BM Seer Unofficial thoughts from an anonymous Sun employee

AMD, Intel, TDP, ACP...way too much on CPU, what about the system?

Friday Sep 14, 2007

I know AMD & Intel love to focus on the power used by CPUs in their high-stakes battle to gain server chip dominance. Both started talking TDP (Thermal Design Power) and getting people to judge systems based on TDP.

...wait a minute, buying a system based on the power of a CPU is a bit of misdirection unless the CPU is most of the power. This isn't the case any more. So CPU TDP should be ignored, unless you are designing your own product and are just buying CPUs.

First of all system power is what datacenters care about, so Intel and AMD should be talking about system power in realistic memory configurations. Memory draws lots of power these days.

Second,TDP was created so the manufactures of servers manufacturers would know much power the chip consumes in worst-case maximum-power cases so they could design power supplies, cooling, etc. That just isn't useful to datacenter managers.

AMD's marketing only slightly improved the situation by telling customers of SYSTEMS to look at the processor's ACP (Average CPU Power).

Two problems:

  • Focus on CPU power to avoid talking system power, but system power is what one needs to know, in average case to estimate electrical bills.
  • Focus on average CPU power not server maximums that datacenters need to design cooling on (see: http://blogs.sun.com/bmseer/entry/watts_a_matter_with_their.

ACP of a CPU ...hmmm, do you know what a pain it is to just measure a CPU. AMD in their whitepaper , has to isolate the power consumed by the processor and that consumed by the motherboard -- this requires motherboard modifications and special instrumented server platforms!. way to much work to get a marketing message, all we want is server power on a variety of memory configuations and full-speed CPUs and actually running at good datacenter utilizations!

WARNING: Everyone loves to talk performance of high-GHZ CPUs and low-power of low-GHz CPUs, so watch for the confusing marketing and much worse "bait&switch." Also watts per core is useless marketing, it is the watt/perf for a system that counts. Also any vendor trying to sell power-efficiency on high-performance systems should report watt/performance along with their world record performance on that system.

[2] Comments
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Posted at 07:00AM Sep 14, 2007 in Wattage-Power
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AMD and Intel are processor makers. Of course they concentrate on the CPU power use and not the whole system power. That is for the system builders to talk about (Sun and IBM are interesting in that they have their own CPUs as well; Dell and HP are pretty much pure integrators now).

Additionally, CPU power draw is the major power differentiator between systems. For the most part (a little variability here and there, but barely enough to be noticeable, and a few design choices by the builders on numbers of fans, etc), the drives, memory, addins, etc are exactly the same no matter what system you use.

Posted by spp on September 14, 2007 at 01:23 PM PDT #

Spoken like a guy that probably has 4 valves per cylinder in your car, mine has 5 values/cylinder my car is soooooo much better. :) friday-humor

The informed buyer can no make informed decisions without looking at systems. And CPU manufacturers use different memory implementations so because Intel uses FBdimms and AMD uses DDR2 there are big power differences based on CPUs that effect other parts of the system.

Actually Sun has found lots of ways to innovate so you really need to look at the whole picture.

Posted by BM Seer on September 14, 2007 at 01:44 PM PDT #

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