February/March 1980, Issue 6

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Or Why Two Computers are Better than One

by Richard Beal

Is the Nascom One-Two a marvellous product of the distant future ? No, it is already here, and consists of a Nascom 1 connected to a Nascom 2 to form a new and versatile computer system with the following features:

  1. Ability to read data from Nascom 1 tapes directly into a Nascom 2. This works even with an unexpanded system.
  2. Intelligent giant print buffer for serial printers such as the Nascom Imp or Teletype. This enables output from ZEAP, BASIC or NASPEN to be routed to the Nascom 1 memory virtually without delay, and with automatic compression of blanks, to save valuable RAM space. Printing is completely independent of the Nascom 2, and can proceed at the same time as more data is being sent across at high speed. If the print buffer becomes full, the Nascom 2 will automatically wait until printing starts, or if required the print buffer can be cleared if the output is not, after all, needed. Printing can be paused at any time, and the Nascom 1 display shows the number of characters waiting to be printed.
  3. Almost instantaneous transfer of the whole of the contents of memory from one machine to the other, allowing very fast recovery of programs and data when testing machine code programs. For example ZEAP could be used on the Nascom 2, and the source code and generated machine code both held in memory. Then before testing the program, which could well crash and change the contents of any part of the memory, the whole memory is copied in a few seconds to the Nascom 1. When the Nascom 2 crashes, it is simply reset, and the data brought back. Within seconds the ZEAP source can be edited and re-assembled and the process repeated.

These facilities are very useful, and mean that if you have bought a Nascom 2, your Nascom 1 can continue to be used instead of putting it in the attic, or trying to sell it, which is rather sad after all the effort needed to build it. It also gives you another reason for buying a Nascom 2 if you already have a Nascom 1 !

At this point you may be wondering what sort of equipment you need for all this. If you have a Nascom 1 and Nascom 2, all you need is ...... NOTHING!!!

Obviously if the Nascom 1 is not expanded, only feature (a) is possible. The only hardware work required is to connect various lines from the Nascom 2 26 way ribbon cable to the Nascom 1 PIO sockets. Only one port on each machine is used, with all data transfer being interrupt driven using the handshake lines. To understand this, read the PIO technical manual until you are sure you know it all. (I have read it about 30 times and am still not completely confident). Alternatively, read on.

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