18 Jan
2015
18 Jan
'15
6:43 p.m.
On 01/18/2015 05:28 PM, Mouse wrote:
I'm probably just exposing my ignorance of the
8085 here, but did it
have anything like the prefix opcodes x86 has (repne et al)? I'm
wondering if it could be stuck doing something like (to admittedly try
to use syntax I don't really know) "repne cmp %ax,%ax" that would never
occur normally but might compute forever without fetching anything
further. Or, does it have a instruction prefetch buffer? (My guess
would be it's too old for that, but I don't really know.) If so, a
very tight loop might execute entirely out of the prefetch buffer....
None of that. Think of it as an 8080 with a few extra instructions, a
bit-bang serial I/O facility, and some extra vectored interrupt lines
and a TRAP interrupt--and +5 volt operation. Really, not even as
complex as a Z80.
--Chuck