Nascom-2

This is actually a new machine to me! It’s only taken me over 25 years to finally get one…  And then it’s like buses – 3 come along together (more or less).  😉

The NASCOM-2 has quite a lot of enhancements over the NASCOM-1:

• Faster processor
• Greater RAM/EPROM capacity on board
• Built-in processor buffering to drive the Nas-bus directly
• 8k Microsoft BASIC on board
• Switchable start address on power-up/reset
• Keyboard extended to include cursor + graphic keys
• Improved NAS-SYS 1 monitor (in a single 2k ROM)
• 300/1200 baud Kansas City tape interface
• All graphic characters available from keyboard

The major advantage was that this computer could be equipped with enough on-board RAM to use it as a fully self-contained computer without the need for a bus system. The switchable start address allowed the system to boot up into BASIC if required, almost identically to the Tandy Level II computer. This made for a much more popular machine – especially when pre-assembled boards were offered for sale.

Almost all the extra bits that were necessary for a NASCOM-1 system were already present here. However, it is notable that NASCOM still required the user to wire a suitable relay (and driver transistor if necessary) to control the cassette deck. As almost all these systems used such a circuit it seems a strange omission.

The big increase in capability on the same PCB size (8in x 12in) was achieved in two ways. First, the workspace and video RAM was fitted as two 1k x 8 static RAM ICs instead of 16 1k X 1 devices. Secondly, much of the I/O and address decoding was achieved by replacing TTL logic with four PROMs.

 

 

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