And speaking of ALGOL

[ben]

On 8/11/2015 3:13 PM, Noel Chiappa wrote:
>      > From: Paul Koning
>
>      > Every machine needs a fast memory system. CISC machines just as much,
>      > after all the number of memory references per operation of a given kind
>      > doesn't depend on the sort of CPU architecture you use.
>
> You're forgetting the memory bandwidth for the instruction fetching. RISC
> machines execute a stream of simple, low-level instructions, whereas CISC
> machines tend to do fewer, (semantically) higher-level operations - and in
> the process, use less memory bandwidth for instructions.
>
> To be tedious (sorry), for example, instead of of the RISC instruction
> sequence 'move register Ra to Rt1; add constant X to Rt1; move mem loc (Rt1)
> to Rt2; add Rn to Rt2; move Rt2 to mem loc (Rt1)', a CISC would just do 'add
> Rn to mem loc X[Ra]'. Same number of _data_ reads/writes, but a very different
> count of instruction fetches.
>
> The CISC tradeoff (fewer, slower, instructions) made sense 'back in the day',
> and not just for memory bandwidth - it made for more compact code, back when
> memory was in very short supply (by today's standards).
>
> Now, of course, a number of technological changes - primarily multi-level
> caches - have changed the 'sweet spot' for optimal instruction complexity,
> while keeping the memory bandwidth needed for instruction fetches down.
>
> 	Noel

But the real question is your programming model again.

It all seems to be the old FORTRAN model. Random access of
any variable from absolute address.  /common/ FOO(100),i,j,BAR(100)
... sum = FOO(j)+BAR(i-6)...

Ben.