Intel 8085 - interview?

allison allisonportable at
Fri Feb 9 14:26:53 CST 2018

On 02/09/2018 12:23 PM, Chuck Guzis via cctalk wrote:
> On 02/09/2018 05:22 AM, allison via cctalk wrote:
>> Also all of the competitors and second sources that made 8085s had the
>> added instructions.  The are indeed handy too.
> Calmos (then later Tundra) Semiconductor actually documents them in
> detail in their CA80C85 datasheet, but those were from the early 1980s.
> What was interesting was that even through we were working pretty
> tightly with Intel in 1976, not a word of the added instructions was
> uttered by our sales guy, "Fast Eddie", who usually was pretty well
> informed about the goings on over in Santa Clara.   Bill Davidow was on
> our BOD as well.
> That's a shame; we could have used those instructions too.
> --Chuck
Interesting story the NEC 8085A was a reverse engineer and was faithful to
the then (pre 1980) hidden instructions.  NEC learned hard form the 8080
as it was not compatible (they belived the datasheet) and would lead to the
8080AFC (A version, fully compatable).

If anyone didn't that's a first as every part I could get did at least
after 1978.

I new of the instruction back in 78-79 when I got a Netronics Explorer85
(8085 powered with a short s100 bus).  I bought and built it to play with
8085 and the magic instructions.

IBM PC early also did that... other vendors of the 8088 didn't work in the
64K and early 256K IBM PCs due to a slight timing variation that
reputedly intel helped design in.  One gate fixed it but it was undocumented
thing you could getaway with only with Intel 8088s.

The industry was loaded with that the 6502 series also had that going on
as well as the 6809 and others.


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