RetroComputers

Our Retro-Computer Projects

MultiComp On EP2C5

• Land Boards EP2C5-DB FPGA Retro-Computer card
  • Attaches to Cyclone_II_EP2C5_Mini_Dev_Board
  • Duplicates Grant's design down to the same pin maps

MultiComp On RETRO-EP4

• Land Boards RETRO-EP4 design
  • Attaches to Cyclone II EP2C5 Mini Dev Board
  • 512K Fast SRAM
  • FTDI USB-to-Serial Interface with Hardware Handshake
  • 6-bit (3/3/3) VGA
  • PS/2 connector
  • 5V Power Module
  • Lot of I/O connections

MultiComp On RETRO-EP4CE15

• Land Boards RETRO-EP4CE15 design
  • Attaches to QM Tech Cyclone |V FPGA Board or
  • Attaches to QM Tech Cyclone V FPGA Board
  • 512K Fast SRAM
  • FTDI USB-to-Serial Interface with Hardware Handshake
  • 6-bit (3/3/3) VGA
  • PS/2 connector
  • 5V Power Module
  • Lot of I/O connections

[[File:P981-720px.jpg]

MultiComp On BASE-EP4CE6

• Land Boards BASE-EP4CE6 card is a breakout board
  • Attaches to Land Boards EP2C5-DB card
  • Adds extra logic and RAM resources beyond the EP2C5 FPGA
    • Can do up to 16K of Internal SRAM
  • Wiring is here

Purchased FPGA Cards

MultiComp On A4-CE6 Card

• Wiki page for Cyclone IV FPGA EP4CE6E22C8N Development Board

Features for MultiComp Use

• Enough Internal SRAM to make small (16KB) BASIC computers
• Includes VGA, PS/2 and CH340 USB-Serial converter
• A lot of I/O (26 pins) which can be easily accessed using EP4 FPGA BREAKOUT
• LCD Display connector with additional I/O

Limitations on MultiComp compatibility

• No native SD Card storage but could be built using EP4 FPGA BREAKOUT and SD CARD X49
• 1:1:1 video does not support 2:2:2 (bold characters under ANSI terminal)
• Serial Hardware handshake with a small rework to the card (2 wires)

Additional Features

• 8 Digit 7 Segment Display
• 8 position DIP switch
• 3 User pushbuttons, 1 DEV-OE pushbutton, 1 nCONFIG pushbutton
• 12 "Ring" LEDs - 2 removed and used for hardware handshake rework
• 24C04 I2C EEPROM

MultiComp On A4-CE10 Card

• Wiki page for Cyclone IV FPGA EP4CE10E22C8N Development Board

Features for MultiComp Use

• Enough Internal SRAM to make small (32KB) BASIC computers
• Includes 5:6:5 VGA, PS/2 and CH340 USB-Serial converter
• A lot of I/O (26 pins) which can be easily accessed using EP4 FPGA BREAKOUT
• LCD Display connector with additional I/O

Limitations on MultiComp compatibility

• No native SD Card storage but could be built using EP4 FPGA BREAKOUT and SD CARD X49
• 1:1:1 video does not support 2:2:2 (bold characters under ANSI terminal)
• Serial Hardware handshake with a small rework to the card (2 wires)

Additional Features

• 8 Digit 7 Segment Display
• 8 position DIP switch
• 3 User pushbuttons, 1 DEV-OE pushbutton, 1 nCONFIG pushbutton
• 12 "Ring" LEDs - 2 removed and used for hardware handshake rework
• 24C04 I2C EEPROM

MultiComp On A_ESTF_V2_EP4CE22 Card

• Wiki page for [1]

Features for MultiComp Use

• Includes VGA, PS/2 and USB-Serial converter
• A lot internal SRAM (up to 56KB)
• MicroSD card socket with card detect LED

Limitations on MultiComp compatibility

• No external SRAM but very large SDRAM
• A lot of I/O options
• Not widely available
• Has no USB-Serial Interface (has RS-232)

Additional Features

• A lot of I/O pins on the base board and on the FPGA board
• Eight 7 Segment Displays
• 3x3 matrix of pushbutton switches
• 3 user pushbutton switches on baseboard
• 3 user pushbutton switches on FPGA board
• Buzzer
• IR receiver
• Power switch
• 24C02 I2C EEPROM
• 8 position DIP Switch

MultiComp On ZrTech Cyclone IV FPGA Card

• Wiki page for Purchased EP4 FPGA card
• Marked as zrTech V2.00
• We did a YouTube video series on this card.

Features for MultiComp Use

• Includes VGA, PS/2 and USB-Serial converter
• Enough Internal SRAM to make small (16KB) BASIC computers

Limitations on MultiComp compatibility

• Very limited I/O
  • Most of the I/O pins are shared with the 16-bit Video
  • Would require removing R-packs to gain I/O
• Driver for USB-Serial doesn't work under Windows 10 (painful workaround)
• No SD Card storage
• No external SRAM but very large SDRAM (not supported yet in our builds)
• Would require a mod for serial hardware handshake (there's a pin or two free on the I/O which could at least do RTS)

Additional Features

• On/Off switch - nicer than plugging/unplugging DC power cable
• 4 pushbuttons
• Four digit 7 Segment Display
• IR LED
• Buzzer
• A/D with SMA connector

Additional FPGA Support Cards

These cards provide some of the missing functionality of the purchased FPGA card.

EP4 FPGA BREAKOUT

• Wiki page for EP4 FPGA BREAKOUT
• Daughtercard for
  • Cyclone IV FPGA EP4CE6E22C8N Development Board
  • Cyclone IV FPGA EP4CE10E22C8N Development Board

VGAX49

• VGAX49 Wiki page
• Digital VGA adapter
• 16-bit digital video
  • 5:6:5 (R:G:B) mapping (maximum)
  • 2:2:2 (R:G:B) mapping (option)

SD CARD X49

• SD CARD X49 Wiki page
• SD or SDHC card adapter
• 5V to 3.3V regulator
• 3.3V to 5V TXS0104E level shifter
• Activity LED

TinyPS2

• TinyPS2 Wiki page
• PS/2 keyboard or mouse to TTL Level Serial converter
• ATTiny85
• 115,200 baud
• 49x49mm ODAS form factor
• 4-40 mounting holes

FTDI-49MM

• FTDI-49MM Wiki page
• FTDI FT230X IC
• USB B connector (not micro or mini, but the beefy USB B connector)
• FTDI compatible pinout
• 3.3V or 5V selection jumper
• Header for 5V power distribution
• Rx and Tx LEDs

Multicomp

• Multicomp Github repo
• 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

Grant Searle's FPGA MultiComputer Project(s)

• MultiComp Wiki Page on GitHub

Our Retro-Computer Video Series

EP2 Video Series

Video Series

EP4 Video Series

Video Series

Z80 CPU

• Land Boards Z80 in 3 Chips
• Hackaday Z80 in 3 Chips

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
  • Two UART Serial interface
  • No Video Display
  • External RAM

Retrobrew Computer Builds of the Multicomp Project(s)

• MultiComputerZ80 build - Lots of extras
• 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
• Z80 BASIC on a Cyclone IV FPGA

CP/M Resources on the Net

• CP/M Operating System Manual
• Digital Research CP/M Site
• A Short History of CP/M
• BBC BASIC (Z80)
  • BBC BASIC (Z80) Manual
• 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

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 - copy command
• PIP NEWCOPY.EXT=COPYFROM.EXT - Copy from COPYFROM.EXT to NEWCOPY.EXT
• Drive references A:
  • Drives go from A-???
• LS is a better direction program

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

• 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.

• 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)

S120 Bus Computer

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 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

6502 Computer Projects

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

6800

• My first attempt to build a computer was around an MC6800 CPU so it has a soft spot in my heart

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

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

6809 CPU

Neal started from Grant Searle's work and fixed a number of issue with the VHDL code.

• Neal Crook's Wiki Page
• 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
• Neil Crook's 6809 Multicomp FPGA builds - very helpful
• Neil Crook's 6809 Wiki of Multicomp FPGA builds - very helpful
• Starting FORTH - First book of learning FORTH

68000 CPU

• 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

Other People's 68000 Builds

• Jeff Tranter's build (BLOG) - TS2 build
  • Test Programs
  • Monitor code
• Educational Computer Board (MEX68KECB)
  • Motorola MC68000 Software
  • Motorola 680x0 Resources
• comp.sys.m68k Frequently Asked Questions (FAQ) (1996)
• MiniMig TC64
• Hackaday 68000 pages
• FUZIX
• Tiny68K
  • t68kbug Debugger
• 68000 brought to life!
  • Linux toolchain for the MC68000 CPU - gcc (Linux - uClinux/MC68000)
  • 68000 booting uClinux 2.4.x (with 4Gb sdhc card) - YouTube video
  • Minimal hardware requirement for uClinux
• Building uClinux for a 68000 Target
• uClinux Sourceforge
• Installing binutils and GCC as cross-compiler for the Motorolla 68000

BASIC

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

DEC (Digital Equipment Corp) Computers

• PDP-11 on A-ESTF FPGA
• PDP-8 in VHDL
• A FGPA Implementation of the PDP-8
• PDP-8 Processor Core and System :: Overview
• The Digital Equipment Corporation PDP-8 - Memory Reference Instructions
• PDP-11 in VHDL
• Computer Simulation and History
• Herb's DEC items

External Sites

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

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