Osirix - Motorola 68000 Homebrew computer and OS

[AMenard]

Hi!

Long time lurker, but I'm finally getting ready to start on my pet project. I'm in the planning stage of designing and building my very own homebrew computer. The projected spec are the following:

[*]CPU: Motorola 68000
[*]RAM: 4 Meg
[*]I/O: Serial, PS/2 connector for key and mouse
[*]Video: Arduino based VGA video interface. Here is an example of one:https://dqydj.com/how-to-produce-640x48 ... n-arduino/
[*]Audio: 4 voice PCM (Paula chip from a dead Amiga 500) and/or a C64 SID chip (Why not!)
[*](3x) Expansion slot for more ram (up to 12 meg more), Compact flash "Hard Disk", Game Controler, extra I/O

For the OS I'm going for a "simple" Assembler/Monitor type shell at first. Something I can boot into, load or type in program and run them. It will be loaded from eeprom. This should be enough for a start. I'm using both an Amiga 1000 and Cloanto Amiga Forever emulator on PC as a development plateform (Asm-One and Aztec C) and I have an eeprom programmer to "burn" the chip.

This isn't something I'm in a hurry to do. I'm at the end of my carreer in IT and this will be one of my hobby for the next couple (many) year. I always wanted to build my own computer, like the pioneer in this field of technology. I even started to work on one, based on TTL chip, when I was in my teens. Now that I have the time, and the money, I can get back to it.

Don't expect a day to day log from me, but I'll post how it goes when I can.

[Ycep]

How's it going?

[Ycep]

Creating computers by yourself on kitchen table may get pretty dirty. You may buy two resistors, put them in and later decide to remove them and add another ones, know that stuff.
I'm not sure how are you going to make Motorola 68000 series CPU in your homebrew computer. But, okay, if you work on it 8 hours a day within 2-3 months you may make instruction INC, DEC, ADD, SUB and MOV work.
If you make all your planned stuff actually work (hard disk, expansion slots, etc.), bravo. New Stiv Džobs.

[Sik]

*blinks* Just get an actual 68000? I just did a quick search and they don't seem to be that hard to find (I even found somebody selling chips to make your own Atari ST... huh o.O) Or get a 68000 core for use in a FPGA.

Also the 68000 doesn't have INC/DEC. It has ADDQ/SUBQ which is similar except they can add/substract any value from 1 to 8.

[Schol-R-LEA]

I'm not sure how are you going to make Motorola 68000 series CPU in your homebrew computer.

I am pretty sure that AMenard is building a SBC which uses a Motorola 68000 chip as its CPU, rather than implementing a CPU with that architecture using TTL hardware.

I am also pretty sure you knew that, and are just making a joke, but whatev'.

[AMenard]

I'm not sure how are you going to make Motorola 68000 series CPU in your homebrew computer.

I am pretty sure that AMenard is building a SBC which uses a Motorola 68000 chip as its CPU, rather than implementing a CPU with that architecture using TTL hardware.

I am also pretty sure you knew that, and are just making a joke, but whatev'.

Exactly... English isn't my first language (frenchy here) so maybe I wasn't clear enough. I should have writen "Motorola 68000 based Homebrew computer and OS"

I'm presently at the design and part picking stage working in KiCad and ltSpice. I've just received my two 68k assembler book that I won on eBay so I can freshen up on that subject. I also received my eeprom programmer. I'm also considering basing it on the 68010 so I can implement virtual memory in my supporting OS more easily. I could also move to the 32bit 68020 but the PGA package is less breadboard friendly...

And what I'm doing isn't all that fantastic. A quick search on Google will result in quite a few completed project.

And keep in mind that I'm 51 years old and at the tail end of my tech career. I have 7 years left at my present job before being eligible for my full pension. This will be my retirement project. Some likes to play golf, I like to build things

[Schol-R-LEA]

Well, I suppose if you aren't inclined to build sailboats in your basement, with only hand tools, until you have a small fleet which could sail off on the sea of coffee and Gentleman Jack bourbon you drank while doing it (well, except the one named after your third wife which you burned after the divorce...), then this is a good alternative.

[AMenard]

Well, I suppose if you aren't inclined to build sailboats in your basement, with only hand tools, until you have a small fleet which could sail off on the sea of coffee and Gentleman Jack bourbon you drank while doing it (well, except the one named after your third wife which you burned after the divorce...), then this is a good alternative.

So... You're a fan of NCIS I guess

[Schol-R-LEA]

Meh, I've watched it, and it is better than a lot of other series. My father used to watch it quite often, so I would too when I was staying with him (long story), and while I like it well enough, I don't normally go out of my way to do so now. I don't think I've watched it more than two or three times after he died last year.

[AMenard]

No biggy... I was going by the sail boat in basement statement.
Personaly I'm more of a Criminal Minds type of guy.

In any case, I'm still studying and designing the hardware taking into account what my OS will have to support and how to do program it to do it adequately since I wan't it to be rom based.

[jojo]

I just did a quick search and they don't seem to be that hard to find

Harder than it used to be, unfortunately. Just a couple of years ago I ordered two or three HD68HC000P10s off of Digikey or Mouser or Jameco or some such for a pretty good price that I was going to do an SBC around myself. Unfortunately I lost all but one in a move and I just accidentally blew up the last one a couple of weekends back. Went looking to buy some replacements after that, and it turns out ain't nobody sell DIP64 68ks anymore except for Chinese and Bulgarian suppliers on eBay. You can get the QFPs on Mouser, but they're non-stock items.

[AMenard]

I just did a quick search and they don't seem to be that hard to find

Harder than it used to be, unfortunately. Just a couple of years ago I ordered two or three HD68HC000P10s off of Digikey or Mouser or Jameco or some such for a pretty good price that I was going to do an SBC around myself. Unfortunately I lost all but one in a move and I just accidentally blew up the last one a couple of weekends back. Went looking to buy some replacements after that, and it turns out ain't nobody sell DIP64 68ks anymore except for Chinese and Bulgarian suppliers on eBay. You can get the QFPs on Mouser, but they're non-stock items.

You can also scavenge them from old devices. Millions of game consoles were using the MC68000 as their CPUs. Or you can buy a used and broken Amiga and canibalize it.

[AMenard]

Hi,

Just to let the community know that this project isn't dead and I'm still in the design phase. Like I said, I'm under no presure to finish it as it's a personnal project, not for a job. I'm also learning Kicad at the moment. I've got the schematics part of kicad under control, now I've got to learn how to generate a PCB from it. The architecture isn't set in stone either. I see so many possibility with different "retro" CPUs. I've also been thinkering with audio/video circuitry lately so these can also evolve to something else.

I'm also trying to settle on a single Linux distro for my dev workstation. I'm a bit of a distro-hopping-olic and waste so much time reinstalling my system. I used to love Antergos but it's a mess right now with the installer crapping all over the place. I'll try Manjaro tonight and see how it goes. I prefer Arch based, but could also live with Ubuntu/Debian based distro.

Finally, I'm catching up on reading about OS design and general programming and taking notes of what I want Osirix to achieve, eliminating impossible goals in the process ( I won't be creating something as big as Linux or Windows all by myself). But I'm still going for a builtin ASM/Monitor type with the possibility of loading a more complete "DOS" from it or by holding a key while booting, kind of like an Apple II back in the day.

My main goal is to have fun while doing it, nothing more.

[iansjack]

Great choice of processor.

£7 on eBay: https://www.ebay.co.uk/itm/Motorola-MC6 ... SwybpbpkZR

[AMenard]

Great choice of processor.

£7 on eBay: https://www.ebay.co.uk/itm/Motorola-MC6 ... SwybpbpkZR

I have 5 of those already

I repair retro computer as a hobby. I had a batch of Amiga 2000 and 500+ with leaking battery that damaged the board beyond repair. I was able to save the 68000 from those and from an Atari 520STfm that was damaged during shipping from Greece (something fell on it and cracked both the case and the PCB). I also have two 65C02 from some defunct Apple IIe and two 6510 from a couple of burned out C64. I ordered a couple of Z80 (brand new!) since I've found a nice project for those while researching for my homebrew computer. I may also get a couple of Intel 808x just for the sake of completness

As long as it's a DIP I can still solder it with my 53years old eyes. I may need a PCB oven for surface mounted devices.