Memotech RAM Pack

Sinclair User

Stephen Adams

CHEAP IS NOT NASTY IN MEMORY PACKS Stephen Adams examines the many ways of expanding the storage of the ZX-81. There are so many ZX-81 RAM packs around these days that it is worth looking at what they can offer in the way of more facilities. First, a little explanation of the ZX-81 memory map and ROM routines would help in understanding the limitations of the ZX-81. Sinclair engineers, when they designed the ZX-81, did not expect that anyone would need more than 16K of RAM. So they took some short cuts in the design which made it cheaper and easier to access the RAM and ROM. One of the them was to restrict the upper 32K of the memory map to working the screen and nothing else. The other was that the ROM, which is only 8K long, was allowed to repeat itself throughout the memory map unless the RAM was working in that area. Those decisions allowed them to decode only the top two ADDRESS lines - A14/A15 - to determine whether RAM/ROM or RAM with DISPLAY was on at any one time, the address line A15 deciding whether the display was on or not and the display being on only in the top 32K of memory and thus dividing the memory map in half. The A14 address line divided each 32K section into two quarters, the bottom half of which was ROM and the top half RAM. As they were the only decoding done inside the ZX-81 the 1K of RAM repeated itself all the way through the 16K RAM section. When the 16K RAM pack is added, however, it is switched-off by the use of the RAMCS line on the edge connector and the RAM chips in the RAM pack do all the extra decoding necessary to divide the 16K section into individual bytes. To expand the memory above 16K required some special decoding in the RAM pack so that it did not interfere with the display, which needs a repeat of the first 16K of RAM at 48K and above in the memory map. It also required that the ROM be restricted to the first 8K of the memory ma . That was done by using the ROMCS line in the same way as the RAMCS was used on the 16K RAM pack. Memotech was the first company to produce a 56K RAM pack. Most of them are now called 64K packs but you can use only 56K and that allows you to use 48K for Basic and 8K RAM where the ROM used to be, between 8K and 16K, for machine code. There are some restrictions on using the 48K as you cannot run machine code in it and you have to be careful that the display file does not cross the 32K border. Memotech now has 16K and 32K RAM packs in the same boxes as its 64K ones, which are often used by dealers as a second choice to the Sinclair 16K RAM. Memotech has a good reputation for service. The 32K pack allows you to use your 16K RAM pack as well to achieve 48K. The boxes are made from extruded aluminium and are used as a heatsink for the internal +5V regulator. RAM wobble problems should be familiar to all readers and Memotech is no exception but the company provides a Velcro strip which binds the packs to the ZX-81 and other packs. The instructions are clear and concise in a booklet accompanying each pack but they are expensive. The Sinclair 16K RAM pack has received both complaints and praise. The complaints are from users who have had to experience RAM pack wobble, which occurs when using the Sinclair keyboard. The design of the RAM pack is such that it is not connected firmly to the ZX-81 and the top of the RAM pack rests against the top of the ZX-81 case. Every time the keyboard is used that lifts the RAM pack from the table and shakes it. The edge connector eventually becomes so loose that any slight movement will disconnect it from the ZX-81, corrupting the ZX-81 memory. Several methods have been produced to stop the wobble - flexible cables so that the RAM pack can be laid flat on the table from DK'tronics and the RAM-LOK from Adapt Electronics which bolts together the ZX-81 and RAM. The best method, though, is to buy a RAM pack which has been designed to eliminate the wobble. They consist mostly of not allowing the circuit board to be connected to the casing of the RAM pack, so that the board can move up and down inside the case with the movement of the ZX-81. A reliable stiff edge connector is also required. Some, like that from Cheetah, have also been designed to wrap round the back of the ZX-81 so that there is little movement between the two casings. Some manufacturers are also using +5V.on1y RAMs so that they do not have to provide a power supply from the +9V supply which can vary depending on the equipment used. Kayde, Camel and Econotech 16K RAMs are good examples of the first type, the first two being cased. The ZX-Panda and the Cheetah are good examples of the second type. The ZX-Panda can also be used to give 32K by adding a small PCB containing 16K more RAM inside the case. The special Audio Computers RAM pack is in the category where the design has nor been so successful. The RAM pack was specially-shaped to conform with the back of the ZX-81 but it still requires sticky pads and a special plastic insert to prompt it to work. Some of the RAM packs provide a LED - a little red light - but that only provides an indication that there is power to the RAM pack and not whether it is working correctly. The best choice is obviously a non-wobble RAM pack which is inexpensive. If you can afford it and do not want to use pre-programmed ROMs or other devices, opt for a cheap 64K RAM pack. They take up just as much power as the 16K and will also work with the Sinclair printer - see the table for a list of facilities of the various RAM packs. Basicare provides a different kind of RAM; you must first buy a base module to use its RAM, called 3 Persona. It is in 16K and 64K packs for the ZX-81 up to a maximum of 512K. That is divided into banks and you will require other modules to have the banks talk to each other. The maximum memory available at one time is 32K. It is the only system which allows you to run big programs but at the moment there is very little software to run it. Yet another type of RAM pack is available and that is the battery-backed RAM - DROM, which allows the user to do things which normally would have to be run in from tape - instantly. They can provide storage for routines to side-scroll the screen in any direction, assemblers, new operating systems to replace the Sinclair ROM or even your own favourite Basic program. A multitude of DROM packs is produced by Camel Products. Two of them work on the ZX-81, the Memic 81 and the Cramic. The Memic 81 contains one or two static 2K by one-byte chips giving 2K or 4K of RAM backed-up by a battery when the power is off to preserve its memory. That occupies any position in 8K-16K area of the memory map. DROM devices allow you to write a machine code or a Basic program and transfer it into the 8K-16K area of the memory map. Machine code can be run from there, saving valuable RAM space, but Basic programs must be uploaded to the Basic area before running the program. That means that any Basic program is limited to 8K unless the Cramic is used which is 16K long. The routines for the transfers are included in the notes with every pack and consist of machine code routines which must be run by using the USR command. The Cramic is a special case as the 16K can be switched in or out by a software switch and so a Basic program can be loaded from tape into the Cramic and sealed-off from the ZX-81. Powering-off the ZX-81 then has no effect, as the RAM module has its own battery to keep it operating. The program can be restored by powering-up the ZX-81 and running a machine code program to step back in the Cramic where you ceased. That leads to my first criticism of the notes; nowhere is it mentioned that you should save the machine code program on tape, in case something goes wrong. The code required is very short but as it needs to be put into memory before using Cramic it would have been better to load it from tape. That routine could be stored in the Memic 81, of course, which is outside the Basic area and the routine loaded into the Basic area from there. The advantage of DROM over ROM is that it can be changed. The other DROM is available only in kit from from Hunter Electronics and consists of board which plugs into the back of the ZX-81 and provides 2K of battery-backed RAM, with space for three more chips. If you wish, some of them can be turned into ROM sockets to take 2K or 4K EPROMs. The RAM pack race has now become so cut-throat that a few firms which were doubtful have withdrawn. The firms remaining are giving the customers what they want, depending on price. Cheap is not necessarily nasty any more. So look for the bargains - they are there to be found. DROMS Memic 81, 4K, £34.45 Cramic, 16K, £91.95 Basicare, 2K, £39.50 Hunter, 2K, £19.95 SUPPLIERS Basicare Microsystems Ltd, [redacted]. Cambridge Microelectronics (Camel), [redacted]. Cheetah Marketing Ltd, [redacted]. JRS (Econotech), [redacted]. DK'tronics, [redacted]. Kayde, [redacted].

ZX Computing

Tim Langdell

RAM, SWEET RAM In this review, Tim Langdell from West Dulwich looks at a number of RAM packs and assesses their value for the ZX81 owner. There's no special reason for our choosing these particular add-on memories, and they differ quite a lot in their price (from £20 to about £55) and in their facilities. They are aimed at different markets to some extent, and should not be directly compared without bearing this in mind. Hopefully, though, by discussing each of their features and quirks I may be able to give you some idea of what you might be looking for in a RAM pack. The main five RAM packs being considered are all 16K byte ones, although two of them have bigger 56K byte sisters (and I will mention these too). I'll also be comparing each of them with Sinclair's own 16K RAM pack to give you some idea of how they differ. The RAMs are from Bug Byte, Taurus, Downsway, Memotech, and Plessis. First, the original Sinclair memory pack. When this first came out it was the only one you could buy for your Sinclair computer, and at that time it was a compact, reasonably-priced design. However, most people who bought one of these RAM packs noticed that it buzzed when in use and did not like being moved or used for too long. Some of the Sinclair packs overheated quickly leading to a 'crash', and some needed only to be moved a fraction for the memory to be lost and the now infamous 'white out' to occur. Some people helped these problems by taking the RAM out of its case and using Vaseline on the rear connector but these modifications seemed a bit unnecessary. By the end of last year, RAM packs had hit the market which were more reliable than Sinclair's and didn't buzz. By the beginning of this year these RAM packs were also selling for some £10 less than the Sinclair, which more realistically reflected the drop in the cost of electronic components over the last two years. Now there are at least a dozen 16K RAM packs for the ZX81 on the market, and knowing which one to chose can be difficult. A price war seems to have started over the past three months to see who can sell a 16K RAM for least. One of the earlier RAM packs to be launched was Downsway's 16K one, although it was sold through Hilderbay, Buffer Micro Shop, and JRS. Now Downsway distribute RAM packs themselves and have added a 56K RAM to their range. Their 16K RAM pack is very small and light. It comes in a black plastic box with a gold plated edge connector protruding from the bottom. It is simple to slot into the rear of the ZX81 in the same way as the Sinclair RAM. However, it is lighter than the Sinclair and has a foam strip across it which reduces wobble (and hence potential crashes) to a minimum. Unlike the Sinclair (but like all the other RAMs in this review) Downsway's RAM did not buzz when in use. In fact, my main complaint (if not only) about it was that it had no duplicate edge connector at the rear of it, which means that it must either be the only add-on at the back, or at least the last to be added on. This is true of the Sinclair RAM pack too, of course, and many others as well. The Bug Byte RAM pack is a newer addition and true to its name is one of the biggest 16K RAMs on the market. Bug Byte claim that they put it in a large black plastic box to improve its stability. But this means that it is about three times the size of the Downsway RAM and not really any less stable, and I have my doubts about their reasoning. Nonetheless, it was also a reasonably stable RAM pack which ran happily for hours. Unlike other RAMs it has a power-on light-emitting diode which lights up to tell you the RAM is switched on. I must say that I did not see much point in this feature other than to remind you whether the whole computer is on or off. Should you be curious, 90 per cent of the inside of the Bug Byte is empty space... Memotech pioneered the big memory scene for the ZX81 when they brought out their 48K RAM extension last year. Even at about £125 this sold well and paved the way for the recent 56K byte RAMs which have suddenly appeared. Clive Sinclair envisaged ZX81 users adding no more than 16K bytes of RAM to their machine and at first it was said to be impossible to add more than this. The reason for this was that the ZX81 uses the address line 15 (A15) to produce the TV display and yet a logical high on this address line is what the ZX81 needs to detect when addressing memory space above the 32K mark. For the technical buffs the solution to the dilemma lies in realising that when the M1 line is low and A15 is high, a display is being generated, but if A15 is high at other times it must be because the line holds a valid address. No one, then, was too surprised to see Memotech produce another first with a 56K byte RAM early this year, but it was quite recently that they started offering a 16K RAM pack too. The new RAMs from Memotech are beautifully designed and blend in really well with the styling of the ZX81. They come in black anodised aluminium cases shaped to the contour of the rear of the ZX81, and therefore fit like a glove. There is virtually no wobble, but chances of wobble can be further reduced by using the foam strip which Memotech supply. Unlike almost all other RAM packs, the Memotechs have a duplicate rear connector coming out the back. It is thus quite easy to add more hardware on. Like all the other 16K RAM packs (with the exception of the Taurus) the Memotech one uses 4116 industry standard RAM chips and the whole assembly has a very professional feel to it. The 4116 RAM chips are each 16K bytes by one data line, and so eight are needed for a 16K RAM. But these chips whilst popular are not best suited for the latest micros. They need not only the usual 5 volts to run them but also a - 5 Vand 12 V supply. Makers had thus been waiting for the new 64K-by-one chips to come down to a reasonable price for these only need a single 5V supply, draw very little current, and you need only eight of them for a potential 64K bytes of memory! Memotech were the first to use these new 4564 chips, soon followed by others such as Downsway. Both the Memotech and Downsway larger memory packs are almost identical to look at as their 16K counterparts. The major difference between the Memotech packs is that the so called 64K version has four switches visible in its rear which allow you to switch out the area between 8K and 16K in the memory map in 4K blocks. This is an excellent idea and I hope other manufacturers will follow this lead. The microprocessor in the ZX81 (the Z80A) can only address 64K of memory and the first 8K of this is taken up with Sinclair's ROM (ReadOnly Memory) containing the software to run the machine, provided the BASIC and so on. Therefore the very biggest add on memory can only be 56K, and it was rather misleading of Memotech to refer to it as a full 64K RAM pack. To confuse matters, many other manufacturers copied Memotech's use of the term '64K RAM pack' just in case you though the Memotech one was bigger! Both the Memotech and Downsway 56K packs can be obtained by part exchanging your 16K RAM. Memotech give you three months to return your 16K Memopak for an upgrade, whereas Downsway seem happy to consider any 16K RAM in working order in part exchange. In use the big RAM packs are identical; giving 16K or RAM for BASIC programs, the top 32K area where you can store data, arrays, etc, and the 8K space between 8K and 16K where machine code can be run, or programs or data can be stored for transference between programs (this area of memory remains intact after NEW or after loading another program). It is important to remember, though, that with one of these bigger memories you have mapped all the available memory space leaving none for other add-ens to use such as character generators, sound boards, or memory mapped I/O ports. Only the Memotech allows you to add something between 8K and 16K, but many add-ens are mapped in the 32K region and are thus not usable. The RAM pack from Taurus offers the unique facility of either being a 16K RAM or a 14K RAM with a 2K monitor on EPROM (a form of ReadOnly Memory). Unlike all the other RAMs the Taurus fits to the ZX81 with a ribbon cable and is contained inside a black plastic covered aluminium box. There is a switch on the outside of the box to switch in and out the monitor facility. Because of the use of a ribbon cable to connect this RAM pack it is free from any problems of poor contact and wobbling. If you are interested in serious programming using machine code, then you may find the Taurus monitor very useful. I found some of its capabilities almost awesome, and nearly all of them very useful. Briefly, the monitor allows you to do hexadecimal arithmetic, set/clear/or display breakpoints, copy data from one area of memory to another, do decimal to hex conversion and vice versa, fill an area of memory with a constant, move the contents of one area of memory to another, read/write a port, display the state of the registers, display the contents of DFILE DFCC VARS and ELINE, write a REM statements of any length, tabulate the contents of memory, reset the stack pointer... and more. To give an idea of its capabilities. I wrote a REM statement of 2048 dots with one command to the monitor and filled the REM with the entire 2K of memory used by the monitor with another simple command - all in a matter of seconds. The usual method of typing in 2048 characters and running a FOR/NEXT loop to load the data into memory seems ridiculously slow by comparison. The RAM pack part of the Taurus uses the less well known 2118 low power RAM chips. The RAM performed perfectly well, but I did have a reservation about the availability of the chips should anything ever go wrong. Finally, a new RAM pack has just come into the market and is manufactured by Plessis Electronics. It has been introduced at the very low price of £19.95, undercutting the cheapest other RAMs by up to £10. It comes in a black plastic box similar to Bug Byte's, but about half the size. Like the other RAM packs it has a gold plated edge connector, and does not buzz when being used. Plessis seem to have succeeded in producing a reliable 'no frills' RAM pack which works well and is at a rock bottom price (in fact one wonders how they are making a profit). I would have preferred to see Plessis use a foam strip to reduce the chance of wobble, but that being said I had no problems with programs crashing either due to wobble or overheating. In terms of value for money the Plessis must take the prize, although by the time this review appears no doubt other RAMs will have been brought down to about the £20 to £25 mark. The Bug Byte worked well but was rather large than it needed to be and at around £30 had little to recommend it over the Plessis at about £20. Sinclair have just brought the price of their RAM pack down to about £30 too, and are no doubt partly responsible for the low price trend which began around the time of the Spectrum's launch. But even reduced in price there is little to recommend the Sinclair offering either for it is still more likely to overheat than the others and makes an annoying buzzing sound. The Downsway 16K RAM is a very neat, small one and fits very firmly onto the ZX81. It is still worth considering at around £25 as a strong competitor to the Plessis, and may of course be cheaper soon. Their 56K RAM pack at about £60 (£47.50 with a 16K pack traded-in) is good value and some £20 cheaper than its Memotech rival. However, there's no denying that the Memotechs are the best-styled and best made RAM packs on the market. It's questionable whether it is appropriate to put a Rolls Royce add-on onto a Model T (any-colour-as-long-as-its-black) microcomputer. The only real advantage of the larger Memotech (apart from its looks) was its facility to switch out the 8K to 16K area in 4K blocks. The 16K version, whilst beautifully made, seems to have little which would entice me to pay twice the price of the Plessis. The Taurus RAM pack is mainly of interest because of its integral montior on EPROM. The version of it as just a 16K RAM pack at about £46 really doesn't seem competitive. As the monitor is also available as part of an 8K EPROM board (mapped between 8K and 16K) it may be better to buy it in this form, or on cassette. At a guess I would say that the 16K RAM pack prices will now level out at about the £20 to £30 mark because at the present prices of the components involved and the companies' overheads they, cannot realistically be expected to bring the prices any lower. What we may see is a still further drop in the cost of the 64K RAM chips and as a result a drop in the cost of the 56K RAMs, too. In fact these bigger RAMs may become almost as I cheap as the 16K ones! In the end it boils down to asking yourself how much memory you need (16K is a lot) and what facilities, and then choosing a RAM pack which is in your price range and which hasn't been reported to have any obvious problems. Bug Byte 16K RAM pack, £31.95. From Caps Ltd, [redacted] or from Phoenix Marketing, [redacted]. Downsway RAM pack, 16K £24.95, 56K £69.95 or £47.45 with a 16K in part exchange. Downsway Electronics Ltd., [redacted] or from Buffer Micro Shop, [redacted]. Memopak 16K £39.95, Memopak 64K £79.00 or £55 with a 16K Memopak. Memotech Ltd., [redacted]. Plessis RAM pack £19.95. Plessis Electronics, [redacted]. Sinclair 16K RAM £29.95. Sinclair Research, [redacted]. Taurus RAM pack and monitor £54.95, just 16K RAM £45.95. Taurus Computer Design, [redacted]. My thanks are due to Buffer Micro Shop who lent me the Downsway RAM packs and allowed me to refresh my memory of the Sinclair offering. RAM pack prices are falling so rapidly it is likely that some of the above prices will be out of date. You are advised to check the advertisements in this issue of ZX Computing to get the latest prices.

The RAM pack and toolkit from Taurus.

Sinclair User

Stephen Adams

PLENTY FOR USERS TO CHOOSE FROM To lead into in-depth analyses of hardware products, Stephen Adams scans the market. There has been no shortage of developments on the hardware side of the market since the introduction of the ZX-81 in March, 1981. Most were based on designs which developed on the ZX-80 and enhanced by the introduction of the ZX-81. The main differences between the ZX-80 - even with the 8K ROM - and the ZX-81 are the appearance of a static screen on the ZX-81 - slow mode - and the extension to the expansion bus - the edge connector at the back of the ROM CS line which meant that some of the Sinclair address decoding should be sorted-out externally to the ZX-81. For the first six months or so, firms were very cautious about the ZX-81, watching the market to see whether it would take off. The first product to appear was a sound board, complete with input/output port and a motherboard from Quicksilva; that was one of the first motherboards for the ZX-81 and meant that the user could have more than just the Sinclair 16K RAM pack on the back. The next announcements appeared in September, 1981 at the Personal Computer World Show - floppy discs, RS232 serial printer port, cheaper input/output ports and, for the first time, the Sinclair printer. Since then things have snowballed; ZX-81 sales have exceeded the 250,000 mark, showing that there is a great deal of feeling for the micro and the number of firms which have been set up to deal with ZX-81 equipment has more than doubled since September. The ZX Microfair in November was an event which meant that the equipment which was promised in the glossy advertisements available previously only on mail order could be seen before purchasing. Such was the enthusiasm for that type of Microfair by both the exhibitors - Sinclair alone took more than £8,000 in orders on one day - and the users that another was organised quickly for Janaury. A word of warning to users - be wary of certain manufacturers who claim that they have a product available when all they are doing is testing the market to see if anyone is interested. It is better to write and confirm on what date they will be able to supply the product to you. Computer manufacturers have the tendency to quote a date and then supply the product between six and 12 weeks after you have paid. Bigger firms are the main culprits. I have divided this review of the hardware products available for the ZX-81 into three headings - essential add-ons, keyboards, motherboards and extra RAM. They comprise input and output capabilities where some technical knowledge is assumed; enhancements which require programming skill, but either plug direct into the ZX-81 expansion bus or the ZX-81 is modified by the manufacturer. There are two leaders in the amount of RAM you can cram into the ZX-81 memory map. The Memotech 48K RAM pack has the largest continuous Basic memory; not all of it can be used for a Basic program - only the bottom 16K (16K-32K). The rest has to be used for storing data but not machine code. Audio Computing has the largest memory pack available, 128K of RAM but only 32K of it available at any time. To switch between sets of 32K, called banks of memory, a manual switch has to be thrown and the ZX-81 has to be re-set to start up the Basic system again. That is not very convenient, as it cannot yet be operated from software or the variables transferred from bank to bank. The Memotech 48K was one of the packs I have tested; it was good value at £129 plus VAT, assembled, and is very easy to use. So the arrival of Memotech's 64K pack must be welcomed, especially as it retails for only £79 including VAT. More about this newly-released product soon. There are other external RAM packs varying from an extra 3K giving a total of 4K of RAM to a full 16K of RAM cheaper than Sinclair's. Always check that the RAM pack does not prevent you connecting other equipment after it is fitted to the expansion bus. That was the case with the Sinclair RAM pack, which meant that you had to spend at least £10 to attach anything else to the ZX-81. If you are spending that money you might as well look at the expansion possibilities after you have it. The only other RAM extension possible is to change the 1K of RAM chips fitted into the basic ZX-81 for a 2K chip. That necessitates going inside the ZX-81 and perhaps some soldering. After checking inside to see if you have one chip - just change the original chip for the new one - or two - a new-28 pin IC socket needs to be fitted - change one strap on the board. Full instructions usually are given with the kits. The new memory chip will cost at least £7 and RAM packs start at £18. Various keyboards can be obtained which are basically of the same construction, consisting of 40 professional microswitches mounted on to a bare printed circuit board. That replaces the keyboard on the ZX-81. Usually some soldering has to be done. The new keyboard usually is very light to the touch and extremely responsive. Improving the time taken to enter a program by at least 50 percent. None of the original keyboard functions are lost as they are all controlled from software. There is a wide selection of input/ output ports available which can provide from 16 to 24 bits of information on a separate bus to the ZX-81 databus. Those outputs are latched; they keep the data the same while the ZX-81 does other things. They are the only way of getting information in and out of the ZX-81 to control other equipment. They can be divided into two types. memory-mapped - can be PEEKed and POKEd from a Basic program-and input/output-mapped - using special machine-code routines. Now various attachments can be used on those ports; A/D converters which take a voltage, measure it and give out a digital number for the ZX-81 to read. D/A converters which take a digital number and output a voltage corresponding to it. Light pens can be used to draw on the screen by checking the light received against the screen layout at the time. Most of those require some technical knowledge to be able to use them. Macronics disc system will act like a super-fast tape recorder using specially-written machine core routines. They will be stored in ROM and can be used to SAVE, LOAD and store random data on 5.25in. disc. The maximum is 40K per disc and the cost is expected to be £249. It also includes the only RS232 printer port available; it will accept data only one bit at a time but many printers are available for it. There are various attachments to the ZX-81 which, although not essential, can improve the facilities available to the programmer. The newest must be the speech input by William Stuart Systems and the speech output by DCP. That means that you can program the ZX-81 to accept words like LIST, RUN and the like and have it reply in a limited number of words. Another facility is to have a colour board by Haven Hardware, which is programmable in 16 colours. Programmable character generators can create high-resolution graphics, which can then be printed-out by the very good quality Sinclair printer. Each dot on the screen can be specified, so the resolution can be 512 by 256. The Sinclair printer uses an aluminium-coated paper with all the characters being shown by black dots. Even without the character board, it can print your own-designed characters but that takes a good deal of memory. Digital cassette recorders can be bought, designed specially by Monolith for the ZX-81. They are given a registered number and are highly-tuned. If you still want to use your own recorder, Abacus has a cassette switch which will prevent confusion when SAVEing or LOADing. Motherboards can be plugged easily into the expansion port to give you more sockets, so that all those devices can plug into the ZX-81 all at once. With all those products it is pleasant to see that one manufacturer, at least, is sufficiently concerned to contact other firms to agree some kind of standard. If you intend to produce something. why not speak to Nick Lambert of Quicksilva? The final enhancement is more of a service than a product. It is called the Buffer Shop and has been set up in London to cater only for the ZX machines. It is the only retail outlet for products. apart from WH Smith, supplying only the Sinclair ZX-81 and 16K RAM pack. A greater need for any user is more knowledge about what is available. It is only through co-operation of manufacturers with magazines such as Sinclair User that the user of a ZX-81 can make a valid judgement. I can only say that I have done my part and now it is up to you.