65816 Computers

August 31, 2022

There’s a corner of vintage/retro computers universe that doesn’t receive much attention and thats the suped 6502 machines based on the 65816 micoprocessor. The 65816 can be described as a 65C02 on steroids.

The 65816 was a 16-bit implementation of the classic 6502 microprocessor. Designed by 6502 veteran designer Bill Mensch and made by Western Design Center, Inc. (WDC) which Mensch founded in 1978 they would find fame in the Acorn Communicator (1985), the Apple //gs (1986), Super Nintendo (1990) and various Commodore 64 accelerator cartridges.

Here’s a list of some recent 65816 computer builds:

C64 SuperCPU
https://www.c64-wiki.com/wiki/SuperCPU

Flash 8 – C64 accelerator cartridge
https://www.c64-wiki.com/wiki/Flash_8

WDC SBC
https://wdc65xx.com/Single-Board-Computers/w65c816sxb/

The Mensch Computer
https://www.westerndesigncenter.com/wdc/Mensch_Computer.php

WE816
https://github.com/danwerner21/we816

PC-65816
https://www.rehsdonline.com/blog/categories/65816-1
https://github.com/rehsd/PC-65816

65816 computer
https://mike42.me/blog/2022-01-a-first-look-at-the-65c816-processor
https://github.com/mike42/65816-computer

Ruby ‘816
https://projects.drogon.net/65816-ruby/

JRC-1
https://www.area73.us/jrc-1/
https://hackaday.io/project/185467-jrc-1
https://github.com/jmthompson/jrc-1

Adria – A 65C816 based computer
https://hackaday.io/project/177856-adria-a-65c816-based-computer
https://github.com/Zchander/adria

BCS TECHNOLOGY
http://sbc.bcstechnology.net/

65C816
https://github.com/adrienkohlbecker/65C816

CS/A 65816 CPU
http://www.6502.org/users/andre/csa/cpu816/index.html

CS/A 65816 V2 CPU
http://www.6502.org/users/andre/csa/cpu816v2/index.html


Dragon 32 at 40, Repairs and Mods

July 31, 2022

The Dragon 32 is a much underrated 1980’s home computer. This Welsh wizard was released in August 1982, so it is now 40-years old and deserves some recognition.

Tony Smith wrote a great piece on its history back in 2012

So if you’ve got a Dragon and are looking for some help in keeping it breathing then here’s a few links:

Dragon 32 Garbage to Gold (Will it fly again?)
https://www.youtube.com/watch?v=PXZfqn2rnIc

Dragon32 Trash to Treasure | When Wales made a Micro Computer (pt1)
https://www.youtube.com/watch?v=1mgeeG_1qIs

Dragon32 Trash to Treasure | Repairing the Dragon (pt2)
https://www.youtube.com/watch?v=7NUhKTe12v0

Dragon32 Trash to Treasure | Rise of the Dragon32 (pt3)
https://www.youtube.com/watch?v=i5Y4Cf1o8yI


Tynemouth Software blog returns

June 30, 2022

I’m not sure how I missed this blog post but Dave Curran’s Tynemouth Software blog is back. I was sad to see the blog go offline in 2020 during the recent pandemic. But its great to see him back now.

If you don’t know Dave’s work he’s the creator of many great retro computer projects:

  • Mini PET 40/80 – A Commodore PET stand alone computer kit
  • Minstrel 2 – A ZX80 compatible computer kit
  • Minstrel 3 – A ZX81 compatible computer kit

to share just a few.

And he authors many great blog posts on repairing old computers and also posts detailed explanations of their workings.

Our paths have crossed on a few occasions, mainly at the much missed Maker Faire UK when it was held at the Newcastle Centre for Life.


C64 PLA Replacement

May 31, 2022

Whilst some 1980’s computer manufacturers, notably Sinclair and Acorn, would used Uncommitted Logic Arrays (ULA) to reduce IC component counts to reduce cost, Commodore would take a different path and would use Program Logic Array IC’s (PLA) in many of their computers, starting with the Commodore 64 (C64).

ULA’s are given their final logic configuration while still in their final stages of semiconductor manufacture and means it can take many weeks or even months for them to ready for use. This makes for a very cheap chip but any mistakes in the logic design would mean you had to scrap the ones you’ve just made and start again, adding cost and delay to your project. They lacked the flexibility of being programmable at point of printed circuit board assembly. But not so with Program Logic Array IC’s (PLA). PLA’s would be “blank” until they were needed and could be used on many different products. The PLA is an early example of field programmable chips.

The Signetics 82S100 PLA chips used in early Commodores and would be later replaced by their own design MOS 906114-01.

The success of Commodore was in part due to their business structure. They we very much a vertically integrated business which means they designed and made almost everything in their own factories. Making their own semiconductors by buying MOS Technology in 1976 was vitally important to that success. But not everything would be perfect with this setup.

Unfortunately as documented else where online, the semiconductor process used for MOS’s versions of PLA’s would eventually cause these chips to fail. The C64 PLA’s were reportedly contaminated with boron whilst being made at MOS’s semiconductor fabrication site.

Now fast forwarding to the present, finding direct replacements for this PLA is almost impossible but today there are many alternative and replacement C64 PLA out there. Here’s some I know of: PLA20V8, SuperPLA, RealPLA, PLAnkton, ezPLA, PLAdvanced, Ultimate PLA. If you know of any more drop me a line and I’ll add them to this list.

We’ll start with Marek over at his ezContents blog with has several good write ups on the C64 PLA and check out his Altera EMP7032 CPLD solution:

Troubleshooting C64 PLA chip replacement
https://ezcontents.org/troubleshooting-c64-pla-chip-replacement

Recreate C64 PLA chip in VHDL
https://ezcontents.org/recreate-c64-pla-chip-vhdl

ezPLA – C64 PLA replacement PCB
https://ezcontents.org/ezpla-c64-pla-replacement-pcb

ezPLA
https://github.com/marekl123/ezPLA-PCB

ezPLA-VHDL
https://github.com/marekl123/ezPLA-VHDL

Commodore 64 custom PLA chip test
https://ezcontents.org/commodore-64-custom-pla-chip-test

Commodore 64 PLA chip replacement
https://ezcontents.org/commodore-64-pla-chip-replacement

And heres the others:

Adrian’s Digital Basement has a video good video on the subject.
Can you replace your C64 PLA for under $3?
https://www.youtube.com/watch?v=GKyoh_gGTYM

Thomas Giesel’s excellent “The C64 PLA dissected” document from 2012
https://skoe.de/docs/c64-dissected/pla/c64_pla_dissected_a4ds.pdf
ftp://ftp.zimmers.net/pub/cbm/c64/firmware/C64_PLA_Dissected.pdf

Daniël Mantione captured his PLA20V8 replacment on his blog:
https://www.freepascal.org/~daniel/c64pla/

Doktor64
Doc64 #26 | Commodore C64 | What’s the PLA for and how does it work?
https://www.youtube.com/watch?v=BABOyg6j78w

PLAnkton a M27C512-90B6 EPROM based PLA
https://www.polyplay.xyz/PLAnkton-PLA-Replacement
https://www.melon64.com/forum/viewtopic.php?t=11696

Another interesting video is a talk by PLAnkton creator Francois Leveille

10 ‘The PLAin Truth About the Commodore 64 PLA’ at World of Commodore 2017

realPLA (by Thomas Giesela aka skoe)
https://www.c64-wiki.de/wiki/realPLA

SuperPLA V4 (by Jens Schönfeld from INDIVIDUAL Computers)
https://icomp.de/shop-icomp/en/produkt-details/product/superpla-v4.html
http://wiki.icomp.de/wiki/SuperPLA_V4

PLA20V8 consists of two GAL20V8B
https://www.freepascal.org/~daniel/c64pla/

FrankBuss/c64pla: C64 PLA implementation in VHDL
https://frank-buss.de/c64/pla/index.html
https://github.com/FrankBuss/c64pla

Bo Zimmerman and his web page
http://www.zimmers.net/anonftp/pub/cbm/documents/projects/memory/c64/


Apple II computer repair resources

April 30, 2022

I acquired a pair of Apple IIe’s some time ago which could need some retro TLC. Looking at them brought back some nice memories, the Apple II was the first computer I learnt to repair way back in the early 1980’s.

So before I jump in, I thought I would check out what repair documents are on the web and brush up my knowledge. So here’s a quick list of what I found.

A truly excellent collection of Apple II hardware documents:
https://downloads.reactivemicro.com/Apple%20II%20Items/Hardware/IIe/Schematic/

Always a great site to find old manuals and books. Just type in your search parameters:
https://www.archive.com

Apple II documentation project. Lots of great material:
https://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Computers/Apple%20II/

The Apple II peripheral port:
https://osites.tripod.com/peripheral.html

Apple2info
https://web.archive.org/web/20090515010203/http://apple2info.net/hardware.htm

Apple2History
https://www.apple2history.org/history/ah12/

Vintage Apple
https://vintageapple.org/

AppleLogic
http://www.applelogic.org/

Bitsavers project
http://www.bitsavers.org/

Here’s a few more pics:


More ZX Spectrum repair videos

March 31, 2022

Following up from my previous post for Sinclair ZX Spectrum repair videos, here’s a few more:

ZX Spectrum 48k Issue 2 Repair and Restore
https://www.youtube.com/watch?v=R9_HR3HcmUc

ZX Spectrum repair, restore and upgrade. Part 1
https://www.youtube.com/watch?v=D_tHUv5Xn-E

ZX Spectrum Part 2: Troubleshooting and fixing the ZX Spectrum
https://www.youtube.com/watch?v=wGcFcfxngdg

Sinclair ZX Spectrum 48k | Charity Repair and Refurb
https://www.youtube.com/watch?v=pNaArCoXWfQ

S-Video modification for ZX Spectrum 16k / 48k / 48K+
https://www.youtube.com/watch?v=-LAws3_BfLY

Removing Components from a Double-Sided Through-Hole Plated (ZX Spectrum) Circuit Board
https://www.youtube.com/watch?v=u_NnU48bmv4

ZX Spectrum (48K & 16K) Initial Tests
https://www.youtube.com/watch?v=IzgCmldm2H4

Replacing Electrolytic Capacitors in a ZX Spectrum
https://www.youtube.com/watch?v=TeCVt2T-YSo

ZX Spectrum Lower RAM Replacement Module
http://zx.zigg.net/LRR/

ZX Spectrum 48K – How to replace the ROM with an EPROM
https://www.youtube.com/watch?v=rJmJBWWoRpE

ZX Spectrum A TZXDuino inside a Cassette Tape?
https://www.youtube.com/watch?v=dMpGGf-YUzU


Awesome Computer History

February 28, 2022

I find it quite amazing that computers which are still a relatively new technology now need to have their history told and recorded, so their early discoveries and examples are available for future generations to admire. I found these interesting reads

https://github.com/watson/awesome-computer-history
https://github.com/cbmeeks/awesome-computer-history
has not been update for a few years but has many great links.

If you’re interested in interviews on retro computing, theregister.com is also a great resource for finding many more.


Commodore C64 replacement PSU options

January 31, 2022

I’ve got a Commodore C4 in my collection that doesn’t have an original power supply (PSU) so whilst I could just use a C64 from one of my other machines I thought I would investigate what DIY replacements are out there. So below is a short list of C64 PSU’s DIY builds I’ve found so far:

C64-replacement-PSU-230VAC
https://github.com/svenpetersen1965/C64-replacement-PSU-230VAC-

C64-PSU-Global
https://github.com/svenpetersen1965/C64-PSU-Global

Bwack’s C64 saver designs.
https://github.com/bwack/C64-Saver-bwack

Building a new C64 Power Supply
https://janbeta.net/c64-power-supply/
https://www.youtube.com/watch?v=IpuKz0TTB2I

Building a DIY C64 Power Supply (The Lazy Way)
https://www.youtube.com/watch?v=wWOU2sZv_ng

GWB#1 – Commodore 64 / 1541-II PSU
http://greisisworkbench.blogspot.com/2017/03/hi-here-is-my-design-for-c64-and-1541.html
https://www.youtube.com/watch?v=oY6ycn7qmzo

If you know of any others that’s not listed drop me a comment and I’ll update my list.


Some Retro Computing YouTube channels

December 30, 2021

It’s true to say that devotees of retro computing like myself are well supported for media content on the web. After visiting personal blogs and archive sites, YouTube is somewhere I like to find new content.

Below is a list of the YouTube retro computing channels I like to follow.

If you have a favourite channel that’s not listed drop me a comment and I’ll update my list.

The 8bit Guy (1.35M subscribers 274 videos 228,694,318 views)
https://www.youtube.com/user/adric22

RMC – The Cave (134K subscribers 339 videos 15,642,539 views)
https://www.youtube.com/c/RMCRetro

Jan Beta (43.6K subscribers 226 videos 4,823,519 views)
https://www.youtube.com/c/JanBeta

Adrians Digital Basement (121K subscribers 379 videos 19,672,489 views)
https://www.youtube.com/channel/UCE5dIscvDxrb7CD5uiJJOiw

Retro Recipes (112K subscribers 201 videos 10,067,350 views)
https://www.youtube.com/user/Perifractic

8-Bit Show And Tell (40.5K subscribers 121 videos 4,038,914 views)
https://www.youtube.com/channel/UC3gRBswFkuteshdwMZAQafQ

Noel’s Retro Lab (27.5K subscribers 113 videos 1,939,882 views)
https://www.youtube.com/channel/UC2-SP1bYi3ueKlVU7I75wFw

MindFlareRetro (12.2K subscribers 23 videos 230,434 views)
https://www.youtube.com/c/MindFlareRetro

retrobits (8.34K subscribers 49 videos 355,803 views)
https://www.youtube.com/c/retrobitstv

The 8-Bit Manshed (6.69K subscribers 398 videos 543,199 views)
https://www.youtube.com/c/BGOllie

Retro Tech Repair (4.01K subscribers 43 videos 165,016 views)
https://www.youtube.com/c/RetroTechRepair

The Retro Shed (3.54K subscribers 177 videos 215,003 views)
https://www.youtube.com/c/TheRetroShed

Arctic retro (3.42K subscribers 147 videos 325,814 views)
https://www.youtube.com/c/Arcticretro

TJ Ferreira (3.35K subscribers 610 videos 706,543 views)
https://www.youtube.com/user/MacSociety

TheRetroChannel (2.85K subscribers 62 videos 82,303 views)
https://www.youtube.com/c/TheRetroChannel

Retro Tech Ralph (2.54K subscribers 870 videos 671,005 views)
https://www.youtube.com/c/RetroTechRalph

ByteDelight (2.52K subscribers 364 videos 616,390 views)
https://www.youtube.com/c/ByteDelight/about

8Bit Retro ReFix (414 subscribers 50 videos 12,669 views)
https://www.youtube.com/c/8BitRetroReFix

DIYChris (373 subscribers 28 videos 17,705 views)
https://www.youtube.com/c/DIYChris/about

Retro Ruminations (280 subscribers 5 videos 31,572 views)
https://www.youtube.com/c/RetroRuminations

bitfixer (68 subscribers 5 videos 1,072 views)
https://www.youtube.com/channel/UC-bHBCI2JOCx95PAzoe-O8Q/featured


Elektor magazine is 60-years old this year.

November 30, 2021

I first encountered Elektor in the early 1980’s, probably around 1983. I remember going to our towns main library to read the latest edition (along with other electronic magazines of the time). I enjoyed reading it so much I would take out a subscription to it around 1986 and have been a subscriber ever since.

As well as Elektor I would also read Wireless World, Everyday Electronics, Practical Electronics, Electronics Today International and Electronics Magazine (from Maplin). I read all of them during those days and they definitely help educate me on electronics. I think I subscribed to most of them at one point or another. But one by one they stopped being published or merged and apart from Practical Electronics (which merged with Everyday Electronics) none of them exist today. Which is really sad.

Apart from being an avid reader of Elektor I also had the privilege of writing for the magazine on several occasions.

In 2005 I wrote three articles on the latest in microcontrollers, the arrival of the 32-bitters. In one these wrote about a design based on a NXP ARM and called it “ARMee”. I believe it was one of the very earliest articles, if not the first, on ARM microcontrollers to be published in a mainstream magazine.

The ARMee would go on to feature in other authors projects, a DCC model train controller project spings to mind. I would also go onto to write about the Raspberry Pi for the magazine.

The celebrate its 60th year, Elektor has published a special edition of the magazine which features articles about its 60 years and remembers many of the projects it published over the years. I very pleased to say my ARMee project got a mention on page 64.

The original ARMee article cam be found at

https://www.elektormagazine.com/magazine/elektor-200503/17921

Whilst the content of Elektor has changed with the times, it still features many quality and interesting articles and is still a great read. Here’s to another 60-years.