Data General Corporation Nova 3

    This originally was intended to be acquired as a working example, but things went awry as they will, and I wound up with a backplane, a few basic I/O boards, and the front panel. Oh, well...

    The story, however, has a happy ending. Fortunately I came into possession of a CPU card and a pair of memory boards for the machine (Thanks, BJ!); it's well on its way to full health again!

    The machine executes a superset of the standard Nova instruction set. The main additional instructions have to do with the fact that the Nova 3 has a built- in stack requiring an additional two internal registers. The stack hardware is controlled using eight I/O instructions directed at device ID 1. Device 1 also controls the hardware multiply/ divide option, which this machine lacks. A description of the basic instruction set is available here as well as one of the extended instruction set .

    The Nova 3 is implemented on a single 15 x 15 inch printed circuit board and uses many small 32 x 8 ROMs which take the place of combinational- logic function generators (the machine cannot be considered micro- coded). The ALU is a full 16 bits wide and is constructed using four 74S181 chips with full look- ahead carry propagation. A memory management and protection unit (MPU) was available which enlarged the basic machine's mainstore capacity from 32 kW to 128 kW; my example lacks the MMU/MPU option.

    There were at least two separate models of Nova 3 - the 3/4 and the 3/12 (aka 3/D). The number following the slash denotes the number of slots in the backplane. This example is a 3/12. In both of these, the CPU board resides in slot number 1 (the bottom).

    The 3's front panel style borrows heavily from the Eclipse console but uses a different colour scheme and shorter switch paddles which are thematically closer to what the "classic" Novas had. Thanks to Terry Kennedy for the temporal correction.

    Unlike the "standard" Nova console the Nova3 has but a single row of indicators (the ones on this example are incandescent). What is displayed on them depends upon the context of operation and the position of the large rotary switch to the right of the lamps.

    If you've used a standard Nova console, or an Eclipse one, the operation of this model is fairly straight- forward, though I do miss the additional row of lights. To facilitate use of the panel with its single row, however, DG made some interesting modifications concerning usage. The lamps continuously display the current memory address unless one of the operation switches is activated, in which case the panel displays the contents of the selected memory location or, in the case of registers, the register selected by the rotary switch. The lamps display register (or memory) content only whilst the switches are activated; once released, the display shows the memory address again.

    Much to my surprise, I happened across a picture of a Nova 3 on NOAA's website. It turns out that they carry at least one Nova 3 aboard their P-3 Orion "Hurricane Hunter" aircraft. Photographic evidence of this exists. The Nova is in the lower left of the rack shown in the picture.

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