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ComputerAnswers Column 20


COMPUTER ANSWERS AUGUST 1986



Copyright 1984-1989 Simon N Goodwin

(( SUB: Please make sure the pieces headed FAT JOYCE and GLOBAL NEWS run this issue; they both follow up questions printed in April and May; the FAT JOYCE one is specifically 'trailed' by Guy Kewney in the July PCW. Thanks. ))

Computer Answers is PCW's help column. We offer advice about all kinds of specific hardware and software problem, through the pages of the magazine. We also welcome further information in response to published queries.



VIEWDATA EN FRANCAIS

I'd like to be able to access French viewdata services using a ZX Spectrum and a modem. Is software to do this available? If not, where could I get information to write the program myself? I can program adequately in Z80 assembler.
Nicholas McKenna, Runcorn, Cheshire.

Teletel, the French Viewdata system, uses the same data-rate as Prestel - 1200/75 baud - but the format of information (as well as the language!) is different. Spectrum emulation software is not on the market, as far as I and the French phone service can discover, but you should have no trouble getting hold of the appropriate specification. Write to Phillipe Perron at Intelmatique, 98, Rue de Sevres, 75007 Paris, France. The French PTT have an office in London, at 50 Pall Mall SW1Y 5JQ; 01 839 2531. A standard French Minitel terminal should work first time, even from the UK.

BBC Micro users can obtain Teletel emulation software from Aldoda International; 01 794 0991. Their Telecom Gold address is 72:DTB10179.

In France you contact Teletel by dialing 16 from any phone. In Britain you must dial 01033 (for France) then 3613 9155 for Teletel 1, 3614 9166 for Teletel 2 or 3615 9177 for the third viewdata 'channel'. The interactive telephone directory is on 01033 3619 9111. You don't need to register before using the service, and there are plans to set up a (cheap rate) Teletel node in London. Until that arrives, you are advised to pick the time at which you phone carefully, to minimise the cost of the call Standard Prestel systems do operate on the continent, in Austria, Belgium, Italy, the Netherlands and Switzerland. You should be able to communicate with those systems using UK Prestel software, but you'll have to register as a user with the appropriate telephone company first.



COMPUTER CHESS

Are there any books which would be likely to help me undrstand chess game programming?
J.R Oaten, Ashford, Kent.

Yes! The classic book on chess programming, from which the majority of home computer chess programs derived their inspiration (and, in many cases, their code as well) is 'Sargon - a computer chess program', by Dan and Kathe Spracklen. It is published by Hayden, in 8080 and Z80 code versions. The book is nothing more or less than a complete documented listing of a fairly powerful machine code chess program. I recommend this if you can read Z80 code, or use a Z80-based micro.

You can get a good grounding in the technicalities of computer game-playing from 'Computer Gamesmanship', by David Levi. It costs £7.95, and is published by Century.

Pergamon Press publish lots of interesting books on computer chess, including a series 'Advances in Computer Chess', edited by M.R.B Clarke, the definitively-titled 'Chess Computer Book' by T.D Harding, and a cheaper, more light-hearted tome by Alex G. Bell: 'The machine plays chess?'. All of these titles should be available from proper bookshops.



GENIAL GENIES

I own a Genie II computer, and would like to know if there are any clubs for Genie owners and users.
Matts Sehlberg, Ornskoldsvik, Sweden.

The Genie II is a version of the venerable Tandy TRS-80, manufactured by EACA in Hong Kong. The Genie II runs just about all TRS-80 software, and there are lots of Geie owners among the National TRS-80 User Group.This is a non-profit making group which publishes a newsletter and holds regular lectures and meetings in the UK. Overseas members are welcome. Details are available from the secretary, Brian Pain, of 24 Oxford Street, Stony Stratford, Milton Keynes, MK11 1JU.



ORIC PRINT

I wish to buy a printer compatible with my Oric computer but two stockists have told me that there is none available. Would you please tell me whether this is correct and, if not, which dot matrix printers are suitable.
R.H Sheldon, Brentwood, Essex.

The stockists are wrong. A 4-colour plotter, the MCP-40 was the 'official' Oric printer but just about any printer with a Centronics interface (the most popular variety) will work happily with the machine. You'll need an appropriate cable, with an Amphenol plug at the printer end and an IDC connector at the Oric; you may find that a BBC Micro or Dragon lead will work. If the printer supplier can't sort you out, Tyepro Ltd (0223 322394) can make the lead up for you.



NETWORKS

The March PCW revisited the QL and persuaded me that my second computer should be a QL. As my first home computer is the Spectrum with a Tasman interface and the Epson P40 printer I was interested in the article's comments about networking between the two computers. Can you advise me on the hardware and software required?

I also have a VTX 5000 modem. Could this be used as an interface?
Eric Pendleton, Culcheth, Cheshire.

The VTX 5000 converts information from the Spectrum into RS-232 protocols internally, but the transmission-rate is very slow and it is not easy to get the information out. You're much better advised to get an Interface 1 for your Spectrum. This will give you a purpose-designed fast network port, compatible with the one on the QL.

The Sinclair network is a very fast, reliable system. It works at about 50,000 baud - much faster than a normal serial link - and only two wires are needed - you can use bell-wire or the cassette lead supplied with your Spectrum.

Some early QLs had problems receiving data from a Spectrum, leading to intermittent corruption of characters. As far as I am aware, transmission the other way has always worked properly. QLs made in the last year contain an extra chip which cures the problem.

You can check the version of a QL by looking at the serial number printed in green under the function keys. Anything from D13 onwards (D14, D15 etc) should work fine. Some machines with earlier numbers have also been upgraded to contain the new chip.

The software to handle the network is built into the QL and Interface 1. Just OPEN a channel to the network and PRINT or INPUT as required. If you're only using two machines you don't have to mess around with 'station numbers' - the defaults will work fine.

Much confusion is caused by the fact that the Spectrum and QL use different character-codes to mark the end of a line. The QL uses a line-feed, CHR$(10), whereas the Spectrum uses carriage return, CHR$(13). This is not a real problem, so long as you don't forget about it. The best approach is to add ;CHR$(10); to the end of every PRINT statement from the Spectrum to the QL, and to add ;CHR$(13); when printing the other way. The semi-colons stopthe machines from sending their own end-marker as well as the one required. Remember to close channels when you've fnished with them - this causes any residual data to be transmitted.



ATARI ST BASIC

I have been considering buying an Atari 520ST, but my local computer shop has advised against this, saying that the Basic is very poor, being full of faults, and that in particular the file-handling routines do not function properly. Because of this they were not stocking the machine.

I did wonder whether they were simply trying to get me to buy something which they did carry, but I have noticed that, although reviews of the machine have been favourable, none of them make any mention of the BASIC. Is it really so poor as to be unusable for any serious purpose?
John Randall, University of Salford.

Atari ST BASIC is certainly bug-ridden, and - I am told - was never intended for commercial release by the original author. It is certainly possible to write BASIC programs on the ST, but there are lots of faults: file- handling is shaky and double-precision variables don't seem to work at all, presumably because the interpreter was written in C and Atari have yet to build a double-precision library into their C compiler.

As far as I am aware Atari and Digital Research have no plans to fix the bugs - the BASIC was bought 'off the peg' - but Hisoft (0582 696421) are working on a compatible BASIC compiler which should clear up the problems. Several alternative BASIC interpreters have also been announced, but I've not had a chance to experiment with any of them.



MUPPETS & MODEMS

There are three fairly common file transfer or modem programs currently available to run on a range of hardware - MODEM7, XMODEM and KERMIT. Are any of these compatible with each other - in particular, can they communicate with each other through a modem?
C.W Rose, South Molton, Devon.

KERMIT is the odd one out in your list - it is intended to handle micro to mainframe links, and is incompatible with other packages (with the possible exception of MISSPIGGY!). MODEM7 and XMODEM, along with other popular packages like CP/M Modem and Christensen Modem are - broadly speaking - compatible, being based on the same code. Christensen was the original author.

PCW Networker Peter Toothill tells me that there are two mutually incompatible versions of XMODEM, called XMODEM Checksum and XMODEM CRC. The difference lies in the way that transmission errors are detected. XMODEM CRC is the new, more reliable version.



FEEDBACK:



GLOBAL AID

Ross Giddings has written in with good news for Tony Billing (PCW, May). Globe computer owners can obtain service from Forbes Amroe, of Links Crescent, Weston Super Mare, Avon (0934 416990). The 'Amroe' in the name refers to Mike Roe, an engineer who worked with the makers of the machine.



FAT JOYCE

Despite Amstrad's claims to the contrary (PCW, April) it is quite possible to install your own memory upgrade in a PCW-8256 'Joyce' word-processor. Several readers have written in to explain the process, and I can confirm that it is a fairly easy job, having upgraded a machine myself.

The extra memory increases the size of the RAM disk - drive M - from 112K to 368K. Thus you can copy a disk, on a single drive system, without having to swap the source and destination disks repeatedly. You can also fit a spelling-checker, and a substantial dictionary, onto the expanded RAM disk; this makes dictionary searches very fast, and frees all of the 'real' disk drive for your documents. The extra space is also available to 'intelligent' CP/M-plus software, which can use bank-switching to gain access to the extra RAM.

Eight 41256-15 dynamic RAM chips must be plugged into empty sockets on the Joyce's main circuit board. The chips are widely available. Happy Memories, of Newchurch, Kington, Herefordshire, charge £2.50 + VAT per chip, including postage: a total of £23 for eight.

The power and data connectors for a second disk drive are also present in a Joyce - neatly tied out of your way - so you can plug in another if you can get hold of the required 720K bare drive. This month I'll concentrate on the RAM upgrade, which offers a more noticable performance improvement at a lower cost.

You must take the machine apart in order to upgrade the memory. There are no security seals inside the machine, but your warranty will be invalidated if you have to take the machine in for service and Amstrad engineers can tell that you've been inside the machine. On most Joyces no soldering is required and the modification is easy to reverse if need be. However you shouldn't take the machine apart unless you are confident about your abilities - PCW cannot take responsibility if you run into problems.

Before you do anything else, unplug the machine and leave it to stand for an hour or so. The display circuit uses some high voltages which take a long time to be discharged. Six cross-point screws support the back of the machine: two at the top, two between the bottom of the display and the base, and two either side of the expansion connector on the back face of the machine. There's no need to remove the base.

Tip the machine forward so that the display rests upon a cushion, and undo all six screws. Lift the back vertically off the machine. The main circuit-board, which includes the 'expansion' connector, is in a slot between the disk drive and the monitor. Don't touch any of the other circuitry. Undo the catch at the bottom of one edge of the board, and slide it upwards, so that you can work on it easily.

There is a column of eight chips near the lower edge of the board, with a column of sockets alongside. The existing chips comprise the standard 256K of memory; your upgrade fits into the adjacent sockets. Chips are supplied with their legs slightly splayed, so you may need to bend them inwards slightly, by rocking them against a hard surface, before they'll plug in easily. All 16 chips MUST point in the same direction - you can tell one end of a chip from another by the presence of a small notch or dot, carved into one end of the plastic chip body. The notches should point away from the nearest edge of the board.

Once you have installed the extra memory you must indicate its presence to the machine. There are two types of PCW-8256. New models have a bank of four tiny switches near the centre of the circuit board. These are labelled A to D, and set to ON/OFF/OFF/ON respectively, on a 256K machine. To select 512K, reverse the first two switches so that the pattern is OFF/ON/OFF/ON.

The first Joyces had no switches. Instead, there are four links labelled A to D, and two unmarked links. To select 512K you must connect A to the top unmarked link, and B to the bottom unmarked link. If your machine falls into this category you may wish to add the switches, using an upgrade kit. A suitable kit is available for £49.95 from the source of these instructions - Micro-Bridge, of 75 Goodramgate (!), York YO1 2LS. If you can get your machine to York Micro-Bridge will fit the upgrade at no extra charge.

Re-assembly of the machine is straightforward. Make one final check on your work: squint across the rows of chips to make sure that all the legs are correctly plugged in. Then put the circuit board back in the slots, replace the back and screw it on tightly. The longest screws go at the top, and the shortest by the expansion connector. When you connect the power and load CP/M the screen will show that 366K is available on drive M.



ANDROMEDA FORMATTER

I Cartright has bought a second-hand Andomeda Zita computer and now finds that he has no program to format disks! I have not been able to track down the required program - can any PCW reader help?


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