FPGA Card
  • QMTECH EP4CE15 Standalone Board

TG68_AMR Links

• AMR's TG68 Experiments - Original design
• My GitHub page
• Hackaday page

TS2 design with Multicomp parts

• 68000 CPU in VHDL running on FPGA card
  • Running on RETRO-EP4CE15 card
  • Runs TS2BUG monitor or TUTOR from ROM
  • Built-on Video Display Unit (VDU)
    • Color attributes
    • XGA 80x25 ANSI character display
    • Extended (256) character set
  • PS/2 keyboard
  • 32KB SRAM
  • 16KB ROM
  • Loads/run Tiny Basic
    • Type LOAD on VDU port
    • Copy/paste S1/S9 records from TBI68K.HEX into ACIA port
    • JUMP 0900 to run

TS2 Links

• Jeff Tranter's build (BLOG) - TS2 build
  • Test Programs
  • Monitor code
• Educational Computer Board (MEX68KECB)
  • Motorola MC68000 Software
  • Motorola 680x0 Resources

68000 Software

• Tiny68K
  • t68kbug Debugger
  • Linux toolchain for the MC68000 CPU - gcc (Linux - uClinux/MC68000)
• Building uClinux for a 68000 Target
  • uClinux Sourceforge
  • 68000 booting uClinux 2.4.x (with 4Gb sdhc card) - YouTube video
  • Minimal hardware requirement for uClinux
• Installing binutils and GCC as cross-compiler for the Motorolla 68000
• EmuTOS - Free operating system for Atari computers, and more
• The LLVM Compiler Infrastructure - 68K backend
  • LLVM Project
  • Getting Started with LLVM

Other People's 68000 Builds

• comp.sys.m68k Frequently Asked Questions (FAQ) (1996)
• MiniMig TC64
• Hackaday 68000 pages
• 68000 brought to life!
• Kiwi - a 68k Homebrew Computer

RISC V CPU

• RISC-V Core
• biRISC-V - 32-bit dual issue RISC-V CPU

BASIC

• BASIC Programming Resources and Chipmunk Basic Archive
• Tiny BASIC
• Itty Bitty Computers & TinyBasic
• TINY BASIC User Manual

DEC (Digital Equipment Corp) Computers

• Computer Simulation and History (simh)
  • Introduction to SimH -- basic usage - YouTube - Stephen's Machine Room
• Herb's DEC items

PDP-4

• PDP-4 on FPGA
• PDP-4/X System Reference Manual

PDP-8

• My PDP-8 Hardware GitHub repository
• History of the PDP-8
• Highgate's PDP-8 Page

Build of Tom Almy's PDP-8 FPGA (Working 2021-May)

My build is based on Tom Almy's book The PDP-8 Class Project: Resoling An Old Machine.

• PDP-8 FPGA - Hackaday page with progress logs
• Hardware used
  • RETRO-EP4CE15 - FPGA Hardware used
    • QMTECH EP4CE15 FPGA Card
  • PDP-8 Front Panel
• FPGA Code
  • PDP-8 Almy book on GitHub
• My PDP-8 Software GitHub repository

OpenCores PDP-8 Build

• opencores PDP-8 Processor Core and System Overview
  • Quickstart page
• My GitHub repository
• Hardware used
  • RETRO-EP4CE15 - FPGA Hardware used
    • QMTECH EP4CE15 FPGA Card
  • PDP-8 Front Panel
• FPGA Code
  • FPGA files

Others PDP-8 FPGA

• Another Almy based design - In Verilog
• Yet another Almy based design
• PDP-8 in VHDL
• A FGPA Implementation of the PDP-8
• PDP-8/I on an FPGA
• PDP-8/i cpu with an RF08 disk emulator Uses a IDE disk as a backing store. It boots TSS/8.
• PDP-8 Instruction verification - In System Verilog?
• PDP8 in a Cypress PSoC5
• Scott Baker's PDP8-SOC - Clean VHDL Design

PDP-8 Documents and Programming

• Maintenance Manual - excellent document (pdf)
• PDP-8 - A Programmer's Reference Manual
  • The Digital Equipment Corporation PDP-8 - Memory Reference Instructions
• PiPDP-8 Front Panel
• PDP-8/X System Reference Manual (pdf)
• Front Panel software
• pdp8online.com
• PDP-8 Assembly Language Studio
  • Conway’s Life Implemented in PDP-8 Assembly Language

PiDP-8

• PiDP-8/I: RECREATING THE PDP-8/I - Obsolescence Guaranteed
• PiDP-8/I software development nexus

PDP-10

• PDP-10 on FPGA
  • Archived on retrobrew site

PDP-11

My PDP-11 (pdp2011) FPGA builds

• PDP-11 ON RETRO-EP4CE15 - Works
• Based on Sytse van Slooten's original design pdp2011

Other PDP-11 FPGA builds

• Dave Richards pdp2011
• PDP-11 in VHDL - W11 build

PDP-11 Software

• System Disk Images
• Disk Images
• PDP-11 Processor Handbook 1981 - on BitSavers
• PDP-11 on BitSavers
• PiDP-11: Replica of the 1970s PDP-11/70 emulated on Raspberry Pi
• PDP11 Assembler

Terminal

Grant Searle Terminal Design

• Uses two Arduino'ish processors to implement an entire terminal
  • NTSC output
  • PS/2 Keyboard input
• Grant Searle's Monitor Keyboard Design

• Older AtMEGA32 version of Monitor Keyboard Design

• My implementation of Grant's small serial terminal design

External Sites

PiGFX

• PiGFX Raspberry Pi graphics card / ANSI terminal emulator

• PiGFX is a bare metal kernel for the Raspberry Pi that implements a basic ANSI terminal emulator with the additional support of some primitive graphics functions.
• It can be driven by pushing characters to the raspi UART.

https://raw.githubusercontent.com/fbergama/pigfx/master/doc/scr1.jpg

RetroBrew Computers Site

• RetroBrew Computers Forum
• pagetable - Probably the best C64 technical data out there
  • Github for all things C64
• S-100 Bus FPGA Z80 SBC Board