6502.org

I've been wanting to build a 6502 computer for 20 years, having used a Sym 1 for my senior engineering project back in the dark ages (I went to college with Fred Flinstone).

I'd like to design my system from scratch, but since I'm terrible at clerical things, I defintely need to use a CAD system to create/tweak/modify the design.

Can anyone recommend a good open-source CAD program? I won't need PCB baord layouts, but I do plan on using wire wraps, so I need some way of assembling a parts list and point-to-point wire list.

Anybody have a suggestion?

TIA!

You could download the free software from ExpressPCB and just use the schematic program. Eagle has a free version, but I don't know to what extent it would fit your needs. I did all my design work in ExpressPCB.

Welcome! Coffee and donuts are on the table in the middle.

Take a look at http://en.wikipedia.org/wiki/Comparison_of_EDA_software .

See also my 6502 primer which is mostly about 6502 hardware design and construction, at http://wilsonminesco.com/6502primer/index.html . It has a page on wire-wrap too, at http://wilsonminesco.com/6502primer/WireWrap.html .

I've brought a lot of commercial products to market though, and I don't use CAD for schematics, only laying out PC boards, which have been up to 12 layers and 500 parts.

For open source PCB (or circuit) design, try KiCad and gEDA.
See http://stardot.org.uk/forums/viewtopic. ... 58&p=81254
And
http://www.kicad-pcb.org/display/KICAD/ ... ware+Suite (via http://teholabs.com/knowledge/kicad.html)
and
http://www.geda-project.org/ (via http://www.gpleda.org/)

Thanks, Guys! Garth, I had already found and read your excellent primer. Thanks!

If you want to use an existing design, Douglas Beattie Jr. published one here:

http://www.hytherion.com/beattidp/compu ... iy6502.htm

It includes a complete list of wire wrap points, so if you are slow and careful it should be a doable project.

Just a suggestion, but recently I found that buying all the WW wire, sockets, pins, boards, tools, etc.. was more troublesome, time consuming and more expensive than having a PCB made. Personally I'd not bother with WW in this day and age. I used to swear by it, but IMO it's just not worth it any more. Back then (197X-198X) it would cost many hundreds or thousands to have a custom PCB made so WW made sense. Now you can get small boards made for about $20 a piece in very small quantities (3 or 4) and even less in larger quantities. A lot of the PCB shops offer free software.

I tend to agree with Bill on this. Twenty-five years ago, the idea of doing a prototype on a PCB was usually financially out of the question, so wire-wrap ruled. Money was more valued than fabrication time, even when finding and fixing mistakes was factored in.

Not any more. At this stage of my life, my time is of more value to me than money, so I will opt for the PCB before reaching for the wire-wrap tools. Plus designing on a PCB makes tighter and potentially better-performing layouts easier to achieve. These days, about the only use that 30 gauge wire gets around here is applying hardware patches.

We have the "Cheap PCB Stories" topic at viewtopic.php?t=1913, about two years old. It may still be valuable as-is, but if there are updates, please post them.

Hell must've froze over, because I managed to find wire-wrap wire at my local Radio Shack ! Coupled with a generously-donated wire-wrap tool, all I need now is some parts, and some wire-wrap sockets that are sure to cost me an arm and a leg ...

As for CAD software, I use DipTrace... up to 500 pins for hobbyist use at no charge.