[rc5] Re: Supercomputers & Bovine, Q&A

Sanford Olson sanford at msn.fullfeed.com
Tue Aug 5 01:28:51 EDT 1997


At 11:37 PM 8/4/97 +0200, Carsten wrote:
[snip]
>Ok, it is right that the instruction-set-architecture of the x86-chips
>is not the newest. Correct me if I am wrong, but isn't it so, that the
>Pentium II from '97 is still correctly executing 8085-programs from '77
>(I mean despite that the surrounding I/O is different)? It is impressive
>how fast they have made this architecture; it has still its solid place
>at the top with highest performing micro-processors. It has been claimed
>so often that the x86-technology is on the end of its development and it
>has never become true so far ...

Not that it matters, but you asked... :)   The 8085 is a single voltage
version of the 8080 8-bit processor.  The 8080/8085 had a horrible
archiecture - no relative branch instructions, thus no relocatable code and
only two memory operand address modes (immediate and HL register-indirect).
 The 8086 was a completely different design and totally incompatible with
8080/8085.  The 8086 was a pretty nice 16-bit processor for it's era (the
8088 16-bit/8-bit hack was used by the IBM PC).  Of course the Pentium is
actually not completely compatible with the 486 and earlier processors -
some 486 code had to be rewritten to run on Pentiums.

- Sanford



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