Homebrew Z80

[Sasha]

Check out this insane PCB wiring.  :o

[Goblinz]

Wow... Spaghetti Junction! Not sure if troubleshooting would be easy or hard on this thing. Any chance that you could post the link for this?

[Sasha]

OOps. I thought I did. Here it is: http://www.hanssummers.com/computers/newz80/

[stryd_one]

LOL. Impressive, yet, crazy :D

[Sasha]

It look more like art installation than real PCB.  :)

[madox]

That's pretty damn cool. Not easy to design that way.

[/tilted/]

The dude is crazy. I love it.

I especially love the bit where, rather than be boring and transfer basic ROM things like the character set and keyboard driver from a built computer, he built a bit-by-bit switch setup, allowing him to enter these by selecting the address line, and entering the data, all using switches.

Hardcore.

this guy is seriously my new hero.

[TheAncientOne]

One of my old industrial customers have a computer contolled circular sawing machine, called a Wadkin TT14. You entered a cutting list onto a teletype, and then put long planks on an input conveyor, and it worked out the best cuts per length and cut them.

The Processor was a Texas Instruments TI960 minicomputer. To load up the operating system and software you had to first enter a short series  series of programs on front panel switches. You cleared and initialised the memory, started a tape loader, loaded the hight speed tape interface software, then the operating system, (from a punched tape!), called PAM-D, then finally a huge tape with the saw program on it. There were some patches to the main program that had to be input by hand after that. With what I know now, I would probably have re-dumped the tape with the patches installed. At one time I had to buy in an Old Remex tape reader and punch (still got it too), and re-duplicate the tape because they were getting worn out.

As you say: real hardcore computing, and kind of cool too. Though perhaps not This Hardcore:

They didn't take my advice to buy spares and docs for the computer when it went 'end of life', later I had to repair it twice with no docs. First time 4 bits of register went out - and a I managed to trace that to a failed 7489 memory chip, ( Bipolar RAM, 16 x 4 bits,it used 4 of these for it's main 16 bit registers - wow!). Second repair took me over a month: I had to make my own extender cards, buy and scrounge spares and design my own fault finding tools.

Sadly I've no pictures from that era, though if anyone ever needs a backup tape of PAM-D, I kept one just in case. Take a look. Background is part of this week's fun, a Kleindienst extruder/moulder, heavily butchered, and drawings that are covered in dust. oil, and footprints. That's a good one.....

[TheAncientOne]

Sasha has really got me thinking about the sort of stuff I used to build as prototypes and test jigs. Most of them got thrown away when I moved house in 2002, (I made some serious errors in what I kept and what I threw or gave away, I'd become quite depressed and actually considered that my working in electronics was probably at an end).

But I did keep a some odds and ends....

The left hand pic is a text-to-speech unit based on the GI SP0256 chip set. This one is a fully loaded version with serial and parallel inputs, buffer RAM and a few other options. I need to make a cable for the PC ans see if it still works. Might be fun through a vocoder. Made with Vero 'Speedwire', (a brilliant though quite expensive prototyping system).

The right hand one is a test board for a Zilog Z* Tiny BASIC system. It's got a whole 8K of RAM The missing chip is a MAX232, I took out to use in a repair and forgot to replace. The EPROM holds the restart vector. It still works, I think, though it's a bit short on decoupling caps, because I used to use the special wire wrap 100n's, and had run out.  The big silver caps are solid tantalum electrolytics - overkill for this job, but were free from the scrap box at the time. It's done with wire wrap, a technique I still use. The tools and wire can be found quite cheaply on ebay, and you can work up a reasonable speed it you get into it.

[johnh]

The left hand pic is a text-to-speech unit based on the GI SP0256 chip set.

I remember all the neat chips GI used to make including a single chip that had four different video games on a single chip (this was 25 years ago).  My college roommate built his own 'game console' using them, as well as a home brew z-80 system.  Nice memories!

[Sasha]

Mike, nice soldering. :) How do you usually strip that wires? I`m sick just to think of doing it ...so boring.

I used to strip the thin wires with teethe for ages when I was a kid, until I get myself thinking that I better start using some tools, even stripping it with teeth was much faster. I could easily feel the length of the piece that will be stripped by touching it with the tip of my tongue. Very fast and accurate way of wire stripping, but I still wouldn`t recommend it. Ofcourse I have never cut wires with teeth :P

[Goblinz]

Mike, nice soldering. :) How do you usually strip that wires? I`m sick just to think of doing it ...so boring.

I used to strip the thin wires with teethe for ages when I was a kid, until I get myself thinking that I better start using some tools, even stripping it with teeth was much faster. I could easily feel the length of the piece that will be stripped by touching it with the tip of my tongue. Very fast and accurate way of wire stripping, but I still wouldn`t recommend it. Ofcourse I have never cut wires with teeth :P

Isn't there a condition called " electricians teeth" related to stripping too much wire... IE a notch in the front teeth? It does seem the easiest way to strip wire though.

[Sasha]

Heheh, it must be something like that. Good thing I quit on time.  :)

[nebula]

The wirewrap tool strips the wire as it wraps.  It's actually a very fast way to build stuff when size and lifespan aren't an issue.  Wirewrap connections eventually oxidize and/or loosen, so it's not perfect, but it is reliable enough to make a prototype.

[TheAncientOne]

The wirewrap tool strips the wire as it wraps.  It's actually a very fast way to build stuff when size and lifespan aren't an issue.  Wirewrap connections eventually oxidize and/or loosen, so it's not perfect, but it is reliable enough to make a prototype.

Sorry - but I have to take issue with this one. Wire wrap was originally part of an initiative by the US navy in the late 40's to try and improve electronic reliability. Two things came out of the research, crimp on terminals and wire wrap.

Wire wrap done properly stretches the plated wire around the square corners of the terminal pin, creating small cold welds. That's 24 small welds on a 6 wrap joint, (smoking joke may be inserted here). The modified wrap with the extra 3 turns of insulation around the pin is described as a vibration resistant gas-tight joint. In the days of big-iron mainframes, most backplanes were wire wrapped. Telephone companies routinely still use it in exchanges.

Do a bit of reading up - it's still a construction method of choice for certain types of high speed one-offs and very short run devices. It's on the fade now as a result of things like FPGA, but still works well.

There was a prototyping/hobbyist system that let the pin corners disrupt the insulation, and that was a bit iffy.

In normal wire-wrap you strip the wire manually. Some professional 'gun' type systems have 'cut - strip - and Wrap' bits in them but they are mind blowingly expensive (£180 for a bit and sleeve), and also require a special wire. Normal wrap wire is Kynar insulated, the one for the auto strip bits uses an insulation called 'Kapton'. If anyone can get me some I'd be very grateful - I have a 'cut strip and wrap' bit that won't work with the wire I can get, sadly.

Ther used to be amazing robot wire wrap machines that would wrap wire a backplane from a punched tape..

Basic tools are shown here, for manual wrap work.

In answer to Sasha, the wire strippers I use are pictured too. I stopped stripping wire using my teeth when a friend at school got wire jammed between his front teeth and broke one.

[stryd_one]

heh, 6 wrap joint :D

[/tilted/]

6 wraps? That's a lot of paper...

[Sasha]

Mike, thanks for an answer and pictures. I must admit I`ve never seen that tools. I know about and own just 2 types of wire strippers and I don`t like any of them.

First one is this tool. Nice one, but not good for very thin wires.

and this is the second stripper I know about. Not comfortable to work with, especially with thicker wires.

I must search for some examples of using your tools to strip and wrap the wire so nicely.

@ titled

you must be smoked a lot of 6 wrap joints.  :D

[Artesia]

old school computing, im old enough to remember the consumer application of audio tapes for program storage :)

..yes, old school computing was akin to some kind of religious ritual torture that meerly seemed to exhist for its creators amusement. Im glad certain aspects of the old days are long gone; and wish that others were still there :/ :)

as for that kind on construction, is that trying to recreate the kind of painstaking torrture involved ? ;) ..ill give a prize to the first person to sucessfully recreate a commodore 64 entirely (as much as possible) on smt ;) :)

[TheAncientOne]

as for that kind on construction, is that trying to recreate the kind of painstaking torrture involved ? ;) ..ill give a prize to the first person to sucessfully recreate a commodore 64 entirely (as much as possible) on smt ;) :)

Start giving now.... unless you mean a one-for-one replica.

http://en.wikipedia.org/wiki/C-One

http://www.c64upgra.de/c-one/

http://www.syntiac.com/fpga64.html

I've been talking to a couple of people who work on FPAA's about a possible SID clone. They said they thought it was already underway. We just need to find out where.

[stryd_one]

FPAA...SID clone

*drool*

[Artesia]

damn.. fpga peripherals; thats a much better way to impliment :)

glad to see old school computing alive on modern hardware :)

FPAA.. I didnt know such a thing exhisted yet :o ..goodness that could have some potential - {gets very interested :)}