Scor­pio News

well as constructed but memory-less boards are available from a number of American firms and can be paid for with Visa or Mastercharge (Access) at extraordinarily good prices, even allowing for the imposition of VAT and, probably customs duty as well when they arrive in the UK. Service is generally quick and courteous – if you pay by credit card, delivery is very rapid (I had my board about 10 days after sending the order). If you pay by cheque, do get a quotation first, to include shipping and other charges – Lloyds Bank offer a convenient means of payment via an American Express draft which is a lot cheaper than many other methods of payment.

I must admit to being bitten by the ‘construct-a-clone’ bug. A browse through ‘Byte’ shows that JDR Microelectronics do a ready-built Turbo XT-clone main board for under $100 (supply your own RAM but it runs at 8 MHz); another firm advertises a 10MHz AT clone main board for well under $300.... Hmm. I wonder if anyone wants an XT clone with 80286 Accelerator board, SMPS etc. (yes, this is an advertisement – if Dr Dark can slip one in, I will as well!)

For the would-be clone-constructor, a major problem is the cost of memory chips. Prices have risen dramatically in recent months as a result of pressure on Far-Eastern manufacturers who have been dumping their excess chips on the Americans. The minimum memory required for most MSDOS programs is 256k (parity-checked with 36 150 nS 4164s or 9 150 nS 41256s), although 512k is more useful. Greenweld seem to obtain (from time to time) supplies of boards with one or other of these types of DRAM (usually) soldered in and removal by conventional means is straightforward but inclined to be tedious. The fact that most suppliers now sell only the assembled main boards does mean that the type of problems which Ian sorted out for me should not occur. If you are interested, it might be an intriguing and instructive route into MSDOS.

You will, of course, need floppy disk controller and video cards, and an appropriate XT or AT compatible keyboard – and at least one 40 track 5.25″ drive. It may be possible for you to fiddle with a standard monitor so that it can cope with the 18 KHz or so timebase required by the IBM video card – but suitable switch mode power supplies are available from a number of suppliers for about £25. Digitask are a useful firm for IBM PC-compatible items, but a bit of browsing through electronic magazines will provide you with plenty of addresses for other items. In particular, Matmos (in Cuckfield) or their close associate Computer Appreciation (in Canterbury) are worth contacting – they seem to obtain some remarkably good bargains from time to time – particularly for stripping down, although they seem to specialise in ‘end of run’ or lesser-known second-hand systems. I would be very interested to hear how other constructors have fared..... ●