17 Jan
1999
17 Jan
'99
12:23 p.m.
Tony wrote:
I doubt if any semiconductor memory, even
mask-programmed ROMs, will last
100 years.
Masked ROMs, particularly older (lower-density) ones, might have a reasonable
chance. Most, but not all, of the electromigration occurs when the part is
under bias.
Note that the old nichrome fusible-link PROMs suffer from regrowth. I'm
not sure whether the slightly newer titanium-tungsten PROMs have this problem
as bad. A friend has reconstructed PROM contents by optical inspection. The
regrowth is visually distinctive from original unblown fuses. I speculate
that data might also be recoverable by programming the part; regrown fuses
shouldn't take as much current to blow as unblown fuses.
There are reliable electronic stores. Braided wire ROM
is one of them.
But none of them are high-density, or are anything like the typical
memories of 1999.
I wonder how well the HP 9100 calculator will hold up? It uses wire braid
ROM for its microinstruction decoder, and PCB memory for its control store.
How long will a CRT hold a usable vacuum?