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

[Josh Dersch]

On Wed, Sep 7, 2016 at 3:43 PM, CuriousMarc <curiousmarc3 at gmail.com> wrote:

> > > On Sep 5, 2016, at 9:30 AM, Josh Dersch <derschjo at gmail.com> wrote:
> > >
> > > At the LCM, I used an Apple II to test out the Alto's memory -- the
> > > Alto II XM uses 4116 RAM chips.  I swapped in a row at a time and wrote
> a
> > > little BASIC program to test for obvious errors.  This was
> > > time-consuming, but eliminated the obviously bad chips, which helped
> immensely.
> >
> > Oh, that's so simple and clever! Are these 16k chips? I don't have an
> Apple II,
> > but I wonder if I could use the same trick and plug them in my HP 85
> > for which I just managed to burn the service ROM, which has a memory
> > test built in.
>
> Josh,
> I checked, and the mysterious HP 1818-1396 or 1818-0341 RAM chips used in
> the HP-85 appear to be NEC uPD416-2 or MOSTEK 16k chips. They appear to be
> pin for pin, voltage and speed compatible with the MOSTEK 4116-3 used in
> the
> Alto. So it looks like I could check the Alto Xerox II-XM RAM chips on my
> HP-85.
> 8 at a time, that might take a while :-). Thanks for the tip, I'd never
> have
> thought about it!
> Marc
>
>
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