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Home▸ Forums▸ 68kMLA▸ 128K: bad RAM repair — #26
Post #26 by Gorgonops
Source Forum68kMLA
CategoryTroubleshooting
Post DateTue, 9 Nov 2010 - 17:29
Original URLhttps://68kmla.org/bb/threads/128k-bad-ram-repair.21576/
Post
Corrosion of the bonding wires hadn't occurred to me... that could well be a possibility. (Although I suppose you'd have to *very carefully* crack open the case of a dead DRAM and look at it under a microscope to really say if that's what is going on.) If it *is* some sort of internal corrosion that's killing these units it would seem that "Chip Rot" might a better name for it than "Bit Rot", given the conflict with the widely-used definition for the latter.

(IE, "Bit Rot" describes the data loss from aging or physical degradation, rather than being a technical term for a specific type of physical degradation process affecting the hardware. The only way the standard definition of "Bit Rot" applies to DRAM is the corruption of data in a "live system" due to soft errors, IE, bits flipped due to static discharges, alpha particles, cosmic rays, etc. Since DRAM doesn't retain data when powered off by design it cannot *itself* suffer from "Bit Rot".)

Anyway, seriously, I was curious if the term was being used specifically here to denote some manufacturing or process weakness widespread in chips of this age, and if there were a reference one could point to when "diagnosing" a failure of this type as "Bit Rot". Otherwise it doesn't seem like it's useful to diagnose these chip failures as such.

(I vaguely remember a term similar to "chip rot" being used in an article I read *many moons ago* in an 80's computer magazine to describe an age-related failure in early PROM chips, PROMs being programmable memories which store bits essentially by "blowing fuses" instead of retaining a charge like an EPROM. PROMs were widely used in early S-100 and other low production volume computer systems, and I *seem* to recall that the problem was traced to a "Tin Whiskers"-type phenomenon inside the packaging... but it's been far too long for me to remember specifically.)

mp.ls