wtb: 68020 minimal board - Page 1
Forum section: electronics / general

author: DiTBho
author_rank: Super Contributor
timestamp: June 21, 2023, 02:39:57 pm
content: HiI d like to play with a 68020 minimal board, with just- static ram, 512kbyte is enough- uv eprom, 256kbyte is enough- 1 or 2 rs232 serial linesEverything extra is premium.If there is no firmware in the rom, no problem I will develop and burn my own into the eprom.If you have one for sale, I am interested.(Personal hobby)

author: Leo Bodnar
author_rank: Frequent Contributor
timestamp: June 27, 2023, 09:14:48 pm
content: A lot of HP instruments from 1990-s are running HP-UX on 68k series MCUsPerhaps an old isntrument that has service manual is a good start?

author: globoy
author_rank: Frequent Contributor
timestamp: June 27, 2023, 10:01:00 pm
content: How about some old Mac motherboard. I think there were several that used 68020 or 68030 processors. You could replace the Apple EEPROMs with your own. I'll bet there is plenty of documentation showing the addresses of various peripherals.

author: DiTBho
author_rank: Super Contributor
timestamp: June 28, 2023, 06:21:26 am
content: Quote from: globoy on June 27, 2023, 10:01:00 pmYears ago, I hacked an Apple LC475, replaced 4 ROMs, and replaced the MC68LC040 CPU with a smart socket able to adapt the MC68060 CPU to the pinout and voltage of the 040 CPU interface on the motherboard, so I ended up integrating 060BSP, Linux, and ... again another GNU/Linux machine.Now I am looking for something smaller, more compact, with just ram, rom, serial, like eval boards made in the 90s for Coldfire.Quote from: globoy on June 27, 2023, 10:01:00 pmMy primary source of information was the Linux kernel source and the "Emile" bootloader source.

author: DiTBho
author_rank: Super Contributor
timestamp: June 28, 2023, 06:22:00 am
content: Quote from: Leo Bodnar on June 27, 2023, 09:14:48 pmWhich one?

author: DiTBho
author_rank: Super Contributor
timestamp: July 04, 2023, 06:57:43 pm
content: umm? anyone?

author: KE5FX
author_rank: Super Contributor
timestamp: July 04, 2023, 08:21:43 pm
content: The 71450A/71451A optical spectrum analyzers come to mind, as do the 54520/54540-series scopes. Also at least some of the9000-series computers.I believe the 89410A family of VSAs used the 68020 as well, but am not 100% sure.

author: bingo600
author_rank: Super Contributor
timestamp: July 05, 2023, 06:31:09 pm
content: If you can live with a 68030 & uclinuxhttp://www.kdvelectronics.eu/uClinux-cisco2500/uClinux-cisco2500.htmlSearch ebay Cisco 2500https://www.ebay.com/itm/303702068264https://www.ebay.com/itm/284361345371If you want to play w. ethernet get an AUI Transceiver toohttps://www.ebay.com/itm/115815723857They do come with different flash sizes , and the flash addon board is prob "Unobtanium" or crazy expensive.I lost count of how many of these i have scrapped .../Bingo

author: globoy
author_rank: Frequent Contributor
timestamp: July 05, 2023, 06:47:01 pm
content: Have you looked at github to see if anyone published a design you could build for yourself?I did a super quick search and found:https://github.com/THemmecke/68K20Or maybe some old VME board?

author: DiTBho
author_rank: Super Contributor
timestamp: July 07, 2023, 07:55:19 am
content: Quote from: globoy on July 05, 2023, 06:47:01 pm"super quick search"I think "quick" is the point: I could possibly also design my own board with KiCAD or EagleCAD for a super simple and minimal SBC { CPU, static RAM, voltage level shifter, {bus arbitrer, serials, PIT} on FPGA }, just ... I would avoid to invest more time in this, looking for components (68020? 68020-socket? from Surplus reseller? From some Recycler in China? mumble ...), fixing mistakes on the PCB (2 layers? would it be fine enough? 25Mhz? good signal integrity?) ...When I started this micro hobby business, I had 50 hours scheduled, and guess what? 500 hours later I'm still fixing x86 stuff (both hardware and software) that doesn't work right or that I don't like on my Soekris routerQuoteI would avoid GNU/Linux on m68k, it's tool slow!I know it from my previous project: gcc-v4.1.2 on GNU/Linux kernel v4 on Apple LC475/m68060@25Mhz (with 060SP) takes more than 25sec!!! to compile a simple hAllo.cCode:#include <stdio.h>int main(){printf("hAllo!\n");return 0;}(gcc hallo.c -o hallo ... on my MIPS laptop @ 800Mhz takes 0.3 sec,I'm sure on a modern RPI-v4 it would take even less time .. )I'd like to support something different, like { ucMON, ucOS/2, XINU, ... }Quote from: globoy on July 05, 2023, 06:47:01 pmVME boards are nice but look ***very*** expensive on eBay, and they are complex to hack and setup.From a job i did for a client, i brought home the control board of an industrial sewing machine, it's a dual 68060@50Mhz CPU VME board running VxWorks v5.It's damaged (DRAM test fails), I think I can repair, but it's *** very *** complex! CPUs talk on a small shared ram (2Kbyte), and it's the simplest part, you have hardware mailboxes on chip, and four large ASIC chips controlling the bus, the dynamic ram, timers, ethernet (ethercat), four RS422, ... and an industrial dedicated bus.Those ASIC chips are nothing but memory mapped registers to be read and written, a piece of cake very easy, unfortunately their documentation is not very clear from the BSP up (the BSP is designed to hide low-level details, so it exposes those registers as function() to be invoked from your { C, ADA } application), and since they are ASIC industrial stuff, you probably only have the documentation if you bought the complete package, which makes them not very much on the net.Unless a bunch of hobbyists have bothered to support the card, like the VMEs used by OpenBSD, NetBSD, ...Sure, all these parts have a BSP, but ... it's comes from VxWorks support and it's closed software, so ... tecnically I could ask for sources, and bring them home and re-use them for writing my own minimal BSP and drivers for my hobby stuff.Anyway, just to power the VME board and take out a serial console, you have to build a backplane to power the card from the two large 96-pins (3x32pins) connectors on the back of the board, typical of the rack industrial boards.I have a mezzanine backplane at home with PSU lanes { +5V, -5V, +12V, -12V, PowerGood, SysReset }, all to be rapaired.Ummm