Extremely CISC instructions

Jon Elson elson at pico-systems.com
Mon Aug 23 21:43:57 CDT 2021

On 8/23/21 7:38 PM, Tom Stepleton via cctalk wrote:
> Hello,
> For the sake of illustration to folks who are not necessarily used to
> thinking about what computers do at the machine code level, I'm interested
> in collecting examples of single instructions for any CPU architecture that
> are unusually prolific in one way or another. This request is highly
> underconstrained, so I have to rely on peoples' good taste to determine
> what counts as "interesting" here. Perhaps a whole lot of different kinds
> of work or lots of different resources accessed is what I'm after. I expect
> these kinds of "busy" instructions were more common in architectures that
> are now less common, so perhaps this list is a good place to ask.

Well, you really need to look at VLIW architectures.  Very 
Long Instruction Word. See the Trace Multiflow for an 
example.  Every instruction had a load/store field, an 
integer arithmetic field (for address calculations) and a 
floating point field.  For more money, you added boards and 
there were more of these fields in the instruction.  There 
was no cache, the compiler moved the address calculation and 
the data fetch sufficiently far up the code so the data 
would be available when needed.


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