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Interested in a home brew Z80 computer project?

is there a list of part that are needed to build a z80 because i want to build one but i don't want to spend alot of money and i am hopeing i can scavenge most it if not all from old motherboards. thanks
 
wolfie said:
is there a list of part that are needed to build a z80 because i want to build one but i don't want to spend alot of money and i am hopeing i can scavenge most it if not all from old motherboards. thanks
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I take it you're not talking about the N8VEM, in which case we could split this off into a new thread if necessary.

The bare minimum would be the Z80 CPU itself, some memory and an oscillator to use as a clock. Some kind of I/O is nice if you want to see what it's doing - this could be as simple as some LEDs and/or switches.

You might be able to scavenge an old flash BIOS chip to use as ROM, maybe the cache from a 486 motherboard could work as RAM. The Z80 and an oscillator can be found on some kinds of expansion cards.

Then you're got the small point of actually designing your computer ;-) You'll also need something to wire it all up on, like a bread board or some other kind of prototyping board for soldering or wire wrapping.
 
I don't think you will get many parts from old motherboards. Unless they are vintage motherboards, in which case, pls pls, stop right now!

I built a couple of Z80 computers in the last week. Takes about half an hour to solder a board up once you have the components. Realistic cost is about $60 per board - can you afford that?
 
wolfie said:
is there a list of part that are needed to build a z80 because i want to build one but i don't want to spend alot of money and i am hopeing i can scavenge most it if not all from old motherboards. thanks
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Hi! Yes, there are parts lists and BOMs for all the N8VEM designs on the wiki. Also schematics, hardware design information, software, PCB layouts, Gerber files, KiCAD and Eagle EDA files, stories, notes, builder dialogs, questions, answers, pretty much any sort of information you can think of is there already. It is all freely available for builder use.

I highly encourage you to use scrap electronics for parts. Using scrap is a triple win; you save lots of money and it makes the build more enjoyable (I think) and you keep perfectly good working components out of the waste electronics stream. Lots of old electronic components contain elements which are perfectly safe in a working system but are toxic and dangerous when left outside in the elements to degrade. Certainly reusing scrap electronics is a better and more responsible thing than sending it to some pitiful third world person poison themselves and everyone else by burning it in an open pit for scrap metals.

The N8VEM parts are mostly common 74LSxxx TTL and there is a lot of flexibility for parts substitution. You can find ICs and components in a variety of places ranging from old PCs to various scrap electronics. I have recycled a *lot* of components that way. Old controllers, cash registers, consumer electronics, broken toys, random ISA boards (broken of course). Old PCs are great too but that's almost too easy a target. Go after something more challenging!

There are several techniques for extracting used ICs and components from old boards. You'll find many of the ICs you'd need on practically any old PCB from the early 1980's although I don't recommend trashing vintage computers there are plenty of other parts donors out there if you are willing to dig into anything with a circuit board.

8255, 16550, 74ls245, 74ls08, 74ls10, 74ls32, resistors, capacitors, connectors, etc are all very commonly available parts. You can find them at surplus stores or even electronic scrap yards. Depending on how adventuresome you are I recommend getting a chip tester or at least one working unit for part substitution to help sort out the good from the bad.

Believe me, you won't be the first N8VEM builder to go down this path! Just join mailing list and wiki and post lots of questions and tell us all about your progress!

There are lots of exciting things happening right now. Work continues on the FDC CBIOS issue although we've kind of taken a little break to work on the PropIO board. Last night was a big event; I am building a prototype of the PropIO along with Dave (Yoda) the PropIO designer. Here are some photos of last nights results:

http://groups.google.com/group/n8ve...cb07e94b794b4ff4?show_docid=cb07e94b794b4ff4#

I am not sure what's next. I am thinking since we made such great progress on the PropIO that Dave probably needs some time to digest the next steps. The plan is to get the PropIO uSD socket working and write a CBIOS to use those itty bitty uSD cards to work as mega sized CP/M hard drives. There is already a CBIOS that uses the PropIO PS/2 keyboard and VGA display.

While that project is "soaking" I think I am going to write a floppy disk test routine extension to the FDC monitor program that Dan, another N8VEM builder, wrote recently. I added a floppy disk formatting routine and it works fine although I am curious to see how many builders are able to use the floppy drive subsystem and how reliable it is.

So there is a lot happening on the N8VEM home brew computing project. Please join us if you are interested. There is always room for more exciting builder projects and neat stuff to do. James and the Propeller fans are a veritable fountain of cool and wonderous projects. I can't keep up with the developments there are so many and so often!

Thanks and have a nice day!

Andrew Lynch
 
Dr_Acula said:
I don't think you will get many parts from old motherboards. Unless they are vintage motherboards, in which case, pls pls, stop right now!

I built a couple of Z80 computers in the last week. Takes about half an hour to solder a board up once you have the components. Realistic cost is about $60 per board - can you afford that?
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i was thinking about using some 486 motherboards for parts. i know where there are a few that look on the older side. i was also thinking about taking some parts out of a sega genisis if i can. at this moment in time i cannot afford $60. my projects are always longterm. i've had a truck 2 years and its still not on the road.
 
Wolfie: Maybe you can buy an old, ready built Z80 computer, take it apart in parts and solder everything back in again? :p You should easily be able to get some simple Z80 computer for less than $60.
 
Hi! Yes, if you look around you can probably find old electronics with Z80 boards already in them. Its amazing what you can find in a scrap yard or dump. Generic Z80 scrap boards go on sale on eBay frequently although that rather defeats the purpose of scrounging around.

Thanks and have a nice day!

Andrew Lynch
 
carlsson said:
Wolfie: Maybe you can buy an old, ready built Z80 computer, take it apart in parts and solder everything back in again? :p You should easily be able to get some simple Z80 computer for less than $60.
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i want to start collecting parts and build my own till i can afford to buy one.
 
Hi! You may want to investigate the minimalist approach to building an SBC.

Here is a stripped down minimum parts list just to get something up and running for an N8VEM SBC.

http://n8vem-sbc.pbworks.com/Least-expensive-but-still-functional-N8VEM-SBC

You can probably do some parts substitution and shrink this down even further. Use the Gerber files and make your own PCB to save even more using toner transfer method.

There are lots of things you can do to get the costs down.

Thanks and have a nice day!

Andrew Lynch
 
thanks Andrew for the link. That was exactly what i was looking for. i have only 1 question now and that is what is X1 CRYSTAL. i think i can find the rest. if you could point me to some pictures or info that would appreciated.
thanks again
mat
 
There are two crystals and they are both 14 pin modules. Only a couple of dollars from futurlec or many other places. The 4Mhz one is the main clock and you can run a range of frequencies - eg I underclock mine at 3.68Mhz because I have a few of those modules lying around. The 1.8432 Mhz module does need to be this frequency though as this runs the UART which sets the baud rate. The modules have 4 pins but they fit into a 14 pin socket so that makes it easy to change clock frequencies if you want to down the track.

If you were feeling keen there are clock circuits using discrete xtals and a few gates from a 74LS04.
 
wolfie said:
thanks Andrew for the link. That was exactly what i was looking for. i have only 1 question now and that is what is X1 CRYSTAL. i think i can find the rest. if you could point me to some pictures or info that would appreciated.
thanks again
mat
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Hi! Thanks! James is right, there are 2 main oscillators; the UART (1.832MHz) and CPU clock (typically 4 MHz but can be practically anything).

There is also another crystal X1 for the realtime clock. It is 32768 Hz and not needed in the absolute minimum build without the RTC.

Thanks and have a nice day!

Andrew Lynch
 
Yes, Andrew is right, that is a real time clock crystal. You can leave out that part of the circuit if you like.

I've got some photos of a recent build of a modified N8VEM that has a few extra features. http://www.smarthome.viviti.com/build

Things are changing all the time with this project so if you are interested please join in the fun!
 
Great Googly Moogly! Where did *THAT* come from? Wow!

James, I am impressed! Did you post that write up before and I am just now finding it? Geez, I need to crawl out from under my rock more often.

That's one thing about the N8VEM home brew computing project, you never know what will happen next! You made my day!

Thanks! Have a nice day!

Andrew Lynch
 
Hi! It is an oblique reference to a very funny football (US) related TV commercial. The grounds keeper has just finished laying out the chalk lines and field graphics of the Kansas City Chiefs. After all that work, he looks over and sees he has spelled out the Kansas City Chefs. The look on the poor guys face is priceless.

http://www.youtube.com/watch?v=hSAXLayoMKI

Yep, I know the feeling.

Thanks and have nice day!

Andrew Lynch
 
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