Re: a dozen cpu's on a chip

On Sat, 10 May 2008 00:04:22 -0400, krw <krw@xxxxxxxxxxxxxxxx> wrote:

In article <9f2a24lb3qdd4fplttffo6oarcbgqc952v@xxxxxxx>,
jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx says...
On Fri, 9 May 2008 22:27:56 -0400, krw <krw@xxxxxxxxxxxxxxxx> wrote:

In article <3n6624pu6762nup9apu3crj5vh1uu6fqbn@xxxxxxx>,
jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx says...
On Thu, 8 May 2008 07:42:04 -0700 (PDT), MooseFET <kensmith@xxxxxxxxx>
wrote:

On May 7, 7:48 pm, John Larkin
<jjlar...@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
http://www.eetimes.com/news/latest/showArticle.jhtml;jsessionid=CESEX...

I bet we'll see 256 one of these days.

When you get to large numbers of CPUs it seems to make sense to stop
making them identical. For servers this would be doubly so. Many of
the CPUs won't need to do floating point operations.

Right. Amybe a few cpu's would have serious floating point power, or a
few separate fp engines could be assigned to cpu's as needed. Lots of
cpu's, doing stuff like file i/o or serial stuff, could be less
powerful. I suppose we'll always need special graphics hardware, but
just a few of those per chip.

Asymmetric multiprocessing makes the scheduler's life more
complicated. Since the scheduler is part of the OS, and the OS is
most often M$, this isn't a good idea, IMO. ;-) Hardware is cheap
(so cheap PowerPC is including decimal FPUs). Throw the FPU on
every node, whether its needed or not.

It also would make sense to do things like memory moves in the "Memory
Mismanagement Unit" since the values don't need to be modified on the
way through.

This will make it a lot harder to say how many CPUs are in a chip. If
there is only as much hardware as 200 full CPUs but 500 threads can be
running at the same time, do you call it 200 or 500 CPUs.

Next step is to get rid of task swapping and threads altogether. One
CPU is the OS, and one cpu gets assigned per process.

Which negates what you say above. Running a task, then getting an
exception because you don't have an instruction you thought you had
is expensive.

Why would you get an exception? If a device driver doesn't need fp
opcodes, run it on one of the many cpu's that doesn't have floating
point. And vice versa. <> rocket science.

You're making your scheduler's job more difficult and limiting
flexibility. Computer architecture is rocket surgery.

A bunch of cpu's don't need scheduling like a single-processor os
does; individual cpu's do their thing concurrently and set semaphores,
and go idle, if they finish whatever they are assigned to do. And
besides, the task manager cpu doesn't have anything else to do. The
scheduler will mostly set up things like memory management and
priviliges and assignments and turn them loose, rather than
frantically swapping them in real time. When everything runs
simultaneously, priorities become less important. It's a whole new way
of thinking.

The IBM Cell chip is an architecture that trends in that direction.

Current hardware and software has been driven by Intel's silicon
process skill (and their vicious lack of ethics) and by Microsoft's
thousands of programmers (and their vicious lack of ethics) but not by
any particularly intelligent planning. Most big software apps are
spinning-out-of-control crapware with gigabyte service packs just
pushing the bugs around. It's time for a change, for the next
generation of computing, and I think it will happen when there are so
many processors on a chip that multitasking quits making sense.

A new language wouldn't hurt either.

John


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Relevant Pages

  • Re: a dozen cpus on a chip
    ... ;-) Hardware is cheap. ... This will make it a lot harder to say how many CPUs are in a chip. ... Computer architecture is rocket surgery. ... priviliges and assignments and turn them loose, ...
    (sci.electronics.design)
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    ... libraries that help programmers make use of the co-processing features. ... keep in mind some of the main downfalls of any hardware based co-processor: ... specialized hardware than to just burn CPUs cycles to perform the search. ...
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  • Re: FPGA-based hardware accelerator for PC
    ... FPGAs and standard cpus are bit like oil & water, don't mix very well, ... General purpose CPUs for the things they're good at like data IO, ... you can put software & hardware much closer to ... One can even model the whole thing in a common language ...
    (comp.arch.fpga)
  • Re: FPGA-based hardware accelerator for PC
    ... FPGAs and standard cpus are bit like oil & water, don't mix very well, ... General purpose CPUs for the things they're good at like data IO, ... you can put software & hardware much closer to ... One can even model the whole thing in a common language ...
    (comp.arch.fpga)
  • Re: OT: CPUs
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