[rescue] I/O coprocessors?

[Dave McGuire]

On Saturday, March 1, 2003, at 09:25 PM, Scott Newell wrote:
> Legend has it that the popular Microchip PIC series microcontrollers 
> are
> derived from an old General Instruments I/O coprocessor designed for a 
> 16
> bit microprocessor.

   Almost...The PIC traces its lineage back to the General Instrument 
8X300 family of microcontrollers.  It's a true microcontroller, not 
really an I/O coprocessor.  Indeed. GI spun off its semiconductor 
division which became Arizona Microchip, or just Microchip...the source 
of PIC processors.  The architecture remains largely unmodified.

   The 8X300 and the later 8X305 were very popular in intelligent disk 
controllers for minicomputers like PDP11s.  They didn't displace the 
"pair of 2901s and a 2910" setup that many designers used, but they 
were popular nonetheless.

>   I have a textbook that refers to the Intel 8089 as an
> I/O processor for use with 8088/8086 based systems--strange little 
> beast.
> Did anyone actually use the 8089?  (I don't think I've ever seen one.)

   I've got at least one of every popular (and not so popular) chip used 
from the dawn of integrated circuitry up into the late 1970s...and I've 
never even *seen* an 8089.  I've read a lot about them though, and I 
agree, it's a strange beast.  Almost mainframe-esque in its 
capabilities.

> Are there other microprocessor families with dedicated I/O processors?
> Moto 68k?  Zilog?

   I don't know of any in either of those families.  Dedicated I/O 
processors seem to be limited to the mini/mainframe world.

       -Dave

--
Dave McGuire             "I've grown hair again, just
St. Petersburg, FL           for the occasion."       -Doc Shipley