70's computers

[ben]

On 10/24/2018 9:47 AM, Grant Taylor via cctalk wrote:
> On 10/24/2018 07:01 AM, Noel Chiappa via cctalk wrote:
>> An observation about RISC: I've opined before that the CISC->RISC 
>> transition was driven, in part, by the changing balance of CPU speed 
>> versus memory speed: with slow memory and fast CPUs, it makes sense to 
>> get as much execution bang out of every fetch buck (so complex 
>> instructions); but when memory bandwidth goes up, one needs a fast CPU 
>> to use it all (so simple instructions).
> 
> Maybe I need to finish my coffee before posting, but here goes anyway....
> 
> I thought memory and CPU speed used to be somewhat comparable 
> historically.  And that such is NOT the case now.

Statements made here may or may not reflect having morning coffee.
Back then it was throwing floating point numbers around, now it is 
pixels at high speed. Regardless of the data, most of the time
(assuming simple hardware) you spend more time calculating the
effective address of data getting the data itself.
A RISC machine may have better space to cache stuff,but inside
knowledge how memory gets to the alu units from main memory was
visible until just a few years ago.
we have the NEW intel 800086 20% faster on benchmarks,using
C+++ MOO-GNU compiler. (Fine print older may have  a 200% loss
of speed in some applications, re-compile with the latest (never
released to the public software) written in Chinese.*
I have no idea what is in a modern home computer, but I suspect
it still follows the same design of the IBM PC. Single CPU
with segmented memory and bit of DMA here and there.
Computer Science models are from the transistor era of computing
but don't reflect the internal speeds in the cpu chips.
To me they reflect the vacuum tube model of computing. Time to re-think 
again.

Ben.
* if it was real fine print, I need a lawyer to read it.