Sparc desktop vs x86 desktop

Cameron Kaiser spectre at floodgap.com
Thu Oct 16 07:54:24 CDT 2008


> > If sheer CPU crunch is your only criterion (not not NOT, dammit,
> > "criteria"![%]), sure.

> Sorry, Jay, but I'm going to mention cars ;-)
> I always thought that x86 arch seemed more "revvy" and SPARC seemed more 
> "torquey" if you can think of it in those terms.  Something like x86 
> seems better for doing a couple of things very very quickly, where with 
> a SPARC it wasn't that fast to begin with, but you can pile on the load 
> without it slowing down.

I like the first sentence for the analogy -- not so fond of the second.
Particularly for the deeply pipelined later x86en, individual pipeline
steps are fast (thus "revvy" I think is apt) but it suffers like any
pipeline from bubbles due to bad branches and so on, and being deeply
pipelined suffers more. SPARC, and particularly POWER/PowerPC, can't rev
clock speed like that because each step of the pipeline is doing more, but 
their shorter lines are more resistant to misprediction. Chips like the
G4 also can be made very power-efficient because you're not grinding clock.

It's more of an efficiency question than a load tolerance question, IMHO.

<OT>
As an example of how to do this wrong, the G5, which tried to ramp up clock
by adopting Intel's approach, became a power hungry monster (as I listen to
my Power Mac G5 quad whine) and I'm sure directly contributed to Apple going
Intel since the G5 could never have made it into a laptop as originally
designed.

The nadir of Intel's fascination with super duper pipelines was Netburst and
putting all their eggs into ramping up clock speed and building better
speculative logic. This did pay off in marketing, but given their switch to
Core, Intel appears to have realized that NetBurst was not sustainable.
Indeed, the pipeline is half the size of Prescott's.
</OT>

-- 
------------------------------------ personal: http://www.cameronkaiser.com/ --
  Cameron Kaiser * Floodgap Systems * www.floodgap.com * ckaiser at floodgap.com
-- Heisenberg may have been here. ---------------------------------------------



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