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Dual Core - Is this a battle AMD can win?

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November 19, 2004 3:37:26 PM

Archived from groups: comp.sys.ibm.pc.hardware.chips (More info?)

I got thinking about the impact to dual-core technology and whether
AMD has painted itself into a corner.

AMD wins points for the "coolness" factor of announcing the first x86
dual-core. They already won points for 64bit, not that it is useable
outside linux at this point. BUT... I wonder if this is the best
approach.

My concerns with dual-core:
1) Two CPU's aren't as efficient with the resources as one. Dualie
systems are only ~60% better performing over a single core.
Admittedly dual-core systems are different beasts here, but it is
certainly not going to be 2x performance.

2) Huge impact on the die per wafer yielded. In addition to fewer
available units, any defect that kills one of the dual CPUs will kill
the unit as a dual-core.

It is really (2) that bothers me, especially since we are talking
about going to mainstream desktop dual-core systems. Although AMD has
partnered with IBM and Chartered, the overall 300mm capacity for AMD
is significantly less than Intel which has 4 300mm fabs online now and
another in retro. Intel can bury AMD in silicon.

AMD has had better CPU designs, which has allowed it to gain
marketshare in mainstream and server space. I wonder why AMD did not
leverage their design teams to engineer a better solution than a
seeming "desperate" switch to dual-core. Doesn't this move play into
Intel's capacity advantage?

-Greg
Anonymous
a b à CPUs
November 20, 2004 2:11:43 AM

Archived from groups: comp.sys.ibm.pc.hardware.chips (More info?)

On 19 Nov 2004 12:37:26 -0800, jgmillr1@yahoo.com (Greg) wrote:

>I got thinking about the impact to dual-core technology and whether
>AMD has painted itself into a corner.
>
>AMD wins points for the "coolness" factor of announcing the first x86
>dual-core. They already won points for 64bit, not that it is useable
>outside linux at this point. BUT... I wonder if this is the best
>approach.
>
>My concerns with dual-core:
>1) Two CPU's aren't as efficient with the resources as one. Dualie
>systems are only ~60% better performing over a single core.
>Admittedly dual-core systems are different beasts here, but it is
>certainly not going to be 2x performance.

Depends on the task(s) of course but if that 60% is an "average" figure,
expect it to improve. For mainstream computing, programmers will adapt to
make gains and there are already numerically intensive & DP tasks which
yield >100% efficiency on dual and higher multiple cores. Besides that,
there is the system response you get with dual, which *is* appreciated by
even the desktop market.

>2) Huge impact on the die per wafer yielded. In addition to fewer
>available units, any defect that kills one of the dual CPUs will kill
>the unit as a dual-core.

I have to assume the "model" has been studied in detail and it "works" -
there'll always be a low-end Celeron/Duron-Sempron.

>It is really (2) that bothers me, especially since we are talking
>about going to mainstream desktop dual-core systems. Although AMD has
>partnered with IBM and Chartered, the overall 300mm capacity for AMD
>is significantly less than Intel which has 4 300mm fabs online now and
>another in retro. Intel can bury AMD in silicon.

By the time we get to duals, AMD will have their exisitng Dresden, plus the
new 300mm there, as well as the foundry deals. Even if they're targeting
say 30-40% market share, I'd think they will have sufficient capacity.

>AMD has had better CPU designs, which has allowed it to gain
>marketshare in mainstream and server space. I wonder why AMD did not
>leverage their design teams to engineer a better solution than a
>seeming "desperate" switch to dual-core. Doesn't this move play into
>Intel's capacity advantage?

If you believe the talk of "the end of scaling", and that is the line from
some top industry insiders, short of a major leap in technology, where else
is there to go but dual cores? I'm not sure that the K8 is really that
much better a CPU "design" than the Pentium-M; Intel just went off on its
P4 adventure and it looks like it will now self-correct.

Intel is getting some mileage out of Hyper Threading and I haven't heard
talk of AMD following so, in a sense, dual is AMD's answer there.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??
Anonymous
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November 20, 2004 7:59:44 AM

Archived from groups: comp.sys.ibm.pc.hardware.chips (More info?)

On 19 Nov 2004 12:37:26 -0800, jgmillr1@yahoo.com (Greg) wrote:
>
>I got thinking about the impact to dual-core technology and whether
>AMD has painted itself into a corner.
>
>AMD wins points for the "coolness" factor of announcing the first x86
>dual-core. They already won points for 64bit, not that it is useable
>outside linux at this point.

And *BSD and Solaris... Basically everyone other than Microsoft, who
were supposed to have their 64-bit OS out over a year ago, but like
everything else Microsoft does, it's horribly late.

> BUT... I wonder if this is the best
>approach.
>
>My concerns with dual-core:
>1) Two CPU's aren't as efficient with the resources as one. Dualie
>systems are only ~60% better performing over a single core.
>Admittedly dual-core systems are different beasts here, but it is
>certainly not going to be 2x performance.

Sure, but what the heck else are you going to do with all the die
space?!

>2) Huge impact on the die per wafer yielded. In addition to fewer
>available units, any defect that kills one of the dual CPUs will kill
>the unit as a dual-core.

Sure, but again, what the heck else are you going to do with all that
die space?

Take the example of Intel's Northwood vs. Prescott. Intel more than
doubled the number of transistors. If the two chips were built on an
equivalent process, the Prescott would be SIGNIFICANTLY larger than
the Northwood, and yet in the end it resulted in almost non-existent
performance gains. Why? Because we're rapidly hitting a point of
diminishing returns for these chips. Even if you throw a TON more
execution units and decoders and various other widgets, you tend to
only get a pretty small increase in performance. We've apparently
reached the stage now where doubling these things results in very
small improvements in performance. The main problem here being that
memory latency has skyrocketed relative to a processors raw number
crunching ability.

There are a few solutions here. First and most simple is adding more
cache, but that only gets you so far and eventually wears out as well.
The second is do to some sort of multithreading. Good for some
situations, but it bites you in the ass on others. The final solution
is to go dual-core.

>It is really (2) that bothers me, especially since we are talking
>about going to mainstream desktop dual-core systems. Although AMD has
>partnered with IBM and Chartered, the overall 300mm capacity for AMD
>is significantly less than Intel which has 4 300mm fabs online now and
>another in retro. Intel can bury AMD in silicon.

Going to dual-cores only roughly doubles the number of transistors
used in a chip, and doubling the number of transistors used in a chip
every 18-24 months has been standard-fare for the past 30 years or so
(Moore's law and all). Designers simply have to look forward and say
"what is the best way that we can spend the number 2x increase in
transistors". There are lots of options, but I think pretty much all
designers have come to the conclusion that, at this stage at least,
going to dual-cores is the best option.

Remember, dual-core 90nm chips are roughly the same size as
single-core 130nm chips. Same goes for 65nm vs 90nm.

>AMD has had better CPU designs, which has allowed it to gain
>marketshare in mainstream and server space. I wonder why AMD did not
>leverage their design teams to engineer a better solution than a
>seeming "desperate" switch to dual-core. Doesn't this move play into
>Intel's capacity advantage?

One could easily argue that it is just the opposite. AMD increased
the number of transistors in the Opteron nearly 3-fold from the
AthlonXP (Thoroughbred at least). How much performance did that gain
them? How much additional performance would an additional 2-fold
increase in performance given that they've already used up their
integrated-memory-controller card? An extra 10%? 5%? Less?

If AMD wanted to go head-to-head with Intel in single-core
performance, Intel could potentially just throw a LOT more die space
(ie for cache) at their solution. Case-in-point, the new P4's that
have 2MB of L2 cache (first one just appeared as an official Intel
part earlier this week).

Relative to bumping up single-core performance, going dual-core is
pretty cheap (die-space wise) way of gaining performance.

-------------
Tony Hill
hilla <underscore> 20 <at> yahoo <dot> ca
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Anonymous
a b à CPUs
November 22, 2004 11:40:33 AM

Archived from groups: comp.sys.ibm.pc.hardware.chips (More info?)

jgmillr1@yahoo.com (Greg) wrote:

>I got thinking about the impact to dual-core technology and whether
>AMD has painted itself into a corner.

I don't see how could have "painted itself into a corner". It's not
like they're going to stop producing single-core CPU's.

>AMD wins points for the "coolness" factor of announcing the first x86
>dual-core.

Announcements aren't cool. Show me the silicon.

>(snip)
>
>AMD has had better CPU designs, which has allowed it to gain
>marketshare in mainstream and server space. I wonder why AMD did not
>leverage their design teams to engineer a better solution than a
>seeming "desperate" switch to dual-core. Doesn't this move play into
>Intel's capacity advantage?

It's hardly "desperate". It's more like "an obvious thing to do, at
the high end". My prediction is that dual-cores will be marketed as a
very expensive, high-end solution, out to a few years from now. This
will solve all of the "yield" issues that you raised - they'll just
charge more to compensate.
Anonymous
a b à CPUs
November 22, 2004 2:48:46 PM

Archived from groups: comp.sys.ibm.pc.hardware.chips (More info?)

jgmillr1@yahoo.com (Greg) wrote in message news:<58bf032b.0411191237.6e7633d3@posting.google.com>...
> 1) Two CPU's aren't as efficient with the resources as one. Dualie
> systems are only ~60% better performing over a single core.
> Admittedly dual-core systems are different beasts here, but it is
> certainly not going to be 2x performance.

AMD's existing multiprocessors are getting around 80% scaling
efficiency according to some HPC tests. And it's scaling efficiency is
maintained from 2 processors all of the way upto its maximum limit of
8 processors; it doesn't drop off in efficiency the more processors
that you add. That's mainly due to the point-to-point Hypertransport
bus.

A dual-core should scale up with even more efficiency since the
internal short-distance HT links are going to be much faster than the
external long-distance HT links.

> 2) Huge impact on the die per wafer yielded. In addition to fewer
> available units, any defect that kills one of the dual CPUs will kill
> the unit as a dual-core.

It might kill it as a dual-core true, but half of it might still be
salvageable as a single-core chip. They are using the same socket
whether it's single- or dual-core.

> It is really (2) that bothers me, especially since we are talking
> about going to mainstream desktop dual-core systems. Although AMD has
> partnered with IBM and Chartered, the overall 300mm capacity for AMD
> is significantly less than Intel which has 4 300mm fabs online now and
> another in retro. Intel can bury AMD in silicon.
>
> AMD has had better CPU designs, which has allowed it to gain
> marketshare in mainstream and server space. I wonder why AMD did not
> leverage their design teams to engineer a better solution than a
> seeming "desperate" switch to dual-core. Doesn't this move play into
> Intel's capacity advantage?

I'm sure Intel is hoping so. In fact, I've even speculated that Intel
might just try to produce a large percentage of dual-cores and just
relabel failed dualies as singulars. It's got five 300mm plants, and
it's got an overcapacity problem, so it's got lots of factories that
it needs to keep busy.

On AMD's side, it has the advantage of designing for dual-cores well
ahead of time, therefore it now has enough time to tweak its
manufacturing process until it is really efficient. So that it doesn't
need to waste any chips in a brute force fashion.

Yousuf Khan
!