Nova
<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?]
