On the question of whether F-RAM would be a suitable replacement for the CY62256
CMOS/battery solution: There was a longevity calculation posted that appears to have been
in error. The 1e14 cycle limit was said to be good for 30-years continuous access at a 1us
cycle rate. I calculate about 3-years. Perhaps 2us would be a more appropriate cycle rate
for the PDP-8 and that would make it 6-years.
That might be considered sufficient and I have added a section discussing the availability
of various F-RAMs to the article:
http://tronola.com/html/ram_for_pdp-8e.html#F-RAM
Unfortunately, the suitable through-hole devices are now obsolete but are still available
from Hong Kong/China.
I would appreciate any comments you might have.
By the way, in response to comments here about how the Omnibus interface compatibility
issue was handled, I have rewritten parts of that section. I hope it meets critical
approval now. I would like to say thanks for holding my feet to fire. I think it has
improved the article.
Steve Lafferty