< processor > A minicomputer (?) introduced by Data General in 1969, 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 addressing 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 accessed 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 (?). The Nova originally used core memory , then later 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 ).
[Speed, mini?]
(2003-10-23)