[time-nuts] favorite microcontroller module?

Chuck Harris cfharris at erols.com
Thu Feb 21 20:38:58 UTC 2008


Mike S wrote:
> At 10:17 AM 2/21/2008, Chuck Harris wrote...
>> Sorry, but that is not so.  The 68000 was a 16 bit machine, both 
>> internally, and externally, with 32 bit registers and some 32 bit 
>> instructions.
> 
> Your Intel bias is really showing now. Enough with trying to change the 
> subject. The discussion was in regard to architecture, not 
> implementation.
> 
> Your original claim was "It would have been impossible for intel to put 
> a 32 bit bus and register set on a processor like the 8086 back in 
> 1978." That was in support of Intel's segmented memory _architecture._
> 
> That claim is disproved by the fact that the 68000, which first shipped 
> in 1979, had a 32 bit architecture.

But not a 32 bit bus (as you have quoted me (above) saying was impossible).
The parallel bus structure, with all of its attending registers, ALU's, and
wiring is what was beyond Intel, and Motorola in 1978 and 1979.  They just
couldn't make a die that big, and meet the needed reliability, heat removal,
and cost requirements of a successful commercial processor.

You have my words right there, but for some reason you felt the need to
misrepresent them.

I liked programming on Motorola 68020's.  It was easy, and I never felt
like I had to work at all to solve a problem.  But at the same time, it
was glacially slow.  We got significantly better performance with the same
programs running under the 386 and 486 processors of the day.  The compilers
made smaller code for the intel processors than they did for the Motorola,
and the Motorola lost all of the benchmarks we ran.  We were undoubtedly
running the wrong benchmarks, and using the wrong compilers, but they were
representative of what we needed done.

  That the first implementation
> didn't bring everything at once is beside the point. The programming 
> model was 32 bit, which very significantly distinguishes it from the 
> 8086 architecture. Perhaps you want to call the 8088 an 8 bit 
> processor?

No, I would call it a mistake, but that is just me.  I put a number of
8086's in designs, but never an 8088.  I used fast Z80's instead.  One
of my all time favorite embedded intel processors was the 80C186.  It was
powerful, small, and easy to integrate into designs.

> 8086: 16 bit registers, 16 bit data bus, 16 bit addressing with 
> segmentation extensions.
> 8088: 16 bit registers, 16/8 bit data bus, 16 bit addressing with 
> segmentation extensions.
> 68000: 32 bit registers, 32/16 bit data bus, 32/24 bit linear 
> addressing.
> 68008: 32 bit registers, 32/8 bit data bus, 32/20-22 bit linear 
...


-Chuck Harris




More information about the Time-nuts_lists.febo.com mailing list