Y Combinator is restoring one of Alan Kay's Xerox Alto machines

Adrian Graham binarydinosaurs at gmail.com
Fri Sep 9 03:35:04 CDT 2016

Apropos of 4116 RAM chips over the last 8 or so months I've restored 4 CBM
PETs, 3 Apple ][s and a few Sinclair ZX Spectrums. All these use either
4116-2 or 4116-3 (or can use either as long as they're matched in 8s) and
they've all had one or more RAM failures.

I built a rudimentary chip tester using a Spectrum board that I fitted a
small ribbon cable and ZIF socket to the end-most lower RAM chip location
and replaced the BASIC PROM with a diagnostic EEPROM so all I need to do is
power up with the suspect chip in the ZIF socket and it gets tested with
the other 7.

It's not an exhaustive test at all but like all other 4116 based machines
it needs 8 good ones to boot so it might be worth making such a thing for
the Alto.


On 9 September 2016 at 09:15, <curiousmarc3 at gmail.com> wrote:

> > On Sep 7, 2016, at 4:18 PM, Josh Dersch <derschjo at gmail.com> wrote:
> >
> > Yep, the NEC uPD416D's are what we have in the Alto we recently restored.
> > And yeah, it takes awhile, but it's worth the effort :).
> >
> > Have fun!
> > - Josh
> Out of curiosity, did you find any bad RAM chips in your system? If so,
> how many? I had only one bad one in one of my HP 85 (out of 8), but it
> definitely happens.
> Marc

Owner of Binary Dinosaurs, the UK's biggest home computer collection?

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