Partially-bad chips; was: repairing early HP calcs

[Tony Duell]

> 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

There were certainly 32K*1 DRAMs that were half-good 64K chips. IIRC at 
least one version of the 48K Spectrum used them, and there was a link on 
the board to select which half would be used (obviously all 8 chips had 
to be of the same type). I suspect the CoCo1 used them too.

-tony