26 Dec
2010
26 Dec
'10
1:18 a.m.
From: eric at brouhaha.com
Chuck Guzis wrote:
Hi
It seemed like I recalled the NEC 8080's had some extras but it
must have been brain rot on my part. I have one of their 8080's
in my Poly88. It is quite easy to single step with this computer
and display all the registers, memory pointed to by double
registers and flags. I found nothing unusual happening on any
of the other unused instructions. I have a newer AMD8080 I guess
I could try some day.
The Poly88 had one of the best software monitors I've ever
seen on an early uP system.
Dwight
To the best of my recollection, the undocumented
8080
opcodes are, by and large, no-ops or redundancies (i.e. they do the
same as a close-valued opcode probably from incomplete PLA decoding).
[...]
No startling new "triple precision
divide" instructions.
I wasn't expecting any. The reason I'm asking is to be able to
replicate the behavior in a simulator, in case any software happened to
use them (intentionally or otherwise).
Eric