Working into retirement
Finding replacement parts is becoming more of an effort as time goes by. "When I was first acquiring hardware," says Friend. "I was more interested in the processors than the peripherals. I now realise that was a mistake, as without the peripherals all one has is a heavy box with lights that blink. So of the minicomputers about six are in quickly runnable condition; I can mix-and-match some of the peripherals with other CPUs, but that takes time and a lot of effort."
One solution to the spares problem is online forums. Some sites, like The Vintage Computer, are extensive. There's technical support for maintaining, operating and programming old kit, as well as a thriving marketplace where members can buy, sell and exchange parts and even entire systems.
As well as being collectable, Dunfield's machines earn their keep. "I also use them frequently in data-recovery operations which I do on a contract basis," he says. This is an increasingly important reason for preserving old systems. Data storage formats quickly become obsolete, so collectors are frequently the only ones able to read archives from bygone decades. Much of NASA's data telemetry archive is lost unless someone can read its ancient IBM formats.
"Sometimes the collection gets used in a laboratory manner," adds Friend. "For instance, when the United States changed its Daylight Saving Time law in 2007, a large component of my workstation collection was used to develop and test patches to allow the production machines where I work to ride the change out without problems. I've also used the collection for teaching purposes by way of 'comparative anatomy' in helping people identify computer subsystems."
High tech antiques
With the success of sites like eBay, people have woken up to the idea that most modern cultural artefacts are collectable, and that goes for computers too. Prices are rising, but which systems are particularly worth keeping?
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"That's a tough one," says Friend, "and 'most collectible' will vary from collector to collector. I know that PDP-8s are highly sought after, and command outrageous sums on places like eBay." He's right. Originally costing $18,000 in 1965, working PDP-8s now fetch between $2,000 and a cool $20,000.
Dunfield agrees: "Interest in classic computing varies all over the map, and a machine which is highly prized by one collector might not be considered worth carrying home by another," he warns.
If it's down to preference, which types of computer attract more collectors than others? "There are a large number of microcomputer collectors (non-PC micros, that is) around," says Friend, "and a few folks who collect mainframes, so it varies primarily on the tastes of the individual."
"My own main area of interest is microcomputers," adds Dunfield, "so to my mind the most collectable computers would be the ones based on the Intel 8008. These systems include the Mark-8, the Scelbi and the MIL MOD-8."
Also on Dunfield's list are the ultra-rare Kenbak (a pre-microprocessor kit dating back to 1971) and the iconic Apple-1, of which only a few hundred were ever made. It's this scarcity that drives prices up. "I have an Atari Transputer Workstation," says Dunfield. "Only 350 of these were made, and they are highly prized by some collectors."
Cash in the attic
So, when you next clear out the shed, garage, or attic, don't throw out those old computers until you've checked the prices they fetch on eBay. We found a Sinclair ZX80 in working order for £77, with eight bids against it and three days left to go – and on the US site was a working Commodore 64 home computer from 1982 with a Buy Now price of $700.