RE: F21/P21 "improvements" | memory cost

[kr@xxxxxxxxxxx]

> Chuck has said that on chip memory is generally speaking expensive
> compared to memory chips for the above reasons.  Figure out what
> percentage of most big processors are on chip cache and what
> percentage of the cost it is and you see what he means.

so what are the numbers actually ?  have you figured this out ?

are you basically saying that because a large amount of chip real
estate on an (expensive) intel processor goes towards cache means that
this memory is very expensive in absolute terms ?

if yes, i would find that this reasoning gets it the wrong way
around.  fact is: fast processors have to deal with the classic
von-neumann-bottleneck, which occurs because large memory banks tend
to be a lot slower than CPU logic.  short of very radical changes,
there is currently no easy way around this.

this problem is dealt with by various caching strategies.  in other
words, a lot of the transistors (which you might call "bloat") on a
modern fast CPU chip are devoted to these "logistics" problems of
shoving instructions and data in and out of the CPU with as little
delay as possible.  while this "overhead" is not directly involved in
the "real" computations that the CPU is supposed to be doing, it is
nevertheless essential to sustain high bandwidth.  in some sense, the
whole RISC paradigm of needing streams of a lot of simple instructions
in place of fewer complex ones has only exacerbated this problem.  it
is probably even worse for a MISC approach.

the problem that a chip like the F21 has is that it lacks all this
essential memory-interface-infrastructure, which means that while the
core CPU might be bloody fast, it chokes instantaneously as soon as
needs to fetch any kind of data or instruction from memory.  while the 
folks behind the F21 seem to dismiss the need for the complexity of
on-chip memory and caching, it seems like the F21 is limited by
exactly the same problem, and no great alternative solution has been
demonstrated either.

does chuck moore ever read this mailing list, and if not, why not ?

-- 
greetings
markus krummenacker