15 Aug
2006
15 Aug
'06
10:18 a.m.
From: "Jim Battle" <frustum at pacbell.net>
woodelf wrote:
Mine also gets a little under 4 years for 10^14, not 20 years.
20 years * 365 * 24 * 60 * 60 * 1/1.24us is well
over 10^14
for your typical PDP-8. :(
My calculator says 5 x 10^14. You should also derate by the fact that no program
will spend 100% of
its cycles writing to a single location.
Actually, I think the program
JMP .
does just that. IIRC, JMP doesn't have and EXEC cycle, and the next cycle
is the FETCH from the new location. Since all cycles, are RMW, the current
location would be then written during the last half of every cycle.
But, I think we can be sure that no-one wrote an operating system where that
was the idle loop, and is running it 24/7 :-).
20 years is safe.
I'd go with 12 (maybe call it 10, to be overcautious :-)). Then you can run
the more common
ISZ FOO / or KSF or whatever
JMP .-1
loop :-). The way I run mine, another 12 years of operating time is well
outside
my expected lifespan!
I think the more compelling problems with FRAM have to do with availability
and
3.3V buffering and such.
Vince