On Jan 14, 14:26, Ethan Dicks wrote:
>
> --- Richard Erlacher <edick_at_idcomm.com> wrote:
> > I do believe the main reason for the 68010's appearance in what was
> > previously a number of 68000 applications was that it could support
> > virtual memory, while that was awkward on a 68K.
>
> That's my recollection as well.
There are two relevant differences. The first is that on the 68000 (and
68008), reading the system byte in the status register isn't privileged, so
MOVESR works in user mode as well as supervisor mode. In the 68010, that
was corrected and an extra opcode was added to allow reading the user byte
(condition codes) in user mode. The second difference is that the 68010
has the VBR (vector base register) so different interrupt/trap vectors can
be used in different modes; the vector base is fixed in the 68000/68008.
There's no difference in things like address range, modes, MMU
interfacing, etc. Those changes came with the 68020.
The other changes were improvement to the microcode, which made loops
faster.
--
Pete Peter Turnbull
Network Manager
University of York
Received on Mon Jan 14 2002 - 17:29:13 GMT