This is actually a new machine to me! It’s only taken me over 25 years to finally get one… 😉
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 two PROMs.