THE STORY OF THE NASCOM ONE-TWO
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
(a) Ability to read data from Nascom 1 tapes directly into a Nascom
2. This works even with an unexpanded system.
(b) 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.
(c) 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
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.