Hobby Computer Kit

[MskoDestny]

I've long been fascinated by the hobby computers of the late 70s and early 80s. They were really hackable and gave the owner a better understanding of how computers work. I find it unfortunate that there seems to be very little to fill that role today (the C-One being the closest example I can think of).

To that end I'm thinking of putting together a little hobby computer kit and a book/booklet/ebook explaining how the machine works and a few "experiments" for expanding the machine. I'm a bit torn as to what direction to go in with what the base hardware should include. On the one hand, starting with an ARM or ColdFire(extension of the 68K family) SoC (system on a chip) would give enough performance to do some useful tasks (basic web browsing, MP3 playback, etc.) and they tend to come with useful built-in peripherals (timers, DRAM controllers, ethernet, etc.). On the other hand, keeping that kind of logic external to the CPU would probably be useful to the learning experience, particularly if some of it was added by the user. Also, older CPUs like the original 68K and Z80 tend to be a bit easier to hack as the busses are simpler, slower, and generally have fewer signals lines.

So this poll is here to both gauge interest in such a kit and get a feel for what kind of hardware people would like for such a kit. Feel free to comment on hardware you think should be included in the basic kit (like ethernet, audio, blinkenlights, etc.). I'd also like to know if people would be interested in assembling their own kits (surface mount components would still be soldered ahead of time) or if they want the basic stuff to be ready to go out of the box.

Here are the basic choices:
ARM SoC Based
ColdFire SoC Based
68K Family (68000 or 68020/EC020)
8-Bit CPU (Z80 or 6502)
Interested, but no idea which to choose

Note: It's very unlikely that a ColdFire version would use a V4e Coldfire so it probably wouldn't provide a very good base for an Amiga clone, though I haven't looked into the differences between the different core versions.

[MskoDestny]

While Basic Stamp and PIC boards definately fall into the right price range, they tend not to interface with the rest of the world in a fasion that teaches a whole lot about how computers work. Instead of having a data and address bus they just have a handful of I/O lines.

The XGameStation is probably the closest thing to what I'm talking about in terms of purpose and intended audience, it's based around an SX microcontroller which has the same kind of I/O line interface that PICs do.

Most ARM processor dev boards I've looked at are pretty expensive though the AVR butterfly seems pretty cheap. However, it would seem the AVR doesn't have a standard address/data bus either.

An FPGA-based soft core would probably be the most cost-effective solution, though I personally don't find that nearly as satisfying as having a "real" CPU to play with.

[MskoDestny]

@InTheSand
Well this kit isn't aimed at the Amiga community in particular, though I certainly don't mind tailoring it a bit in that direction. In general, I really like the 68K family so it's likely I'd go with something of that lineage.

@Doobrey
The 683XX series chips are under consideration, but for the educational value I tend to lean towards having fewer things integrated into the CPU itself.

@Dr Righteous
68000 and 68EC020 chips are still quite cheap, cheaper than ColdFire chips in many cases. Of course you get more bang for your buck with ColdFire.

In some ways, the ColdFire 5407 is tempting. It's the only V4 ColdFire that comes in a QFP package (most of them are BGA only). Since it's a V4 ColdFire it can run CF68KLib allowing 68K code to run transparently. Some enterprising person could port AROS to a suitably expanded kit and integrate CF68KLib so that most non-hardware hitting Amiga software could run (in theory anyway). Unfortunately it's a bit on the expensive side for the purpose of this little project.