Basicare RAM 64

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].

Memory map of the ZX-81. 0K to 8K: True ROM Area 8K to 16K: ROM appears again 16K to 32K: 1K or 16K RAM 32K to 32K: 1K or 16K RAM 32K to 48K: ROM appears again 48K to 64K: RAM for display - display file The two switches shown are independent of each other and switch 2 can choose only the first four pages.

RAM Pack: Basicare 16K Anti-wobble: Yes +5V Only: No Cased: Yes Price: £26.75 RAM Pack: Basicare 64K Anti-wobble: Yes +5V Only: No Cased: Yes Price: £76.25 RAM Pack: Camel 16K Anti-wobble: Yes +5V Only: Yes Cased: Yes Price: £20.64 RAM Pack: Camel 64K Anti-wobble: Yes +5V Only: No Cased: Yes Price: £80.45 RAM Pack: Cheetah 16K Anti-wobble: Yes +5V Only: No Cased: Yes Price: £19.75 RAM Pack: Cheetah 64K Anti-wobble: Yes +5V Only: No Cased: Yes Price: £44.75 RAM Pack: Econotech 16K Anti-wobble: Yes +5V Only: No Cased: No Price: £20.95 RAM Pack: DK'Tronics 16K Anti-wobble: Yes +5V Only: No Cased: Yes Price: £22.95 RAM Pack: DK'Tronics 64K Anti-wobble: Yes +5V Only: No Cased: Yes Price: £52.95 RAM Pack: Kayde 16K Anti-wobble: Yes +5V Only: Yes Cased: Yes Price: £29.95 RAM Pack: Memotech 16K Anti-wobble: No +5V Only: No Cased: Yes Price: £29.90 RAM Pack: Memotech 32K Anti-wobble: No +5V Only: No Cased: Yes Price: £49.95 RAM Pack: Memotech 64K Anti-wobble: No +5V Only: Yes Cased: Yes Price: £79.00 RAM Pack: Sinclair 16K Anti-wobble: No +5V Only: No Cased: Yes Price: £29.95 RAM Pack: ZX-Panda Anti-wobble: Yes +5V Only: Yes Cased: Yes Price: £19.95

Sinclair User

Stephen Adams

MAXIMUM EXPANSION WITH BASICARE Stephen Adams reviews a system which gives the ZX-81 limitless flexibility. The Basicare system consists of a set of modules all housed in the same long, flat, silver, shaped boxes. The boxes are stacked vertically on top of each other, connected by a 64-way white edge connector. The edge connectors act as the spine of the system and have additional control signals to those from the back of the ZX-81. The extra control signals are used to expand the memory size beyond the 64K limit of the computer and also give it its flexibility in design. The system can be expanded at any time by plugging-in another module on to the top of the stack and the range of modules allows you to have as much RAM as you need in small or large jumps and to attach any number of printers and ports to the system. The basic module is the Persona which has to be at the bottom of the stack and is the device through which the computer communicates with the RAM and other devices. The Persona contains refresh circuitry so that the dynamic RAM does not have to rely on the REFRESH address from the computer. As the REFRESH (R) register is used for a different purpose on the ZX-81 that is a good idea. It also means that if the computer is changed to a type which did not have a refresh signal for dynamic RAM - a Vic, for instance - dynamic memory could still be used. The reason for using dynamic memory is that it reduces the number and size of the chips dramatically when compared to static RAM. The Persona also buffers all the address and data lines so that no great strain is placed on the signals from the ZX-81. The Sinclair ROM and 1K internal RAM can be turned-off if required to insert your ROM - the internal RAM on the ZX-81 has to be turned-off when using any other RAM pack anyway but that facility is provided to give the user a choice. Two pins are provided to re-set the system without pulling-out the power plug. Basicare even supplied a switch mounted across those pins on the system I was using. On a larger system each page has to be set up using the reset switch on powering-up the system, so that can be very useful. The other thing about the re-set switch is that it effects only the page of RAM on which you are at the moment and so does not erase any of the program or data in other pages. The other two pins are for selecting DATA or Toolkit sections of memory using the Minimap or changing the use of a particular RAM pack. In that case a jumper wire must be used with a plug on each end to connect between the back of the Persona and the module concerned. Basicare can supply the jumpers if required. All the modules have one or two holes in the back either for connection to other equipment - in the case of the Pericon printer module - or choice-selection pins. The selection is made usually by inserting small blue pins on to the Molex pins to join them together. All the blue pins required are supplied by Basicare when you buy the module. It is a pity that some standardisation could not have gone into the positioning of the choice pins, as every module seems to have a different set-up and the pins on the Pericon module have even been moved to the right-hand side of the case. The RAM modules for 16K and 64K have to be allocated a bank number and a page number via the choice pins. Each bank is made up of four 16K pages. On the 16K RAM modules the RAM can be put into any page of any bank so long as there is not another module allocated there. On the 64K modules the RAM must all be in the same bank because they use single 64K chips. The system is set up for four banks when using the Minimap module and only one when it is omitted. If you want more than 32K of dynamic memory on the system you have to include the Minimap in your calculations. The memory map under the Basicare system is divided into 16K sections, with some sections divided into 4K and 8K sections due to the way the ZX-81 hardware was designed. The two biggest sections, called File A and File B on the normal ZX-81 system, would be covered by the l6K RAM pack as it appears twice in the memory map. That is because the File A area is used to store the program and data and the File B area used to display the screen created in File A. On the Basicare system those two areas are switched together, even though the two RAM areas may be split to make better use of the RAM. Some provision for a TV display must be made in Page 0 so that the user can see that the system is working. In other pages the File B area may be used as a data store, but not by Basic, or as an alternative TV display. Basicare suggests that alternating between two File Bs would be a good way of providing animation. Any dynamic RAM must be located into one or both of the File areas. Under a non-Minimap system that would limit the user to a maximum of 16K, as File B would have to be a reflection of File A to see any results. The bank and page number of each module and whether it appears in File A/B or both is on without crashing the system. Using only the Persona and RAM packs, 56K of RAM can be used as the system needs a Minimap module to control the extra RAM. The Persona plugs into the ZX-81 expansion port - the large hole at the back - and the only device you can use with the Basicare system is the Sinclair printer. That is because it is an I/O-mapped device which is excluded from the Basicare system, which operates only on memory-mapped devices. I/O ports could be used but the ports must provide a PCB edge on which to connect the Basicare system and they must not draw too much power. Power must be a consideration on such a system as the ZX-81 is supplied only with a 700ma power pack, unless you have bought a printer with a larger 1.2 amp power supply. Every module you use must be supplied with power from somewhere; at the moment that is from the ZX-81 power supply via the 9V output on the edge connector and the internal +5V regulator in the Persona. Provision is made at the back for power to be provided direct into the back of the Persona but a power pack is not yet available from Basicare as a standard item. Users therefore will have to limit their systems to what the Sinclair power pack can provide - a 16K RAM and Persona on the 700ma power pack - or build their own. The connections at the back are via standard Molex plugs - 0.1in. spacing - and the system can be driven from a +12V or a full +12V/-12V/+5V supply. A car battery, for instance, could be used as a standby or main supply for the system. The other set of Molex pins on the back Of the Persona module selects the different set-ups which can be required, determined by the pins on the back Of each RAM module. Switching between RAM pages - 16 in all, from banks of four pages - is done by one POKE to a memory location inside the Minimap. The Minimap is located in the SLOT area at Slot 0 or memory location 45440. By PEEKing at that location the page number for both the File A/B and the Data/Toolkit areas can be determined. That is the main area where machine code can be stored and EPROMs and user-deftnable graphics modules can be located. It is 8K long and is over-used at the moment on the ZX-SI for every thing from speech to graphics add-ons. None of them will work with the Basicare system, as no Sinclair PCB connection is provided on any of the available modules. Putting them on the computer PCB and then plugging-in the Basicare system at the back would knock out both systems. Basicare provides two modules which can go into that area. Both are based on 6116-type static RAM chips. RAM 08 can give up to 8K of RAM and the DROM provides up to 8K of battery-backed memory - a nickel-cadmium cell inside the module charged by the computer. The DROM module can have a USERFONT option fitted which gives user-definable graphics. The RAM 08 can also contain EPROMs up to the same 8K and the DROM can have 2K sections write-proteCted so that you cannot wipe out data or machine code accidentally. With the Minimap in place and a few jumpers the Toolkit section can have four different pages using the same POKE to switch pages as the dynamic RAM. The Toolkit and Data areas are switched together and the page numbers can be different from the dynamic RAMs. Using the Toolkit or Data areas to store variables is the only way to exchange them between programs in different pages. For example, to transfer number A from the current page to page 0 would require to use a program like this: 100 LET PAGE=PEEK 45440 110 LET FILEAPAGE=INT (PAGE/16) 120 LET TOOLKITPAGE = PAGE - INT (FILEAPAGE*16) 130 REM FIND TOOLKIT PAGE NUMBER AND CURRENT FILE A PAGE NUMBER 140 POKE RAM08,A 150 REM MUST BE 0 TO 255 160 LET FILEAPAGE=0*16 170 POKE 45440,FILEAPAGE + TOOLKITPAGE The program would find from the Minimap the current Toolkit and File A (program) page numbers. The Minimap number is always made up of File A "Page" number multiplied by 16 plus the Data/Toolkit page number. Then POKE the RAM - RAM08 - in the Toolkit area with A.Strings and decimal numbers would take more than one memory location to store them, so the user must devise a system to transfer them correctly. The new POKE to be made to the Minimap must then be calculated to keep the Toolkit page the same but to alter the File A page to 0. When the POKE has been done the program in the File A section of Page 0 will then be operating, so the number must be retrieved by a LET A=PEEK RAM08 somewhere in the program. Basicare has provided no hints in the documentation on how variables should be passed between pages and has left it to the user to devise a system which will lead to non-compatible software on the same system. Apart from some printer routines, the user is left to make up his software. Each system may be individual to the user but it would have been pleasant to see some software available. The Data area can also be used to transfer variables from one page to another but cannot be used for machine code. That is because of the way the ZX-81 hardware was designed. On a non-Minimap system that can be used as part of Basic memory by POKEing two of the system variables to alter RAM-TOP. On the Minimap system, however, the program must be stopped from using that area for Basic as it would destroy the program when any switching was done. The same method as used in the Toolkit area therefore must be used to transfer variables from page to page. Using that area - 8K long - for the transfer of variables leaves the Toolkit area free for the controlling routines in EPROM or RAM. The RAMOS module can be used only in that area and requires a jumper wire to change it from its normal Toolkit area place. The use of the path area is not mentioned in the documentation but I assume that it might be something similar to the BBC computer TUBE interface which allows you to have a common memory area between various computers. The SLOT area is where all the input-output devices are located, such as printers, disc drives and ports for controlling devices outside the computer. It is divided into seven SLOTs and each has its own set of addresses with the 4K area of memory. The device types-in each SLOT which can be divided into four device types and each device type has up to 32 addresses allocated to it. The Pericon and Minimap are the only devices available for that area. The Minimap uses SLOT 0 and the Pericon SLOT 7. The Pericon modules contain 8255-type, three-port chips, one of which is used to drive a parallel Centronics-type printer. The Pericon-C module can be used to drive any printer as the software program is stored in one of the File A pages. Storing different routines in different pages allows you to use them as one long program, since when you jump to a new page all the system variables are changed, too, so you continue where you ceased when you last used the page. When you set up a program you must go through all the pages to be used and RUN the program in them, so that when you return to a page you do not have only a LIST of the program. Menus in each page would help to give you the choice of jumping to another page or using the routine in the current page. The hardware is fairly simple to use; if there are any complications with a particular module Basicare provides a program of part Basic and part machine code which will help you. That is true only of the USERFONT and the Pericon printer modules. The details on the system are of a technical nature and very sparse on how the system works inside the modules. The details are split into sections to go with each module and although there is a brief description of the system at the beginning, it is not sufficient to help the first-time, non-professional user. Programs and routines to enable you to make an easier use of the system, which is complex, are nonexistent. It would have been better if Basicare had produced a manual which described the system in its entirety than to split the information into details on the individual modules. Some software routines should be made available on tape or in EPROMs to allow the user to control the system he is trying to use. Routines such as the automatic transfer of certain variables between pages using a specified module in the Data or Toolkit areas would help. The storage of printer routines, for instance, should not occupy RAM space in the main program - File A - area. I know that restricts the use of the system but it allows users to swap software or for Basicare to provide some standard programs on tape. The minimum usable system would therefore have to consist of a Persona Minimap - because there are cheaper ways on the ZX-81 to have more memory in a 64K memory map - at least two pages of RAM and a RAMOS module in which to store data and machine code routines. All of the software would have to be run in from tape, unless you invested in a DROM module or had someone program it into a ROM. That means that the program and data would first have to be loaded into the File A area and then transferred to the Toolkit area. In that case the high-speed cassette system or disc system Basicare says it is producing would be useful, as well as some machine code routines to transfer data from one area of memory to another. Dynamic memory of 52K and up to 64K of Toolkit/Data area memory can be provided on the system - not 1MB as the advertising suggests - and this will take some organising. Any commercial software bought for use on the ZX-81 will have to be limited to 16K, unless modifications are made to it to make use of the Basicare system way of doing things. The hardware works well and so long as the power can be supplied will allow the user to extend the RAM and ports to its maximum. The connection to the ZX-81 is good and the system should not suffer from white-outs. The user can extend the system as and when he wants but is restricted at the moment to Basicare modules; none of the Sinclair equipment apart from the printer will work. The software and documentation with the system needs to be expanded to make it easier to use. Its popularity will depend on whether Basicare can produce Personas for different computers and whether it and other manufacturers produce sufficient modules for it. The cost must be compared to the need to have extra memory, as its initial cost is reasonably high.

'Apart from printer routines, the user is left to make up his software'

'The user is restricted at the moment to Basicare modules'

Memory map of the ZX-81 using Basicare. 0K to 8K: ROM Area (Not Switched) 8K to 16K: Toolkit Area (Switch 1) 8K 16K to 32K: File A Area (Switch 2) 16K 32K to 48K: Data Area (Switch 1) 8K 48K to 52K: Path Area (Not Switched) 4K 52K to 56K: Slot Area (Not Switched) 4K 56K to 64K: File Area B (Switch 2) 16K The two switches shown are independent of each other and switch 2 can choose only the first four pages.

Personal Computer News

Ian Scales

NAME: Organic Micro MANUFACTURER: BASICare Microsystems [redacted] PRICES: Persona £28.70, Minimap £34.45, RAM 08 (2K) £22.95, RAM 16 £25.25, RAM 64 £74.70, DROM (2K) £37.90, Toolkit £20.65, Pericon-a £26.40, Pericon-b £32.15, Pcricon-c £40.20. OPTIONS: Userfont £8, additional 2K for RAM 08 £6.32, additional 2K for DROM £7.48. ZX81 TOWER OF POWER The Organic Micro concept could give your ZX81 a gigabyte of memory. Ian Scale explains. Is the conventional concept of 'peripheral' outdated? Imagine a system that costs £49 to start with but grows in modules to provide megabytes of memory. It also enables you to tailor character and graphics sets, store programs in non-volatile memory, add a printer and magnetic storage and control robots or measuring equipment. These are the claims for BASICare's Organic Micro. It consists of a marriage between a Sinclair ZX81 and BASICare's range of modular memory and interface cards. BASICare's Organic Micro concept cuts across definable boundaries. It's technically a series of peripherals for a Sinclair ZX81, but it's also planned to offer a 16-bit processor that ousts the host micro - some peripheral. The idea is that you build your own system from a ZX81. You start with a couple of modules to organise the memory map and buffer the Sinclair signals. Then you just keep adding more memory and interfaces as you require them. The physical problem, of delivering such a system have been overcome by going high-rise. Instead of an untidy slum of boxes and wire, the modules interlock and are fastened with 64-way bus connectors on the bottom and top of each module. So long as your ceiling is high enough (see picture), it should be possible to keep stacking until the bank balance gives out. The Organic Micro, says BASICare, avoids the trauma of making the big leap to a new system and writing off the old one. When the system begins to show its limitations new modules are simply bought to bring it up to scratch. Eventually older, obsolete modules can be removed as new 'whizz-bang' gadgets are bought to replace them. Like its owner, the system can grow and change; continually replacing cells, but keeping its soul intact. The most immediate advantage to the ZX81 owner is mega memory - up to four megabytes. This sounds rather like towing a lorry with a mini when you consider that the ZX81 comes with 1K RAM and has a conventional address space of 64K. This means the processor is capable of dealing with only 64,000 characters of memory at one time. The BASICare system gets round this problem with a technique called paging, where the processor literally switches between 'pages' of memory. Imagine a telephone network. Telephone numbers of four or five digits can be exchanged between people in the same area. People living in another area could have the same local numbers, so when a connection is made between areas it is necessary to dial out of the local areas using an extra code of digits. The destination of the connection is then determined by a set of local digits. 'Paging' involves much the same technique (see diagram, page 53). Peter Choi, the man who developed the Organic Micro, sees a progressive increase in the viability of solid state storage to the point where it overhauls and replaces the magnetic disk. The micro of the mid to late '80s will therefore have several megabytes of memory. This will contain all the user's data files and programs, and back up could be provided by some form of tape system. The memory need never be cleared, although Mr Choi sees users initially saving memory onto tape at the end of a session and re-booting when the micro is used again. By this stage true 16- or even 32-bit microprocessors and their attendant software will have put paid to 8-bit chips, and the micro will be able to address megabytes of memory. Remember, too, that even an address space as large as one megabyte could be multiplied by page switching - so a user could conceivably have close to a gigabyte of data - not just a DOS away but literally at the fingertips. Heady stuff - but what has this to do with putting pep into a Sinclair. Pray, read on. Normally a manufacturer's visions of the rosy future must be taken with a grain of salt. Most would rather sell computers to an existing market they half understand, and leave the future for another day. The BASICare vision is actually being allowed for in the present range of products. The liftshaft of our fanciful high-rise comprises a full 64-way databus which could theoretically address data for a 32-bit processor. But in the medium term BASICare has its eye on the 8088 16-bit processor and the IBM PC operating system MS-DOS as a likely upgrade path for Organic Micro users. This is rather neat, as it resembles the breeding strategy of the cuckoo. The BASICare egg is deposited in the Sinclair nest, grows in value beyond the initial Sinclair investment then kicks the Sinclair out and takes over completely. BASICare is promising its 8088 housed in a replacement keyboard unit for the ZX81. It is also working on configuring the Spectrum and considering other makes and models. GROUND FLOOR MODULE Present configurations of the Organic Micro always start with the Persona. This 'ground floor' module links in the ZX81, and buffers its signals to perform a few organising tasks on the data flowing between the processor and the modules. The Persona gives you access to most of the features except memory over 64K. To go any higher the Minimap system must be configured. This acts as the telephone exchange for the different 64K areas of memory, and switches appropriate pages in and out to the processor when they are required by the program. RAM 08 is a low-cost memory module with 2K expandable to 8K by the inclusion of extra RAM chips. RAM 16 and RAM 64 are available for the more ambitious. TOOLKIT MODULE The DROM module is a taste of things to come, and relates to BASICare's concept of permanent memory. It uses low power CMOS static memory and 2 to 8K of development programs or routines can be held in place after power-down by a long-life nickel cadmium battery which is charged during normal operation. The 2K segments can be protected against accidental overwriting by manipulating 'shunts' with cap pins protruding from each module. EPROMs are configured into another class of module called Tool kit. The Tool kit is a conceptual receptacle for handy routines which can be called into a program. The idea is that routines are developed and tested on DROM and then committed to EPROM and left on standby for use with various programs. Userfont comes as an optional extra for purchasers of RAM 08 and DROM. Using it you can create your own characters, particularly lower-case characters, to give the otherwise rudimentary Sinclair text a bit of class. It also allows specially defined characters to be combined to create blocks of graphics for high-resolution animation of games or diagramatic displays. The Pericon modules provide a means of getting some of the results of these features to the outside world. Pericon-a is defined as a general purpose input/output tool. It provides three eight-bit ports for connection to LEDs or relays. Pericon-b also provides three eight-bit ports which consist of 24 lines of buffered output. It can be used to drive relays directly or very long signal lines. BASICare is also working on a fast-transfer cassette machine and an analog-to-digital, digital to analog converter. To make use of the Organic Micro you have to have a good grasp of programming - the modules are mostly for people who know what they are doing, or at least are prepared to sit down and start learning. BASICare suggests that a beginners' system could comprise a Persona and RAM 16, costing £46.90. From there extra modules could be added as the user becomes familiar with the system. This gradual approach would certainly be wise. Nothing is handed out on a plate. Commercial software is nil, except for those small programs currently available for the Sinclair. As these don't make use of the features you are buying it would be foolish to rely on them. The documentation is by no means comprehensive and a few listings demonstrating the animated graphics capabilities of the system at its various stages of growth would probably be appreciated. The fact that the information provided is rather terse shows that BASICare has yet to consider the potential of its products as an upgrade path for the massive crop of ZX81 users. Many of them have already outgrown their computers, and are hungrily watching for products which offer a reasonable up-grade path. But I am assured that BASICare has a mass-marketing plan in hand.

EXPANDING MEMORY ON A SLIDING SCALE This slide-rule diagram illustrates the memory management of the Organic Micro using Minimap. Since an 8-bit address space is limited to 64K the Minimap's job is to organise a larger memory so the processor (represented by the slide rule cursor) doesn't find itself faced with two blocks of data sharing some of the same addresses. This is done by dividing the entire memory of the system into three memory groups. Each horizontal group is sub-divided into segments. These each use the same set of addresses. Memory group II has a series of 32K segments containing Basic programs. Memory Group III has 16K segments of machine code or Basic routines, while segment I must always have the Sinclair ROM with its Basic interpreter plus some extra information to organise the modules. Using our slide-rule analogy you can see that different memory groups can be 'slid' so any segment in group II can team up with any segment in group III under the cursor (processor). Together with group I they then present a vertical 64K 'page' of memory to the processor. Imagine the processor processing information from a 64K page and using some of the information gleaned from the program to direct the Minimap to slide a different configuration of groups II and III under the cursor. Because several programs can be in memory on different segments, it is possible to use the output of one program from one page configuration to provide input to a program on another, multiplying the memory available for one program. This is especially useful for animated graphics programs.