Partially-bad chips; was: repairing early HP calcs

Chuck Guzis cclist at
Mon Dec 19 19:52:21 CST 2005

On 12/20/2005 at 12:15 AM ard at wrote:

>I remember a UK company called Bi-Pak. They bought up defective ICs, 
>tested them [1], and sold them. They did sell things like TTL quad-gate 
>packages with only 3 good gates. Problem was, as we all found, those 3 
>gates quickly failed in use.

Back in the days when DRAM was precious, Intel had some "8Kx1" DRAMs that
were really "half good" 16K parts.  You used the "-x" digit to determine
which half to use.  I don't know if these were in general circulation, but
the sales engineers were passing them out to customers working on designs.
I may still have one or two kicking around that I found actually had 16K
worth of usable bits, providing they weren't run too fast.

And there was bubble memory with a flaw map.

Aren't some (or all) high-density DRAMs now made with extra rows and colums
to improve yields?


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