Computing Dictionary
Nova definition
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)