Data General Corporation Nova 1200 Class

    The Nova 1200 and 1210 are sister machines differing chiefly in the number of slots in their backplanes; the 1200 has seven, the 1210, four. Both are what can be known as "half height" machines, in that they each occupy half the standard 10 1/2" height of a "standard" EIA rackmount module. A third model, the Nova 1220, was produced with an enlarged backplane capable of mounting 14 boards; this model was also known as the "1200 Jumbo". My collection lacks a 1220. The photograph shown here is of my Nova 1200; the 1210 is virtually identical in appearance.

    The Nova 1210 has the power supply located beneath the board cage, whereas the 1200, with its increased board capacity, locates the power supply behind the main logic area. They are capable of running either from 120 or 240 VAC, 50 or 60 Hz, jumper selectable.

    The 1200 CPU is implemented on a single 15"x15" PC board with a pair of 100 pin connectors that interface to the backplane and is located in slot 1, the bottom slot in the chassis. This board contains the ALU logic, the memory and I/O control circuitry, as well as all the timing generators. The machine uses time state logic rather than microcode. The basic cycle time is 1200 ns. The type of logic ICs used are SSI and MSI (Small Scale Integration and Medium Scale Integration) TTL (Transistor to Transistor Logic).

    Both machines utilise magnetic core memory for internal storage.

    The Nova programmer's console was standard across the the early Novas. Two rows of indicator lights display the current memory address and active data. Machine status is shown toward the right of the indicator panel. There are 16 data switches beneath the indicators, and control switches on a panel below them.

    Designed by DG to be a low cost member of the Nova line, the 1200 series utilises an ALU data path width only four bits wide (passing through a single 74181 chip). It performs its 16 bit operations by sequentially working on 4 contiguous bits (a nibble) at a time to build a complete 16 bit word. The accumulators, to the programmer, are 16 bits wide, and like other Novas there are two complete sets of them that are kept in sync with one another. Memory and I/O busses are full 16 bit paths.

    A very basic Nova system in this class might well consist of only three PC boards; the 1200 CPU, a memory board (they came in several sizes ranging from 4 kw to 32kw), and a basic I/O board. The I/O board contained logic for the console Teletype , a Centronics line printer, a real-time clock, and a paper tape reader/punch (all of these devices were options from DG; if an option was not purchased, the corresponding ICs on the board were omitted). A more advanced system could be created by adding a disk controller (requiring use of one backplane slot, thence using all four available in a 1210) and drives.

    There's a document online here which details the Nova basic instruction set .

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