Partially-bad chips; was: repairing early HP calcs

[Allison]

>
>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 [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.

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.

Allison