Nova
A {minicomputer}(?), introduced some time before 1978, with four 16-bit {accumulator}s, 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 mode}s and a 10-level {stack} (like the {Intel
8008}).
[Date, speed, mini?]
(1996-03-01)