USP-CENT

Personal Computer News

John Lettice

SPECTRUM CALLS CARDS John Lettice on the trail of the Spectrum expansion route, helped by his soldering iron. How many Spectrum owners are there in the UK? The number is impossible to judge with any degree of accuracy simply because the number is growing so fast - whatever figure you come up with, it's going to be out of date within months, if not weeks. Put this together with another salient feature of the machine, the lack of built in interfaces, and you can see that there's a tremendous market for add-ons, and for devices that will let the Spectrum talk to add-ons. Of the expansion routes available, U-Microcomputers has followed a traditional one. The company has been active in the area of add-on cards for the Apple for some time now, and has recently transferred its attentions to the Spectrum. The Apple and the Spectrum need a lot of adding to before you can perform complex tasks. When you open up a basic Apple II, you'll see seven empty expansion slots. However, you don't have to bother opening up a Spectrum - it's quite clear there is no space inside for expansion slots. So the first step for U-Microcomputers was to remedy this. The company did this by producing three products. The first is the spectacularly overnamed and shockingly overpriced USP-ADAP. This is actually a simple plug device that fits onto the Spectrum edge connector and houses the mirror-image edge connector of the first backplane, which has three expansion slots plus an edge connector extension. USP-ADAP Is an adaptor costing £6.90. The only way to justify it is as an initial one-off investment, it is, however, necessary if you're to use the system. You can slot single cards into it, or you can plug them into the backplane, which then plugs into the adaptor. You can then add a four-slot extension into your original three-slotter, giving you the same as the Apple's seven. PRESENTATION Each of the add-on cards comes in its own box, wrapped in metal foil and sandwiched between two large pieces of foam. There is also a tape of driver and demonstration software included, but even so the Centronics kit, which consists of a tape, small piece of cable and two chips, looks pretty bizarre nestling in a 7.25 x 10.5in box. A brief manual is provided with each unit. The technical information tends to be short on explanation for novices. Someone has obviously mentioned this to the company, because the general purpose parallel card manual's appendix includes a short glossary which defines a printer as a 'device for producing a permanent record of data or programs in readable form.' U-Microcomputers really has got to get together manuals which start from the point of why you want it, what you can do with it, then how you do it. CONSTRUCTION The U-Microcomputers range of cards is neatly constructed. The edge connectors are gold plated, which makes for more reliable connections, but they are a bit pricey by Spectrum standards. USP-BBP3, the three slot buffered backplane, costs £35.65, while the dual channel serial interface is £34.50, and the general purpose parallel is £29.90. They're generally classy pieces of work, with a lot more potential than the conventional interfacing devices you can get, but the danger is that all that power will be locked up in the manuals to all but a few initiates. On top of this, the assembled structure is a particularly awkward shape. A full seven extra slots means you've got a structure 16in long, just slightly wider than the edge connector, protruding from the back of the Spectrum. The cards themselves bring it up to about 6.75in high. This is logical up to a point, as you could position the Spectrum so that the edifice ran up the right hand side of the TV. But it would be much better to have a system that could be put into a case of sorts, preferably with the whole structure flipped on its side and running along the back of the machine. U-Microcomputers hasn't exactly made this easy, not just because of the overall dimensions, but also because the company has been particularly generous with the overall dimensions of the cards, perhaps to avoid overheating. IN USE Starting at the beginning, you'd use the adaptor to plug in the BBP3 buffered backplane. This provides buffering for the address, data and control lines from the Spectrum's edge connector, together with card slot address decoding for seven cards, and an extra edge connector. This particular edge connector is billed as being for a ZX Printer and/or Microdrives. The latter provokes thoughts of the whole shooting match tilted over to one side, jacked up by the wedge-shaped Interface 1. I decided not to bother with Microdrives to start with. The next step is to get the thing powered up. The manual warns you against using the Spectrum's own power, and the backplane has its own socket for a power supply. If you can get the right supply for this, you can discard your Spectrum's PSU. You need to buy a USP-PSU, however, and the company hasn't finished building it yet. If you are electronically inclined you can build your own, but the sort of outputs you'll need are difficult to find. The manual gives you information on how you can link in your own PSU, but the lack of a USP-PSU is a crippling disability for the whole system. As we've said, you can run the cards individually until the power supply turns up. There's no particular difficulty with this, as there are only three more cards at present, although another five are under design. The USP-232D is particularly interesting, it's a two channel serial interface used to connect the Spectrum to printers, modems and the like. The A channel provides modem control with split speed working, while the B channel operates as a printer port, with baud rates selectable between 75 and 9600. The manual here is the most comprehensive of those supplied with the cards, and is helpful in explaining concepts like handshaking. This card needs an extra power supply if you're running it direct off the Spectrum, but this can be supplied by a PP9 battery connected to the specified terminals. Baud rates are set up by placing jumpers across one of the sockets. There is quite a lot of technical information on the Z80 DART integrated circuit, which is the heart of this particular card, so with the necessary experience you should be able to go considerably beyond LLIST and LPRINT. The USP-I/O is a general purpose two port parallel I/O board which, in addition to acting as a printer interface, gives you the technology to hook up more esoteric things such as music synthesisers. Again there is a wealth of technical detail, this time on the Z80 P10. It can be converted to Centronics with the aid of the USP-CENT kit. VERDICT Despite it's rather odd appearance, this is a system that will allow you to do a lot with the Spectrum. It'll be a hard uphill grind if you want to do much more than run a printer, but it can be done, and if you can handle a soldering iron, it'll be that much easier. I'm not convinced that the cards for the Spectrum can compete with those available for the Apple. Some of the software supplied is very good indeed, particularly the demonstration of the chip counting its way through binary. A logically presented learn as you go manual would improve matters, but until that happens, it's definitely a system for someone with specialist knowledge. USP-ADAP adaptor - £6.90 USP-BBP33 slot backplane - £35.65 USP-BPE44 slot backplane extension - £25.30 USP-PROT prototyping card - £13.60 USP-232D two channel serial interface - £34.50 USP-IO General purpose parallel card - £29.90 USP-CENT Centronics printer kit - £3.45 Contact U-Microcomputers, [redacted].

Close-up view of the system. The power supply, when ready, fits in the sockets at the bottom left.

The U-Microcomputers system hides its light under a bushel in several respects, one of the more obvious being the way very little is made of the driver and demonstration software. Mostly, you get a tape with not one but a number of programs on it, and while they do their task effectively and efficiently, some of them also give very polished demonstrations. There's also lots of scope for rewriting the literature to a 'use and learn' format, which would encourage novices to get more involved in aspects of hardware design.

The assembled system backplanes into the middle distance, and owners of U-Microcomputers' expansion boards for the Spectrum may, in a few short years, be recognised by the way their heads tilt permanently to the left from typing and looking at the screen at the same time. The whole set-up is gloriously cluttered, and the technical whizz will revel in the detailed information and diagrams in the manuals. Even the novice should find enough there to get something going.