Re: Chip-o-rama (was Re: Pentium II processor)

[Dave Martin <dpm_(_at_)_netcetera_(_dot_)_com>]

>On Fri, 18 Sep 1998 chuck_(_at_)_Yerkes_(_dot_)_com wrote:
>> x86 in general.  Still based on 8088, which was derived from the
>> Z80.

>Curious assertion.  Z80 was Zilog's souped up clone of an 8080.  I trace
>the 8088 back to the 8080, 8008 and 4004, but never thought of including
>the Z80 in the evolutionary stream.  Elaborate if you can.

If memory serves, the 8086 was Intel's attempt to remove (OK, relax) the
addressing limitations of the *8085* CPU and make it an even more wonderful
engine for running programs written in PL/M.  The 8085 had several
undocumented instructions that facilitated PL/M subroutine linkage and
other things that the 8080 got its HL register pair tied up in knots trying
to do.  The 8088 was just the 8086 with an 8-bit bus.

The Zilogians took a rather different tack on improving the 8080
architecture, primarily by adding more registers.  Take a smoking 4MHz Z-80
and TDL's Relocating Macro Assembler and you were styling, at the time...

The NMOS 8080 was itself a vast improvement over the PMOS 8008, although I
can't recall the specific instruction set differences.  The 4004 (and the
4040) were from another planet altogether...

If memory serves...


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Dave Martin                 Netcetera, Inc.            dpm_(_at_)_netcetera_(_dot_)_com
               "Infinity Welcomes Careful Drivers"
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