Partially-bad chips; was: repairing early HP calcs
ajp166 at bellatlantic.net
Mon Dec 19 20:03:43 CST 2005
>Subject: Re: Partially-bad chips; was: repairing early HP calcs
> From: "Chuck Guzis" <cclist at sydex.com>
> Date: Mon, 19 Dec 2005 17:52:21 -0800
> To: cctalk at classiccmp.org
>On 12/20/2005 at 12:15 AM ard at p850ug1.demon.co.uk wrote:
>>I remember a UK company called Bi-Pak. They bought up defective ICs,
>>tested them , 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.
Polypaks was the place here. No bargan as usually a package with one bad
gate developed other problems over time.
>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.
I used to have a full set of half good 64ks, likely still do.
>And there was bubble memory with a flaw map.
That was normal. It had extra tracks for that reason. I must have 8
of the BMs and two working BPK72 boards. There was no such thing as
a flawless BM apparently.
>Aren't some (or all) high-density DRAMs now made with extra rows and colums
>to improve yields?
Used to be so, don't know about it now.
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