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Post your homebrew vintage like computer

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Zilogoz80

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Joined
Feb 26, 2008
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Hi, some of us beside collecting vintage computers, like to build or own computers, just like Steve Woz or Mr. Sinclair did one day, we still can get some discrete components and old processors like the Z80 or 6800 or maybe take parts from savaged old computers.

Attached is a picture of my home brew Z80 computer still only assembler programmable but I'm working on adding new functions, like a full functional keyboard and a display adapter.

Any body else want to post pictures, schematics, comments of their Homebrew Vintage like computer?
 

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Zilogoz80 said:
Hi, some of us beside collecting vintage computers, like to build or own computers, just like Steve Woz or Mr. Sinclair did one day, we still can get some discrete components and old processors like the Z80 or 6800 or maybe take parts from savaged old computers.

Attached is a picture of my home brew Z80 computer still only assembler programmable but I'm working on adding new functions, like a full functional keyboard and a display adapter.

Any body else want to post pictures, schematics, comments of their Homebrew Vintage like computer?
Click to expand...
----
Very nice indeed! How'd you make/where'd you get the PCBs?
I've still got some Z80 CPUs & support chips if anybody needs any.

mike
 
MikeS said:
----
Very nice indeed! How'd you make/where'd you get the PCBs?
I've still got some Z80 CPUs & support chips if anybody needs any.

mike
Click to expand...

Well I designed the PCB's using an old software...you need a DOS simulator to run it in today's computers, the schematic was designed using ORCAD 4.0, all files were converted to DXF and ploted with Autocad at a scale 1:1, with this I got the PCB made when I was living in South America, it was very cheap I paid something like U$65 for both cards, the big one is almost letter size, it has silk screen, solder mask, is double side and through plated hole, well it was like 10 years ago...
 
Wow! That's a very nice little computer you've got there :D

Mine is here http://kaput.retroarchive.org

Gene Buckle kindly offered me hosting on his server after he posted a link to the ClassicCmp mailing list to my server, which is hosted on a 256/64k BIT internet connection.

My next project, which is coming along nicely, is a Z80 SBC which is wire wrapped on a punch-down wire wrap prototype board. When it's done it should run MP/M II, a TCP/IP stack, and have a video controller supporting 80x24 text and a 320x200x8bit graphics mode. I've got a Bt453 palette controller which will complement the 256 colour graphics mode. It allows for a 24-bit palette, 8-bits per primary colour, and 75 ohm output which is compatible with VGA monitors. I'll use a 6845 to control the timing.

Pictures:
http://kaput.retroarchive.org/pictures/z80_1.jpg
http://kaput.retroarchive.org/pictures/z80_2.jpg

edit: Forgot to mention I'll probably put an Atmel AVR of some sort into the video section (which will probably make it more powerful than the Z80 controlling it) for 2D sprite acceleration.
 
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Hi All,

This is a subject near and dear to my heart. Last year I built a completely homebrew Z80 ECB based computer from protoboards. It worked OK but the construction technique (point to point wiring aka rats nest) makes working on it unpleasant.

So after a bit of doing other things, I am getting the itch again to build another homebrew computer from scratch. However this time to make my own PCBs rather than the rats nest wiring.

There is a free CAD program for building electronics called Kicad I have been using from here

http://www.lis.inpg.fr/realise_au_lis/kicad/

to layout a "simple" Z80 SBC circuit from here

http://z80.info/gfx/z80test.gif

It comes with some simple test software available on the website.

The purpose is to proof out the making PCBs, and is intended to be an intermediate step towards a more complete Z80 project. My plan is to print the PCB circuit on a laser printer and transfer it to a blank board using an etch solution.

I have the schematic entered into kicad and started on the PCB layout but am having some problems with the PCB layout. First, not all the parts are recognised by the PCB layout program and second the auto routing seems to not be working.

Is anyone interested in a little Z80 SBC project with make your own PCBs? It seems like there are people here with some experience in these matters. If anyone is interested, I can post my work so far and maybe there are others who can tweak it. I'd really appreciate some help with the PCB layout.

Hey, its just an idea but maybe some others would like to build their own Z80 computer from scratch. It is a *lot* of fun.

Thanks!

Andrew Lynch

PS, I uploaded zip file of my TP2.zip project in case anyone is interested. Let me know what you'd like to do. Thanks!
 
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That's too awesome. I know sitting at home having the knowledge on this stuff in books doesn't actually help me magically absorb the information but I really hope someday I can figure all that out and build something homebrew too. I mean, that's actually partially what got me into collecting in the first place since all the wiring is big enough to look at if I actually sat down to figure out how all the parts work it would explain the wiring better.

I'd love to build a pcb project from scratch. There is someone here in Austin with The Robot Group who does small pcbs by hand in his kitchen although they just tried out one or two services that you recreate the circuit using their (proprietary?) software (it's tedious and non-standard) but they were able to get 2 or 4 of one small design made for around $60 and they don't charge per device (some companies evidentally will charge you more if they can tell you're going to cut it into multiple units on that one board). I can post the company or PM it if anyone is interested. Actually just PM me if you want the info since I don't want this to be a sales pitch forum.

I know not many people have the experience and although I can barely scrape by with pretending to know how some of that works you may remember me sitting there at the end of your class at the last VCF scrambling to finish soldering the MicroKim before the museum locked us all out lol. Still, I have an interest in anything since I missed out on that opportunity when I was younger. I was just excited the Kim worked after all my less than fancy soldering, I honestly thought I was going to have to go back through and fix some cold solder joints or some of my burn marks (character) that I had on there.

I know there are some Sim-1/Kim-1 type schematics out there as far as a home brew project although I think I remember you saying atleast one of the more common ones had an error which would probably throw me off without realizing it.

One of these days when I get the workbench cleared off again (i.e. move a few vintage systems off of it) I'll complete the other kits I have (ZX-80, Replica-1, AltairKit, Kenbak replica kit). I admit though completing the MicroKim was a huge boost to my ego (yet to be determined if this is good or bad ;o) ) as far as my ability to solder things and built a kit or repair something on a smaller level. I'd only really done minimal desoldering and component replacement before that, never sat down for 4 hours and soldered everything like that which was one of the best experiences I've ever been able to have.

Sorry.. accidental rant (got excited) there,
- John
 
I am also dreaming about making my own homebrewn microcomputer too... But I am only 16 years old and I got a lot of schoolwork, so I don't actually have the time or experience to start such a project.

Do you have any suggestion about good reference books explaining how to make your own computer systems? The only books I got at this time is the "iAPX 86/88 users manual, July 1981" and "The IBM PC from the inside out, including the AT" (the last one doesn't really go in detail about how a computer system is buildt up, but it explains breefly how they're put together).

*Edit*
Fixed some typing errors.
 
Well, as for a homebrew computer my *opinion* is that the most difficult part is finding a decent board to build it on. A fully designed PCB would help tremendously. Using protoboards can work depending on the techniques used. Wirewrapping is good but point to point wiring is more reliable. Either way you end up with a big mess of wires you have to deal with.

If you are interested in a bus based design, then things get really difficult. You'll need a prototype board with an edge connector or a prototype board you can attach a bus connector to like Thrashbarg and I did.

My recommendation is to do a simple Z80 SBC using commonly available 22/44 edge connectors. That or the ECB is good. S-100 is too complex and has strange power requirements although it is doable and the prototype board *are* available but expensive.

There is another great design called the S-44 simple homebrew computer. I have a zip file of the webpage around here someplace. I can send it to anyone who requests it as it is 2+ MB in length. It is about as simple a design as possible and uses a simple IO bus design based on 22/44 edge connectors. It even comes with a simple monitor program you can burn into EPROM.

Thanks and have a nice day!

Andrew Lynch
 
Hi
I can't think of a computer that I built from scratch as a hobby
but I have made several Z80 and 8051 embedded computers
for a previous employer.
The closest I've come is what I called "the single board computer".
It can be seen in the picture to my left:

http://www.vintage.org/exhibit99/VCF_3.0_Dwight_Elvey_Exhibit.jpg

It was built on a single ply wood board. I used a NC4000 processor
board that had a few modifications to bootstrap from ROM and then
switch to all RAM.
I built my own expansion ROM board to bring the system to 64K words
( 16 bit ). Also added were a floppy controller and a HD controller
form XT vintage PCs. The HD was a 5Meg ST506.
I wrote my own low level drivers for the floppy and HD controller
from scratch and old spec sheets.
It all ran under CMForth.
The RAM board had a parallel port added. I used this to print to
a printer for listings and also to connect one of those cheap 2716
programmers to. I could completely recompile the ROM images
in about 5 seconds, using the HD. That 4MHz NC4000 was
truly fast!!!
For those that are curious, the unit to the right of me is an Intel mcs4
development system( 4004 ). It is operational and can program 1702A's.
There are better pictures of this unit on the web.
Dwight
 
PER - Maybe you could build one like mine. It's only a few chips (a microcontroller + serial EEPROM), and a serial LCD.

Behold, my DIY laptop! http://www.chrisfenton.com

(This one even made it on slashdot!)
 
Amazing

Amazing

All works posted so far are really impresive, what amaze me more is how many different concepts can be brought to life even using same processors, chips etc. As some previous posts said, Vintage computer collecting is a hobby close related to the hobby of electronics, some times we have to fix or do some tweaking with the old machines we collect, but building your own from scratch really opens you to a whole new understanding of some of the many problems these engineers faced back in the earlly 70's.

Keep up the good work, and for those who want to start their home brew systems from scratch, there is a lot of resources on the net; there was never and easiest time to start on this hobby and in this forums many of us are willing to help as well. :D
 
The more I've started to dabble in electronics (as a resut of havening to fix my old iron) the more I respect those who actually understand this stuff. The science of it blows me away.

Great projects!
 
per said:
that would be a good start :) . Anyway:rolleyes:, my goal is to make a more advanced system with a microporcessor and manually DMA switches/LEDs.
Click to expand...

Hi
One could look at the schematic for the Atari pinball machines.
They used DMA for the lights and input switches.
It used a 6800 for the processor.
The DMA always made these a little harder to fix compared
to the direct access I/O like was done on the Bally pinball
machines.
Dwight
 
Zilogoz80 said:
Hi, some of us beside collecting vintage computers, like to build or own computers, just like Steve Woz or Mr. Sinclair did one day, we still can get some discrete components and old processors like the Z80 or 6800 or maybe take parts from savaged old computers.

Attached is a picture of my home brew Z80 computer still only assembler programmable but I'm working on adding new functions, like a full functional keyboard and a display adapter.

Any body else want to post pictures, schematics, comments of their Homebrew Vintage like computer?
Click to expand...

Hi!

I am currently using KiCad which is a free electronic design tool for schematics and PCB design. As the starter project, I am entering in the design from my old "Test Prototype" Z80 home brew computer I built last year. The design is not exactly the same but pretty similar:

Z80 CPU
8255 PPI
16550 UART
512K bank switched SRAM
1M bank switched ROM (new, was 32K EEPROM)
DS1302 RTC (pins for battery backup)
Standard ECB layout (100x160 mm)
DIN 41612 ECB connector with standard pinout
Uses standard AT/ATX drive connector type power supply.

My plan is to get the design entered and refined for both the schematic and the PCB layout. Then use the freerouting.com tool to autoroute the board.

The PCB is not overly complex but it has enough on it to pretty much fill the board. Getting the autorouter to come to a solution is starting to be a problem so I think I am at the practical limit for what can be added to it.

I am not a professional PCB designer so if there are some experienced designer/builders out there who'd be willing to review my design for improvements, I would certainly appreciate it a whole bunch. Please PM or email me for the files.

Eventually, I am going to get some prototype PCBs made and I have a few ideas as to where to go for that. Here is my list of low cost prototype PCB makers:

https://www.barebonespcb.com/!BB1.asp

http://olimex.com/pcb/pcb-doubleside.html

The first PCB costs about $53 plus shipping. Additional PCBs really drop the price considerably. The second PCB unit cost is about $32 and for four PCBs the unit cost drops to $22 plus shipping. Of course, that does not include any parts.

If anyone is interested in joining me in a "build it yourself from scratch" Z80 computer project, please let me know. This may be your opportunity! In my experience the most difficult part is the PCB.

Using prototype boards for wire wrap or point to point soldering each have their strengths and weaknesses however both approaches are plagued by overly complex wiring and debug procedures.

A ready made PCB should dramatically reduce build and debug complexity, assuming I can get it to work. There are no guarrantees in that department! As a result, this project is probably not suitable for total newbies and assumes some basic electronic familiarity and design principles. Of course, having parts and basic test equipment (soldering iron and VOM at minimum, logic probe and oscilloscope would help too).

At any rate, I am still ALPACA mailing list and this topic is probably more appropriate there. If anyone wants the schematic, netlist, PCB layout, just let me know. The whole thing is in flux at the moment so it will definitely change before the final PCB design is sent to the manufacturer.

Thanks!

Andrew Lynch

PS, I made some PDF prints of the design so far but cannot attach them to this message due to file size limits.
 
Andrew,

As to the autoroute problem, having used several PCB design packages, I've found that, if you delete the traces from a couple of points around one you're having trouble with, manually route the trace, then autoroute again, it will clean up the one you were having trouble with and re-route the deleted ones.

HTH
 
Hi Richard,

Thanks for the advice! I will give that a try. So far, I have been reorganizing the PCB layout to help the autorouter along. Grouping like functions together, minimizing long connections, etc. It is kind of like cleaning up an old crusty program.

With the latest PCB version, it now completes autorouting in a semi-reasonable time. Now the optimizer is running on it to try and reduce the trace length and via count.

The ECB card format is rather tight to work with and the chip count really is not that high but the density is high enough to make for the traces being really packed in there.

I have a few trouble spots like around the parallel IO chip and port. Watching the autorouter place the traces and seeing it struggle in spots really gives me a lot of insight as to where my design needs work.

This really has been fun working on the project. KiCad has really matured and the latest developments with freerouting.com have really taken it to a new level.

Best of luck and thanks!

Andrew Lynch
 
Andrew,

Sounds like a great project you're designing. I know that I would be interested in building a home brew computer based on the specs you gave above.

Keep up the good work!

Howard
 
Hi,
I started a new thread over in "other".

The PCB is in the autorouter now finishing its trace optimization. I am going to go through the whole design again start to finish and compare it against my working Test Prototype. Odds are some errors have crept in.

If you are interested you may want to switch to the other thread as I sort of changed topics on this one.

Thanks!

Andrew Lynch
 
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