VCF West: Adding A Front Panel To The 6502

When you think about vintage computers from the 1970s, the first thing that should spring to mind are front panels loaded up with switches, LEDs, and if you’re really lucky, a lock with a key. Across all families of CPUs from the ’70s, you’ll find front panel setups for Z80s and 8080s, but strangely not the 6502. That’s not to say blinkenlights and panel switches for 6502-based computers didn’t exist, but they were astonishingly rare.

If something hasn’t been done, that means someone has to do it. [Alexander Pierson] built The Cactus, a  6502-based computer that can be controlled entirely through toggle switches and LEDs.

If you’re wondering why something like this hasn’t been built before, you only have to look at the circuitry of the 6502 CPU. The first versions of this chip were built with an NMOS process, and these first chips included bugs, undefined behavior, and could not be run with a stopped clock signal. These problems were fixed with the next chip spin using a CMOS process (which introduced new bugs), but the CMOS version of the 6502 would retain the contents of its registers with a stopped clock signal.

The specs for the Cactus computer are what you would expect from a homebrew 6502 system. The chip is a WDC 65C02S running at 1MHz, there’s 32k of RAM and a 16k EPROM, dual 6551s give serial access at various baud rates, and there are 16 bits of parallel I/O from a 65C22 VIA. The ROM is loaded up with OSI Basic. The real trick here is the front panel, though. Sixteen toggle switches allow the front panel operator to toggle through the entire address space, and eight flip switches can set any bit in the computer. Other controls include Run, Halt, Step, Examine, and Deposit, as you would expect with any front panel computer.

It’s a fantastic piece of work which I missed seeing at VCF East so I’m really glad [Alexander] made the trip between coasts. Cactus is truly something that hasn’t been done before. Not because it’s impossible, but simply because the state of the art technology from when the 6502 was new didn’t allow it. Now we have the chips, and the only limitation is finding someone willing to put in the work.

The Interesting Fate Of Kenya’s First Computers

If you are an enthusiast for 1950s computer hardware, you are probably out of luck when it comes to owning a machine of your own. Your best chance will be to join the staff of one of the various museums that preserve and operate these machines, at which you can indulge your passion to your heart’s content. But what if we told you that there is a 1950s computer available for pick-up at any time, to whoever is prepared to go and get it and has suitable transport? You’d be making plans straight away, wouldn’t you? The computer in question is real, but there’s a snag. It’s at the bottom of the Indian Ocean, just at the start of international waters off the coast of Kenya. The story of Kenya’s early computing and how the machine met its fate is the subject of a fascinating article from a year or two ago on owaahh.com that had us riveted from start to finish.

Like large state-owned enterprises worldwide, the Kenyan railway and power monopolies were among the first commercial customers for computing. In the final years of the British Empire, those were ordered from a company in London, International Computers & Tabulators, and it was their ICT1202 that served the railway company. The article goes into detail about the history of the company’s East African operation, the problems of running a tube-based computer in an African climate without air-conditioners, and the 1202’s demise and replacement. We’ll not spill the beans here on how the computer ended up on the seabed and how its replacement ended up being spirited away to China, for that you’ll have to read it all. It’s worth saying, the author also has a personal website in which he goes into much more detail about his experience with computers in the 1950s and ’60s.

Not had enough ancient computer tech? A couple of years ago we toured the primordial electronic computer, Colossus, and also took a look at the National Museum Of Computing that houses it.

Respectfully Modifying the Amiga 500

Modifying the Amiga 500 to speed up access to RAM in a memory expansion pack is a well documented procedure, with guides on the process written in the early 1990’s when the hardware was only a few years old. But as they were written for contemporary hardware, they make no concessions for how one should be treating a vintage computer that’s now over 30 years old. In 1993, cutting traces on the Amiga 500 motherboard was just a last ditch effort to eek a few more months of service life out of an outdated desktop computer. But in 2018, it’s kind of like when that old lady tried to “restore” a fresco of Jesus in Spain; it might be done with the best of intentions, but you still screwed the thing up good and proper.

Such things don’t fly over at [Inkoo Vintage Computing]. There you can find a guide that details the impressive lengths one can go to if they want to perform the classic modification without any irreversible changes to the motherboard. To avoid the cut traces and soldered bodge wires, this version of the modification makes use of a novel adapter that breaks out the necessary connections on the 8372A chip.

The adapter is simply a homemade PCB with both male and female plastic leaded chip carrier (PLCC) connectors. The few pins on the chip that needed rerouting are exposed as solder pads on the adapter for easy wiring. There are even a couple jumpers on the adapter to turn the modifications on and off.

Not surprisingly, the trickiest part of building this adapter was sourcing the antiquated PLCC connectors. Assuming you can even find them, you are then left with the challenging task of soldering them together. Judging by the pictures on the [Inkoo Vintage Computing] page, it’s no walk in the park.

Another similar arrangement is used in the expansion bay of the Amiga, where a pin is virtually “cut” in the connector. A tiny PCB is soldered to a 3×2 header to reroute the signals, and another jumper is used to enable and disable the pin. Luckily, the long pins on the Amiga memory expansion are forgiving enough that the little board can fit in between them without breaking electrical contact.

We’re no stranger to the Amiga 500 around these parts. We’ve covered how to get the 1987-vintage machine online in the 21st century, as well as employing a Raspberry Pi to emulate the original floppy drive. You can even make your own faux-Amiga with a 3D printed case, if you suffer from a sort of existential dread when working on a computer that’s older than you are.

Next Week: Vintage Computer Festival Pacific Northwest

Next week something magical is happening. Seattle is getting a Vintage Computer Festival. It’s the Vintage Computer Festival Pacific Northwest, and it’s happening Saturday, February 10th and Sunday, February 11th at the Living Computers Museum and Labs.

As with all Vintage Computer Festivals, this is one with plenty of exhibits, speakers, and the ever-popular consignment shop. A few of the more interesting exhibits include a demonstration of the Syntauri alphaSyntauri, a synthesizer card and controller designed for the Apple II. When it was released in 1980, this was the first affordable digital synthesizer that competed against the Synclavier and Fairlight CMI. The difference? Synclaviers cost as much as a house, where the alphaSyntauri cost as much as a car. Also on deck is the dis-integrated MOnSter6502, a complete NMOS 6502 constructed out of individual, surface mount transistors. The Digi-Comp II from Evil Mad Scientist will be there, there will be BlinkenBones, and for anyone who wants to assemble their own front panel for a vintage minicomputer, [Oscar Vermeulen] will be there with the Pi-DP/8. This isn’t an event to miss.

As an aside, we’d really like to commend the Vintage Computer Federation for their incredible work in putting these shows together. The VCF West at the Computer History Museum in Mountain View is an incredible show, VCF Southeast has some amazing displays, and VCF East in New Jersey is a pretty incredible gathering going down May 18th through the 20th this year. The people working behind the scenes to make these shows happen are doing a service for all vintage computers and performing digital archeology that benefits us all.

Hackaday is proud to be a sponsor of VCF Pacific Northwest.

Another New Old Computer on an FPGA

How would you sell a computer to a potential buyer? Fast? Reliable? Great graphics and sound? In 1956, you might point out that it was somewhat smaller than a desk. After all, in those days what people thought of as computers were giant behemoths. Thanks to modern FPGAs, you can now have a replica of a 1956 computer — the LGP-30 — that is significantly smaller than a desk. The LittleGP-30 is the brainchild of [Jürgen Müller].

The original also weighed about 740 pounds, or a shade under 336 kg, so the FPGA version wins on mass, as well. The LGP-30 owed its relative svelte footprint to the fact that it only used 113 tubes and of those, only 24 tubes were in the CPU. This was possible, because, like many early computers, the CPU worked on one bit at a time. While a modern computer will add a word all at once, this computer — even the FPGA version — add each operand one bit at a time.

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MiSTer Upgrades Vintage Computer Recreations

The MiST project provides an FPGA-based platform for recreating vintage computers. We recently saw an upgraded board — MiSTer — with a similar goal but with increased capability. You can see a video of the board acting like an Apple ][ playing Pac Man, below.

The board isn’t emulating the target computer. Rather, it uses an FPGA to host a hardware implementation of the target. There are cores for Apple, Atari, Commodore, Coleco, Sega, Sinclair and many other computers. There are also many arcade game cores for games like Defender, Galaga, and Frogger.

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Vintage Computer Festival Switzerland This Weekend

This weekend marks the Vintage Computer Festival Europe – Switzerland, a two-day extravaganza of vintage hardware held in Zurich, Switzerland.

Of interest for this VCF will be an LGP-30 replica (a computer without RAM or ROM released in 1956), an IBM System/360 front panel, lots of blinkenlights, Swiss computers, and [Oscarv], creator of the very successful PiDP-8/I project on Hackaday.io, will be there with his minified PiDP-11/70. If you don’t have one of [Oscar]’s PiDP8 machines sitting on your desk yet, don’t worry — the 11/70 is the one you really want. It is beautiful.

As you would expect from a Vintage Computer Festival, all the standards will be there. The flea market is open, soldering stations are present, talks will be held, and very old and very rare hardware will be blinking. From our experience with Vintage Computer Festivals, Europe does it right. Last year’s festival in Munich was a blast, and this year’s celebration in Zurich looks like it will be as well.