The Nascom family includes not only the well-known models 1 and 2 but also a host of peripherals and software. Malcolm Bell evaluates the range.
The original Nascom 1 system has had a facelift and is still alive and looking good, although for most domestic and development purposes it has been superseded by the Nascom 2. At a price of £125 plus VAT, the Nascom 1 is very good value for money - it offers a full ASCII keyboard of excellent quality, UHF/monitor output in 16 lines by 48 character format, and serial output port for mass storage of programs and/or data via cassette or printer.
It is a single-board design based around the successful Zilog Z-80 CPU and operates at 2MHz. On board it supports the NasSys 2K monitor and 1K memory-mapped VDU RAM. An empty socket is provided for a 16-bit programmable input/output port. The system is fully expandable up to 64K memory if a buffer board is used. All manner of peripherals can be connected either to the dedicated ports or the 77-way bus.
The Nascom 2 is now the mainstay of the range and follows the practices already established by the Nascom 1. Again it is a single-board system but upgraded to use the faster 4MHz Z-80A CPU. Designed with the fullest flexibility in mind, the system can communicate with all standard input/output configurations.
A kit version is available for £225 plus VAT but is strictly for the advanced constructor. A ready-built version costs £265 plus VAT. Both versions are supplied with the 2K NasSys monitor and 8K Basic in ROM as standard, and provision is made on-board for a further 8K of static RAM or EPROM which can be located at any of the 4K address boundaries.
A socket also exists for a 128-character graphics ROM. A 16-bit programmable input/output port is supplied as standard in the on-board socket and additional ports can be added on the PI/O board. Again, the VDU is fully supported, and the cassette tape and printer interface are provided.
The display is 16 lines by 48 characters as for the Nascom 1 - this is probably the biggest factor in Nascom's lack of success in the business-machine market. The quality of the display on a standard TV set is acceptable although a slight wobble is experienced from time to time on some systems.
The 77-way bus is fully buffered and expansion is facilitated by the add-on boards. The Licon keyboard uses contactless keys for a long life and they are less easily damaged by the heavy-handed user or children.
In all, this system still represents good value for money and can be expanded into a full-size and powerful computer as your finances permit. There are, as always, a few operational problems but they are mostly confined to the software and are gradually being solved. The board and components have proved, however, to be robust and reliable.
The power board provides +12V, -12V, +5V and -5V rails. The +5V rail is rated at 3A which is more than adequate for the main board and up to four additional boards, but leaves little spare to power peripherals. As a kit, it costs £32.50 plus VAT and is simple to build. It has proved reliable although it generates a considerable amount of heat. Neither system includes the power board in its price so this is another initial expense.
The RAM expansion board has been upgraded and is now known as Series B. It can accommodate 48K of dynamic RAM running at the full 4MHz and is completely buffered. As an optional extra, the board can be equipped for page-mode operation allowing addressable memory in excess of 64K. The board can be bought with 16K memory for £80 plus VAT, and further memory added for £15 plus VAT per 16K.
The I/O board is essential if the system is to communicate to any great extent with realtime peripherals. It can accommodate up to six eight-bit ports, one serial port, and a counter/timer unit. For the £45 plus VAT you are only buying the board and the support circuitry - the main devices are extra.
Nascom does not market a system case, although the Kenilworth Case is approved. The company does, however, sell a frame manufactured for its machines by Vero and costing £25 plus VAT. It satisfies the need for a permanent housing for the boards but is rather large and not very attractive.
The Imp printer was one of the first of the small printers to reach the market and it represented excellent value. Yet since this market has changed so rapidly, the Imp is no longer to the fore.
The NasSys 1 monitor is a very powerful program supplied in a 2K ROM to be located at memory address 0H. It is now provided as standard on Nascom 1 and 2 so software for either system is now compatible. The program has been constructed to provide the necessary support for the usual input/output formats, has a very comprehensive program editing and debugging section while at the same time makes its own internal subroutines available for use by the user programs.
Since the inception of the Nascom range of systems in 1977, the fame and fortunes of the controlling company have been volatile. When launched on November 27, 1977 the Nascom 1 was hailed as years ahead of its rivals, and so it was - or at least should have been. In reality it had not been developed to its full capabilities and did not appear on the market for some time. The demand was aggressively stimulated and the 1,000 systems per year figure grew to 15,000.
The launch of the Nascom 2 system was intended to overcome the problems but a world shortage of 1K static RAM packages only frustrated the company still further. The inevitable cash flow problems worsened, and eventually the receiver was called in.
Following a long period of uncertainty, Alteck Ltd made a takeover bid which eventually fell through. Now Lucas Logic has given the Nascom range a new lease of life.
What has emerged from this turbulent history is both the success and the popularity of the systems, which have managed to maintain their sale figures throughout. Credit for this must go to the designers of the system and the main suppliers.
The eight restarts are used for reset, character input, relative call, subroutine call of internal subroutines, breakpoint, string output, character output and delay. You can also modify the main keyboard table and system defaults to make the operating system more flexible.
This monitor has been in use now for several years and has proved very successful. Again, the documentation is of an acceptable standard - the biggest advantage is the inclusion of the full assembly listing. This is both informative and instructive. A full list of monitor commands is given in table 1.
A xxxx yyyy Arithmetic in hecadecimal
B xxxx Break-point set
C xxxx yyyy zzzz Copy - move data
E xxxx Execute
G xxxx yyyy zzzz Generate - write a program to tape
including an execution address
H Half-duplex terminal
I xxxx yyyy zzzz Intelligent copy - moves data
with overlap protection
J Basic cold start
K xx Set keyboard options
L Load from paper tape
M xxxx Modify data
N Return to normal I/O
O xx yy Output data to a port
Q xx Input data from a port
R Read from a cassette
S xxx Single-step through program
displaying register values
T xxxx yyyy zzzz Tabulate data or write to
U User-specified I/O routines
V Verify data written to cassette
W xxxx yyyy Write data to a cassette
X xx External serial device control
Z Basic warm start
There are three new commands, P, D and Y for displaying the user-program registers, execution from 0D000H, and execution from 0B000H respectively. In addition, the Tabulate command has been improved to display hexadecimal and ASCII values, the External command, X, has additional options, and the input command, Read, now has the option of reading with an offset value. An additional feature gives keyboard repeat with adjustable blink rate of the cursor.
The Nascom Basic is provided as standard on the Nascom 2 in ROM and can be purchased separately in ROM or on tape for the Nascom 1. It is an 8K package and a derivative of the widely-used Microsoft Basic, but because it makes extensive use of the internal subroutines of the NasSys monitor, it is comparable with most 12K Basics. Table 2 shows the complement of Basic commands. Most worthy of note is the absence of Save and Load commands for string arrays, making file and data handling more time-consuming than normal. There are useful display-manipulation commands and graphic features - Set, Point, and Reset.
The speed of operation of the Basic when used in the Nascom 2 at 4MHz is very impressive - it is twice as fast as the Commodore Pet.
The Zeap Z-80 editor/assembler program is available in EPROM or cassette tape packages - £37 or £25 respectively. It is vital if any program is to be written directly for machine code. It contains an editor to facilitate the entry of programs in the assembler mnemonics of the Z-80 CPU and then translates that listing into machine code.
|Table 2. Nascom Basic
Cassette input/output functions
The NasDis is the complement of Zeap. It will read the object code of a program and display or print a listing showing the code, the mnemonic, labels all jump-entry points and provides a cross-reference list. Like all disassemblers, it cannot distinguish between programs and data, but this does not usually give rise to confusion. The package is supplied in three EPROMs at a cost of £37.50 plus VAT.
The Nas Debug diagnostic package is a 1K package that must be used in conjunction with NasDis. It provides many useful extra features such as the direct register access used in the NasSys 3, dual page mode and direct editing of the assembler listing as the program is stepped through. It is a useful addition at only £15 plus VAT.
Word processing is a complicated field and the operating programs are usually very large. So, when considering the Naspen word processor, its size of just 2K must be taken into account. There is no doubt that the facilities it offers are of great value when documenting software, and can be used successfully for letters. However, the commands offered correspond more closely to those found on an editor than on a word processor. pagination is catered for and page-width or page-length settings can be adjusted, although Naspen does not actually form the text into pages. It is, nevertheless, a useful and recommended program worth every penny of its £30 price.
The Kenilworth case is made from hardwood and steel and is designed for the Nascom 2. It accommodates the main system, power supply and keyboard. By adding support kits, up to five additional expansion boards can be included, which should be adequate for the needs of most users. It is reasonably pleasing in appearance although not up to professional users' standards. The TV or monitor can stand on the case's upper surface and all external connections are made at the rear. Priced at £49.50 for the basic unit and a further £7.50 for the two-board expansion, it is not cheap but does make a compact and practical unit.
The design of both systems leaves the cassette-input and the keyboard port open for all system input conditions. This can give rise to spurious characters from the tape or error entries. The £17.50 Castle Interface provides a more sophisticated tape-handling mechanism, motor control and printer/cassette switching. While not in any way essential, it provides a useful function.
Different versions of the program exist for the two monitors but the functions offered are identical. Both are priced the same at £28 for two EPROMS. Their main use is for entering and editing Basic programs, but they can be used for the main system control if the system reset address is set to its start location.
The functions provided are as follows:
|APPEND||Add other basic programs|
|AUTO LINE NUMBERING||with initial and step variables|
|DELETE||Single line or block delete|
|DUMP||Prints to the screen all user variables but not arrays|
|FIND||Finds and displays a specified string|
|HELP||Displays for modification a specified line - with compression if required|
|HEX||Hexadecimal to decimal conversion|
|INKEY||Input from keyboard|
|RINK||Input from keyboard|
|MONITOR||Passes control to NasSys|
|RENUM||with initial and step as variables|
|STEP||Single-step through a program displaying requested variables|
The Henry's Radio Basic Programmer's Aid is supplied only on tape at £15 and combines some of the features mentioned with the addition of cross-referencing. Screenplus is marketed at £40 and connects to one of the eight-bit ports to produce an enhanced VDU display with reverse-video options for characters, word or screen blocks in addition to screen blanking. For that price the user must want those facilities very badly.
The Sargon chess pack costs £35 and includes a manual, chess-graphics board with dedicated ROM and the program on cassette. The documentation for the soundbox programmable sound generator suggests that music can be programmed in Basic into this unit where it is fed to a three-sound channel, dedicated music chip. Then it is passed to the on-board power amplifier and 3in loudspeaker, or home stereo. It is good value at £39.50. The Arton speech board is for the man who wants everything. This speech board uses Digitaliser and can be connected to the Nascom for £85.
There is a wide range of non-approved products - the most notable being the Gemini 5.25in. double-sided, single-density floppy-disc unit sold by the suppliers for about £450.
Different versions of the program exist..." seem a bit disjointed but this is as per the original review.