Table of Contents
I worked with 68K processors during the early phase of my professional career for embedded applications, but I am unfamiliar with how 68K were used in desktop applications. I like to explore the various uses of 68K in the general desktop usage which means interface with disk, keyboard, ethernet, USB, video and operating systems.
During the recession of 2007/2008 I had many opportunities to collect 68K components, memories, and peripherals at bargain basement prices mostly on eBay and some on local electronic auctions. I purchased them as memorabilia and to tinkering with during my retirement. I'm retired now and this is a record of my tinkering. Here is an important set of tools for tinkering.
As my exploration evolved, I also became interested in Z80 and Z280, especially Z280 which is an obscure but surprisingly modern CPU.
Tiny030 is described at end of the page. It will be moved to here later on.
CB030 is follow-on to Tiny030; it'll have more memory, compact flash mass storage, and I/O expansion.
MB020 is a 4“x4” 68020-based motherboard with 3 RC2014 expansion slots. It allows RC2014 users to reuse their existing hardware to explore the 68020 processor.
Tiny020 is described near the end of this page. It will be moved here later.
MB012 is a 4“x4” 68012-based mother board with 2 I/O expansion slots.
P90CE201 is derived from 68000 but with integrated I/O that includes two I2C buses. It is not well known and I heard about it from a Facebook posting and bought a few parts from eBay. I plan to design a motherboard with it and one for Arduino Mega enclosure. First thing is a quick prototype to check out its capabilities.
X688 is quick prototype board to check out the P90CE201 I purchased from eBay.
P90MB is a motherboard based on P90CE201 with 3 RC2014-like expansion slots.
68Kuno (Kuno) is P90CE201 SBC designed for Arduino Mega enclosure
Z80ALL is a Z80-based CP/M ready standalone computer with monochrome VGA interface
GRC stands for “Generic Retro Computer”. It is a new modular computer ecosystem for 8-bit processors of 1970 and 1980.
SBC for RC2014
I stumbled across the RC2014 community in early 2018. I like the simple backplane and large collection of I/O modules. The single inline connector can also plug into a solderless breadboard for prototyping experiments.
Prototype Z1RCC based on modified RIZ180 pc board. A RC2014-compatible, RomWBW-capable, Z180 SBC
ZZRCC is a single-board computer in RC2014 format (50mm X 100mm) based on Z280 processor.
RIZ180 is a simple Z180-based SBC with RC2014 expansion slots
ZRC is another simple CP/M-ready Z80 SBC capable of running ROMWBW
ZoRC, exploratory is an even simpler implementation of CP/M-ready Z80 SBC.
ZRCC, Z80+RAM+CPLD+CF disk
ZRCC, rev1 is designed as an inexpensive RC2014-compatible, CP/M-ready kit.
Z280RC is a CP/M-ready SBC Z280 designed to plug into the RC2014 and interface to its many I/O modules.
ZZ80RC is a CP/M2.2-ready SBC based on Z280 processor configured to operate in the Z80-bus compatible mode. It is designed to plug into the RC2014 bus.
ZZ80RC-CF is an enhanced version of ZZ80RC with a CF flash interface. Like ZZ80RC, it is in all through-hole technology in standard RC2014 format of 100mm x 50mm.
A Z280-based motherboard with expansion slots. The basic design is based on ZZ80RC-CF
Z80LCD is a dedicated Z80 SBC to control a 320×240 LCD display panel, UG32F01
Z80 single board computer for RC2014 is in the standard RC2014 format of 100mm x 50mm. It is a ROM-less implementation that operates at 20MHz. It also has a compact flash interface.
Z80SBC64 is a hobbyist friendly version of Z80SBCRC. All components are in through-hole technology and remain in the standard 100mm x 50mm board size.
A mother board based on Z80SBC64 with 3 RC2014 expansion connectors.
Generic 8-bit processors prototype board is a hybrid board with printed wirings and prototype area to accommodate different 8-bit, 5V processors of 1970's and 1980's. G8PP in baseline configuration serves the function of clock, paged memory, compact flash, and serial port for RC2014, resulting in a CP/M capable RC2014 system with the addition of the Z80 CPU board.
G8PP Base (need better name) is a G8PP in baseline configuration plus a processor board on a RC2014 backplane. The control signals of RC2014 (nM1, nMREQ, nRD, nWR, nIORQ) as well as the 4 spare signals are reassigned depending on the targeted processor. No hardware changes are required when change to a different processor board, but the CPLD must be reconfigured and new processor software loaded.
- G8PP + 1802
- G8PP + 32008
T68KRC, rev0.1 is Tiny68K that plugs into the RC2014 backplane and interface to its many I/O modules.
T68MB is T68KRC with 3 RC2014 expansion bus added. It also has a dedicated I2C connector for 128×64 OLED display.
A simple traditional SBC design with 3 RC2014 expansion connectors but without glue logic.
Simple80 Rev 1. The compact flash interface is on board. It is software compatible with original Simple80
A glue-less Z80 SBC similar to Simple80 but uses KIO (Z84C90) instead of SIO
EaZy80 Rev0. Requires significant engineering changes
A traditional SBC design using a KIO (Z84C9012) and over-clocked to 22MHz. It also has 2 RC2014 expansion connectors.
A traditional Z80 SBC design using Z84C15. It also has 3 RC2014 expansion connectors
These are modules designed for the classical RC2014 backplane
AllCF is a compact flash or disk-on-module interface for RC2014
Diagnostic Module for RC2014. A low cost programmable multi-function logic analyzer and diagnostic aids for bringing up a RC2014 system.
Four serial ports (using 80-pin TQFP OX16C954) with 128-byte deep FIFO each for RC2014
Hobbyist-friendly quad serial board with all through-hole components
A text-based VGA display based on dual port RAM
KIORC is a module for RC2014 based on KIO, Z84C90
A module for RC2014 with 6 hex displays made of individual LED
Frugal RAM/ROM 512K
A very low cost RAM/ROM 512K with CF interface and I2C interface
Improved 512K RAM/ROM
A module for RC2014 with improved 512K RAM, 512K flash, and CPLD
Rev1 of Improved 512K RAM/ROM. This version is a simplified design features all through-hole components for ease of assembly.
ProtoRC is a 100mm x 100mm prototype board. It centered around an Altera EPM7128 CPLD which interface RC2014 signals on one side and 0.1“ grid array experiment area on the other side.
- ProtoLCD is prototype of 4-line LCD display on a ProtoRC board.
- ProtoSIO2 is prototype of Zilog SIO/2 serial device on a ProtoRC board
- ProtoSound is prototype of AY2149F on a ProtoRC board.
ProtoRC1 is a 100mm x 75mm prototype board. It centered around an Altera EPM7128S CPLD. There are more dedicated 7-segment displays and compact flash interface. The prototype area is limited to one row of 300-mil or 600-mil DIPs.
- ProtoCF is a 8-bit compact flash interface on ProtoRC1 board
- ProtoSD is a SD card interface on ProtoRC1 board
- FrontPanel enters data into Z80 via PS2 keyboard, run/single-step Z80, and display address/data on 7-segment display
ProtoRC2 is very similar to ProtoRC1 with the addition of a connector for 4×20 LCD character display.
ProtoRC3 uses through-hole components only. The CPLD is Altera EPM7064S in 44-pin PLCC package socketed in a through-hole PLCC socket.
ProtoRC4 uses EPM7064STC100 that was recovered from recycled pc board
ProtoR5 uses EPM7192SQC160.
- Proto65 is a 6502 SBC based on ProtoR5
DPRAM is a prototype board based on IDT7134 dual port RAM to explore multiprocessor system. This version has a Z80 running as a slave processor and a EPM7064S CPLD as glue logic.
SBC for Arduino Mega Enclosure with RC2014-Compatible Expansion Bus
ZRuno is ZRCC for Arduino Mega enclosure
Kuno is P90CE201 designed for Arduino Mega enclosure
MicroZ is the Micro80 above but designed for the acrylic Arduino Mega enclosure
Zuno is Z80SBC64 designed for the acrylic Arduino Mega enclosure
Shields for Zuno
Shield for RGB Panel
Shield for RGB Panel is a 2”x4“ thin pc board with connectors that plugs into the I2C connector of Zuno. It hosts a 5×10 array of RGB LEDs
RC2014 Modifications and Upgrades
RC2014 Mini Upgrade to CP/M
Step-by-step instruction to upgrade RC2014 Mini to run CP/M2.2
The goal is a modular stand-alone 6502 system with RC2014 backplane and repurposed RC2014 boards
CRC65 stands for CPLD+RAM+CF+6502. It is an inexpensive, yet high performance 65C02 single board computer
CRC816 is CRC65 modified to accommodate W65C816 CPU.
VGA6448 for CRC65 is a monochrome, 64 column X 48 lines text-based VGA video board for CRC65.
OC65 usesCRC65 design concept but overclocked to 36MHz and beyond!
OVRCLK65 is overclock experiment prototype for 6502 and 65816
QuadSer is four high-speed serial ports reconfigured for 6502,
CPLDTIL is 6-digit discrete LED display reconfigured for 6502,
ProtoRC is a family of RC2014 prototype boards that can be reused for 6502.
Other 6502 projects
VGA65 is CRC65 modified as a VGA video board.
Proto65 is an evolving project for building a standalone 6502 computer.
Prog65 is a ROM-less 6502-based EPROM programmer that also serves as a simple 6502 single board computer.
ZG6502 is a zero-glue-logic 6502 single board computer consists of RAM, EPROM, 6502 and 6551.
- Prog65ZG is prototype version of ZG65.
CPLD6502 Trainer is a CPLD educational board with 6502 as the processor.
Apple IIe Projects
I purchased two Apple IIe in 2021. These are projects for Apple IIe
I was shocked to find out how cheaply pc boards can be fabricated, especially in the 100mm x 100mm format. This capability encourages modular construction in the size of 100mm x 100mm format and the 80-20 prototyping approach of 80% pc board and 20% hand wiring. Unfortunately, most of the board shops are in China, so there are greater cost in shipping and turn-around time. I can amortize the cost and better use the waiting time by working on multiple projects at the same time. The “Tinyxxx” naming convention denotes the 100mm x 100mm format (Tiny) followed by the name of processors, e.g. Tiny030 is the MC68030 pathfinder in 100mm x 100mm format. For ease of construction, I prefer through-hole components over surface-mount components and I'll stay with the 5V components for now.
The 68302 is one of the early 68000-based MPU of the 683xx family. The availability of System Integration Module and abundance of I/O devices make it easy to interface thus it is the first path finder project.
Tiny302 construction log
MC68020 is arguably the most perfectly crafted 32-bit CPU. The dynamic bus sizing makes it easy to interface with 8-bit wide memories and peripheral; low power consumption means external heat sink is not necessary; abundance of registers and orthogonal instruction set make writing assembly level language easy; vector base register allows relocation of the exception tables; coprocessor architecture for expanded features notably the floating point and memory management; and it is widely used so parts & tools are readily (cheaply) available. I want to build Tiny020 in the “retro” style which means using through-hole TTL glue logics.
Tiny020 pc board
Tiny020 construction log
MC68030 is a mc68020 with integrated memory management unit plus data cache. I want to do Tiny030 for 3 reasons: I stumbled across a box of new, never opened, wrongly-labelled 68030 tucked away in the garage. I believe it was a part of large crate I successfully bidded on in a local auction and it may well be the most valuable item in that lot sitting there unopened for 10 years! I also want to use the large pile of 4/8/16 megabyte SIMM72 memory modules, and I want to check out Altera's tools by using the EPM7128 CPLD as the glue logic. Since I'm already successful with Tiny020, I'll use the 80-20 pcb-handwiring approach.
Tiny030 pc board
Tiny030 monitor debugger
MC68040 is effectively the end of line for the 68K family. There is 68060, but it was not widely used and part is hard-to-find and expensive. I may work on a 68060 later, but not as a path finder project. The first concern with 68040 is power management. It is a power hog and heat sink design is essential–not ideal in the prototype development environment. 68040 does not have dynamic bus sizing, so all executable memory MUST be 32-bit wide. An external dynamic bus sizer can be used, but there is no space for it in the Tiny format. I'm better off using 4x 8-bit flash for boot ROM and SIMM72 for RAM.
Explore the concept of $10 68K initially proposed here: https://www.retrobrewcomputers.org/forum/index.php?t=msg&th=152&goto=2253&#msg_2253
Tiny68K pc board
Tiny68K construction log
Prototype Z280 board in 100mm X 100mm format
Overclock SC114 and other modifications
VGA piggybacked on RAM, a VGA prototype glued on top of a 128KB RAM and displays content of RAM as 64-column by 48-line VGA display
K. Orton's ZX79, a minimalistic Z80 computer
PLCC32 to DIP32 adapter
Soldering SMT components
Repurpose the ADC SPX-MPU board–MC68302 single board computer
CP/M 68K on the MPU302, a repurposed ADC SPX-MPU board