vintage computers in active use

jwsmobile jws at
Thu May 26 21:55:10 CDT 2016

On 5/26/2016 2:25 PM, Jay West wrote:
> Of course, this p-code was executed
> interpretively. By missionary instructions;)
On the microcoded machines, the 1600 and Ultimate (honeywell level 6, 
and also custom bit slice microengines) systems in particular, the 
interpreter was assisted by a macro instruction which essentially 
implemented the jump to a table based on the next p instruction pointed 
at by the p-code instruction counter.

At the end of the pick assembly code (which was executed by firmware) 
the special instruction was executed in the stream of pick assembly 

Later versions implemented execution of 8 or 10 instructions directly in 
the firmware, so sometimes when some versions of the firmware came out 
it was not just a branch to code to execute all the p-code, but 
sometimes a lot of pcode would be executed by the firmware, eventually 
coming up for air and back to some pick firmware when a non firmware 
instruction was encountered.  A very interesting mix of executing code 
at both the macro level and micro level.

for completeness of this, if I've not lost you, there was a machine 
built by Pick which was also microcoded, and as far as I know those were 
the only microcoded machines for pick.

The above concept worked in varying degrees with the cross compiled 
systems which ran on 68000 and other machines as well.

More information about the cctalk mailing list