17 Mar
2015
17 Mar
'15
1:13 p.m.
On 2015-03-17 20:03, Christian Gauger-Cosgrove wrote:
On 16 March 2015 at 23:42, Eric Smith <spacewar at
gmail.com> wrote:
You can't improve on the speed of the PIP70/HC70 combo. At that point,
the speed is just the clock speed of the CPU. It no longer waits on
memory, as far as I know.
But getting to that point would be a nice improvement already.
Johnny
Not including parity or ECC, it takes two devices
to fill the entire
4MB address space of the PDP-11/70. Either parity or ECC will require
another one additional device, which won't be fully utilized.
Ordinary SRAM is cheaper, but $110.16 for enough RAM chips to max out
a PDP-11/70 doesn't seem all that expensive, unless you're comparing
to DDR SDRAM DIMMs for PCs.
True, SRAM would be cheaper, and you can find faster
SRAM and DRAM
than the currently available MRAM (if I recall correctly). But then
you lose the benefits of MRAM in the first place: It's non-volatile,
like core memory, and doesn't need battery backup (as you'd need if
you wanted to make SRAM "non-volatile"). Plus since they're modern
devices, they would be a massive upgrade to the PDP-11/70s performance
in place of its normal MOS memory or core memory. (Whether it would be
an improvement on the speed of the PEP70, I do not know.)