Science, Art, and Nostalgia Combined: Hands-On with the RC2014 Mini II Picasso

The venerable Zilog Z80 processor may have been discontinued, but that doesn't mean there aren't people out there still designing around it. Spencer Owen's RC2014 family of modular, expandable microcomputers — built primarily around period-appropriate technology for a home computer system of the 1980s — is the perfect example of this, and there's a new one out today: the RC2014 Mini II Picasso.

A single-board computer, though easily and impressively expandable, built around a genuine Zilog Z80 and 32kB of RAM, the RC2014 Mini II Picasso is a limited-edition artistic twist on the RC20140 Mini II with an unusual layout and an entirely unique color scheme. Sold as a kit of through-hole parts, the RC2014 Mini II Picasso is a real blend of art and science — and also a fully-functional microcomputer you can program in BASIC, Forth, and assembler, or even expand to run the CP/M operating system and a wide variety of applications new and old.

Let's warm up the iron and get building.

Hardware

• CPU: Zilog Z80 at 7.3728MHz
• RAM: 32kB
• ROM: 128kB, 8/16kB pageable
• Languages: Microsoft BASIC, CamelForth
• Monitor: Small Computer Monitor (SCM)
• Serial: Six-pin FTDI compatible, 115,200bps
• Expansion: 1× RC2014 Enhanced/Standard Bus header, keyboard header
• Box contents: Unpopulated RC2014 Mini II Picasso board, all required components, USB to DC jack power lead, colored jumpers, perspex case and mounting hardware
• Price: £101.01 (around $130)

The RC2014 family of microcomputer kits was born in 2014, when Spencer Owen decided to enter the 2014 Retro Challenge with a device that would make his name appear on LED matrices. Except the device had to run Z80 assembler, on a real Z80, built using largely period-appropriate parts. "Oh, and I'm not a programmer," he told the event organizers at the time, "and have never done any Z80 assembly stuff. Doesn't that sound like fun?"

Owen must have enjoyed it, certainly, as the project gave birth to the RC2014, a modular microcomputer based on a design released by Grant Searle. In the years since the original challenge, the RC2014 family has grown to encompass a range of board designs — with, at one point, Owen setting himself the challenge to design and build one new module a month for a whole year — and single-board spin-offs, including the RC2014 Mini and its successor the RC2014 Mini II.

The RC2014 Mini II Picasso is, functionally, an RC2014 Mini II. It has the same expansion headers, it has the same power options, it features the same processor, it runs the same ROM. You could take every chip off an RC2014 Mini II and put it in the RC2014 Mini II Picasso and it would work just fine. This is to say: this is not a fundamentally new product, for whatever "new" means when you're talking about microcomputer technology grounded in the 1980s.

What the RC2014 Mini II Picasso is, is a work of art. Owen doesn't invoke the famous artist's name in vain: the underlying PCB has been completely redesigned in homage to cubism. Nothing lines up. The sockets for the major chips are arranged higgledy-piggledy. The board edges are cut at an angle, reflected in the bundled acrylic casing — transparent, naturally, for why would you want to cover art?

The art of circuit design

The redesign goes far deeper than just moving component footprints at random and laboriously routing their traces, though. A look at the documentation supplied with the kit — designed as a supplement to the usual RC2014 Mini II assembly instructions — reveals some very interesting design decisions indeed.

The first of these is the "sunken chip," a 74HCT32 quad two-input OR gate located at the bottom of the board. This is the only chip that does not have a turned-pin socket, and the instructions detail why: while it's a dual in-line package designed for through-hole installation, the builder is told to flatten out its legs and snip off all but the thickest parts before surface-mounting it onto pads on the board's underbelly. Once complete, the chip peers up through a hole in the board — not only lower than every other component, but lower than the board surface itself.

If that sounds like an unusual approach, there's more to come. Two areas of the board are marked out for "resistor staircases" — not "resistor ladders," which are a different thing entirely, but a semi-spiral stepped staircase made from through-hole resistors. Each resistor in the five-step staircases shares a common hole at one end, fanning out as they're soldered to form the functional yet aesthetic staircase. While clearly inspired by some of the space-saving approaches of early microcomputer electronics — in particular a tendency to bend the legs of resistors so they sit vertically lengthwise to reduce their board footprint — it's something truly unique, and a sign of the effort Owen has put into the kit's design.

There is a cost involved, naturally. The RC2014 Mini II is not a challenging kit to build: with all through-hole components and a sensible board layout, it's entirely suitable for newcomers to soldering — albeit with the caveat that there's quite a lot of soldering to do, so it may be worth spreading the work over a couple of sessions to avoid fatigue-driven mistakes. The Picasso variant, though, is more of a challenge; nothing too severe, by any means, but getting the resistor staircases lined up properly — and making sure the leg of the upper-most left-hand-staircase resistor doesn't short out a pin on the dangerously-close ROM chip — does take a steady hand.

There's one more aspect to the kit that highlights Owen's attention to detail: each one is absolutely unique. Sure, the board layout is the same between all kits, and the components are the same, and the software is the same — but the color scheme is unique. When packing the kits, Owen has ensured that every one has a unique combination of colors for the board, power jack, and headers. No two will be the same.

A software smorgasboard

So once you've built the RC2014 Mini II Picasso, what can you do with it? Well, you can look at it and admire your work, for a start; Owen has even cut out a screw mount in the rear of the bundled acrylic case for wall-mounting, if you'd like to hang it in a gallery somewhere.

But the Picasso is, like the RC2014 Mini II on which it's built and all the other models in the RC2014 family, a functional microcomputer. More than that, it's the sort of thing you would have loved to have on your desk in the early 1980s: that well-regarded Zilog Z80, a generous 32kB of RAM, and — the real stand-out feature — your choice of operating environments.

The period-appropriate EEPROM included in the kit is pre-loaded with the latest RC2014 ROM image, and what an image it is. By default the system boots into a port of Microsoft BASIC written by Phillip Stevens. Pop one of the bundled — multicolored, naturally — jumpers onto the ROM selection pins, and you can instead boot into a version ported by Phil Green and featuring an integrated monitor. Two jumpers in the right place gets you Grant Searle's version, on which Stevens and Green built and expanded, itself derived from the NASCOM 2 microcomputer.

But the RC2014 machines aren't limited to just various flavours of Microsoft BASIC. Move the jumpers to the middle of the header and you'll switch to Steven Cousin's Small Computer Monitor (SCM), with two other variants available at other positions. This is provides a monitor for low-level access to the RC2014's hardware including monitoring and modifying memory, direct access to ports, single-stepping, and the ability to assemble and disassemble Z80 machine code. You can even load Intel-format hex files — a handy way of trying out a new language or piece of software without having to burn a new ROM.

That's already an impressive list, but there's more. For those who cut their programming teeth on a Jupiter Ace or similar, there's a port of CamelForth available on yet another jumper position — based on James Bowman's port of Brad Rodriguez' original, with a few extra Words and support for Intel hex files. Finally, there's CP/M.

Room to grow

At least, there's the potential for CP/M. Developed by Gary Kildall and first released in 1974, CP/M isn't a programming language but a fully-fledged operating system — and one which will be familiar to anyone who has used Microsoft's MS-DOS or similar, having "inspired" the Seattle Computer Product's QDOS on which MS-DOS was based. The ROM part of an RC2014 port is there on the chip, ready to use — but an unexpanded RC2014 Mini II can't run it, and neither can the Picasso.

To get access to CP/M, you need a second board: the RC2014 Mini II CP/M Upgrade Kit. This connects to the expansion header on the top of the main board and doubles the RAM to 64kB while adding a Compact Flash socket to hold the rest of the operating system. Once assembled — the surface-mount Compact Flash socket is pre-soldered, but you'll have to do the through-hole components yourself — you're left with a fully-functional 64kB CP/M 2.2 machine with your choice of 64MB or 128MB of storage.

The upgrade kit is fully compatible with the RC2014 Mini II Picasso, as Owen didn't mess with the positioning of the expansion and keyboard headers — though it's a very sedate rounded-rectangle shape with neatly-ordered components laid out to a precise grid. When fitted, it hides most of the Picasso's board — and everything that makes it special. If you really need CP/M that's a sacrifice worth making, but if you're buying the Picasso kit for its artistic merit you may be better off picking up a standard RC2014 Mini II at the same time to serve as a CP/M host.

You're not restricted to using the "Enhanced Bus" expansion header for a CP/M kit, of course. The supplied headers are 0.1"-spaced female, easily used to wire the RC2014 Mini II up to a breadboard for a little experimentation. You can also slot in any single RC2014 Enhanced or Standard Bus expansion board, adding features ranging from LCD screens and VGA video outputs to emulated MOS SID or Yamaha YM2149 soundcards — and if you want more than one at once, you can connect the whole board to an RC2014-compatible backplane and start slotting in multiple expansion boards to create your dream machine.

Conclusion

If you're looking for a truly unique soldering kit, get the RC2014 Mini II Picasso. Even if you have absolutely no interest in 1980s eight-bit personal computing technology, don't fancy writing programs in BASIC or Forth, and don't care to fiddle around with Z80 assembly, get the RC2014 Mini II Picasso. Its design is a labor of love, its appearance a true blend of science and art, and with Owen making only a limited number and tracking the color of each component that goes in the box you are guaranteed to build something nobody else in the world has.

But who shouldn't get the RC2014 Mini II Picasso? Well, if it's your first introduction to soldering it may prove a little frustrating at times. Pretty much every single solder joint has to be perfect, and just one or two bad joints anywhere except an unused expansion header will be enough to throw the whole system out of whack — again, something that may prove frustrating to those new to soldering.

Those who prize function over form, meanwhile, should probably pick up the standard RC2014 Mini II. It's functionally identical, has all the same ports and features, and a layout that doesn't resemble an earthquake in a 1980s Cambridge workshop. Power users, finally, would likely be better-served by the traditional multi-board RC2014 kits — though the RC2014 Mini II Picasso is fully compatible with the same backplane boards, providing a path for future expansion if you decide you'd like your system to grow.

The RC2014 Mini II Picasso is now available to order from Z80 Kits at £101.01 (around $130), including USB to barrel-jack power cable and acrylic case; an FTDI-compatible USB CDC serial adapter of Owen's own design is available for an additional £4 (around $5.20).

Numbers are, however, strictly limited, and once sold out the RC2014 Mini II Picasso will never be made again — entering the halls of history alongside previous limited-run designs including 2020's RC2014 Mini After Dark, the RC2014 Classic II and RC2014 Zed Ukrainian Specials, and the RC2014 Pro Pride and RC2014 Zed Pro Pride.