🚀 go-pugleaf

In article <3098@scolex.sco.COM> seanf@sco.COM (Sean Fagan) writes:

> In article <405@ctycal.UUCP> ingoldsb@ctycal.COM (Terry Ingoldsby) writes:
> >Does anyone know which of the CISC microprocessors are microcoded
> >and which are hardwired?  I would expect the older (simpler) units
[...]
> Chips such as the SPARC, 88000, ARM, MIPS series, and the 6502 do not have
> microcode; they are hardwired.  This really has nothing to do with how new

Are you sure the 6502 isn't microcoded?  I built a ttl 6502 (6507
actually) emulator as a digital design lab project in college, and it
had to execute each instruction in the same number of cycles as the
real thing in order to be able to plug into an Atari 2600 video game
as the demo.

Our implementation decoded the instruction into two parts.  One
controlled the datapaths and the other selected one of a couple of
dozen microprograms.  The number of steps needed for each microprogram
exactly matched the cycle count of the real chip.  Our design was
based on analyzing the instruction set, not on any internal design
documentation.  I've since been interested in knowing if this is how
the real chip is implemented.
-- 
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