Date   : Mon, 10 Oct 1983 11:53:00 PDT
From   : MMOON.ES@PARC-MAXC.ARPA
Subject: Re: 85/88

The info I have from National says the NSC800 is *not* pin compatible
with the 8085.  This is more than a mere rearrangement of corresponding
signals to different locations; while the address/data and intererupt
busses have corresponding pinouts, the other signals have a z80 flavor.
I am most interested in maintaining IEEE-696 timing, as well as the
"16-bit" upgrade, so I must do a good timing analysis before a
piggy-back could be designed.  Furthermore, their is serious doubt, if I
read the literature correctly as to the TTL compatibility of the NSC800,
at least at full speed.  The levels required to assure logic 1 and logic
0 on this CPU's inputs look like they may stretch the slew rates of the
interfacing TTL in the worst case.  Still got to think about that one.
The information I have is on the 4 Mhz version of this device & while I
may *call* National's rep, could be 2001 before I get any reply.
Therefore this message is heeaded for netland, in the hopes someone else
has looked at this very tempting possibility, and to keep Rumour Control
from propagating the mistaken (unfortunately) notion that the Nsc800 is
a drop-in-and-go replacement (just in case somebody is following this
enquiry with like intentions).

               MMoon.es