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Nova

<processor> A minicomputer(?), introduced some time before 1978, with four 16-bit accumulators, AC0 to AC3 and a 15 bit program counter. A later model also had a 15-bit stack pointer and frame pointer. AC2 and AC3 could be used for indexed addresses and AC3 was used to store the return address on a subroutine call. Apart from the small register set, the NOVA was an ordinary CPU design.

Memory could be access indirectly through addresses stored in other memory locations. If locations 0 to 3 were used for this purpose, they were auto-incremented after being used. If locations 4 to 7 were used, they were auto-decremented. Memory could be addressed in 16-bit words up to a maximum of 32K words (64K bytes). The instruction cycle time was 500 nanoseconds(?) cycle time for each. The Nova originally used core memory though later on they gained dynamic RAM.

Like the PDP-8, the Data General Nova was also copied, not just in one, but two implementations - the Data General MN601 and Fairchild 9440. Luckily, the NOVA was a more mature design than the PDP-8.

Another CPU, the PACE, was based on the NOVA design, but featured 16-bit addresses (instead of the Nova's 15), more addressing modes and a 10-level stack (like the Intel 8008).

[Date, speed, mini?]

(1996-03-01)


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