> > Mask ROMs do go bad - a non-trivial percentage of bad dumps in MAME are masks. > > They can go bad (under extreme circumstances), but something tells me that an even > less trivial percentage of that non trivial percentage are caused by pins issues
No, chips actually do go bad even if they don't rely on trapped charge. Oxide layers in any kind of MOS will eventually degrade, doped silicon isn't perfectly stable so semiconductor junction transistors will go bad one day, Schottky barriers will eventually contaminate. Chips built on larger processes and with thicker oxide layers will last longer, but none of them will last forever.