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AMD WHITE PAPER ACP – The Truth About Power Consumption Starts Here Quad-Core AMD Opteron™ processors improve power efficiency with several key technologies: Enhanced AMD PowerNow!™ Technology: For reduced power consumption by the entire processor. Native quad-core technology enables enhanced power management across all four cores. Independent Dynamic Core Technology allows each core to vary its frequency, based on the specific needs of the system. This allows for more precise power management t
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  ACP – The Truth About Power Consumption Starts Here  AMD WHITE PAPER For years, CIOs never had to worry about the cost of power – that financial cost was alwaysburied somewhere in the facilities budget and companies rarely bothered to connect the dotsbetween energy consumption and IT infrastructure. As the world shifted from propriety expensive mainframe technologies to lower cost industry-standard servers, the demands of power on the data center grew and the relationship betweenenergy costs and consumption became clearer, registering a “concern” for the CIO. The lowercost of industry-standard servers offered companies the ability to deploy more servers withintheir data center infrastructure, increasing the compute capabilities and include power andcooling requirements. But still, as long as there was no interruption to the delivery of power orlimits set, CIOs remained unconcerned. Then, industry-standard ultra-dense low cost 1U serversarrived, followed by even denser blade servers. Facilitiescouldn’t supply more power as data center growth hadoutstripped the power capacity. There was no moreroom to expand power capacity, so some businesseshad to stop growing their infrastructure. New ITdeployments were put on hold and businesses startedto be concerned about being uncompetitive based ontheir inability to react to changes in the market or newopportunities. Welcome to the crisis. As companies scrambled to adapt to this new worldwhere power mattered in the data center, getting ahandle on exactly what needed to be done was clear –power consumption needed to be reduced. It’s easyenough to say, but harder to practice because everygeneration of technology was more power-hungry thanthe last. Where do you begin, especially when you maynot have visibility to your power consumption at theplatform level? The simplest way is to take a system-level view of power consumption and address thedifferent components in the platform on a per-devicebasis. Customers will quickly gravitate to the processorbecause this component represents a large percentageof the power consumed in the system. Not manycustomers have the tools to truly measure processorpower consumption, at best they can only measurethe full system.The best way to measure a server’s power consumptionis the power meter, an inexpensive tool that is pluggedinto the wall, and then your device, like a server, can beplugged into the power meter. The meter displays thewattage drawn “at the wall” and allows you to analyzethe power consumption under a variety of differentutilization levels. As you would expect, a server sittingidle draws significantly less power than a server that isunder a full load.It is of little value to measure power consumptionby only looking at the spec sheets for differentcomponents, adding the totals together, because thesegenerally only report the maximum power consumption.This scenario is like the car with a speedometer thattells you the maximum speed is 150MPH – it’s amaximum reading but it doesn’t reflect daily usage.Unfortunately, AMD’s own customer research indicatesthat nearly three out of four customers only useprocessor specification sheets to determine powerlevels. Based on the architectural differences between AMD and competitive processors, like AMD’s integratedmemory controller and AMD’s use of energy-efficientDDR-2 memory, the numbers at the platform level cantell a very different story at the wall compared to thespecification sheets. Quad-Core AMD Opteron ™  processors improve powerefficiency with severalkey technologies: Enhanced AMD PowerNow! ™  Technology: For reduced powerconsumption by the entireprocessor.Native quad-core technologyenables enhanced powermanagement across all four cores. Independent Dynamic CoreTechnology allows each core to varyits frequency, based on the specificneeds of the system. This allows formore precise power managementto reduce data center energyconsumption and thereby reducetotal cost of ownership (TCO). Dual Dynamic Power Management ™ allows each processor to maximizethe power-saving benefits ofEnhanced AMD PowerNow!technology without compromisingperformance. Dual Dynamic PowerManagement can reduce idlepower consumption and allow forper-processor power managementin multi-socket systems to decreasepower consumption. AMD CoolCore ™ Technology: To reduce power consumptionwithin each core AMD CoolCoreTechnology evaluates which partsof the die – the cores, the memory,or both – are needed to supportcurrently running applications. It cancut power to unused transistor areasto reduce power consumption andlower heat generation.   As customers begin to seek more information regardingpower consumption of processors as well as platforms,they are putting pressure on their vendors to delivermore detailed, and most importantly, more accuratepower measurements to help them better determine thetrue power consumption. The days of simply being ableto quote the maximum power from a design standpointare gone forever – customers demand more accuracyin order to help them best plan for their infrastructures.Based on these customer demands, AMD hasdeveloped a new metric to more accurately reflect powerconsumed by the processor as well as the memorycontroller (which is integrated into all AMD Opteron ™  processors) during relevant peak workloads. The new Average CPU Power (ACP) metric is designed to givecustomers a more accurate idea of the power consumedby the processor, allowing customers to more realisticallyforecast their power budget assessments to estimatehow much power might actually be consumed at thewall and more accurately allow them to plan their datacenter power and cooling infrastructure.With AMD Opteron ™ processors, the TDP, or ThermalDesign Power, was used to represent the maximumpower for the processor. Because this was anengineering design specification, it was significantlyeasier for AMD to report to customers. But that didn’thelp customers accurately assess the power requiredfor the processor, because a processor with a 115W TDPmay not break the 70W mark under extremely highworkloads – just like a car with a 150MPH speedometerrarely hits speeds above 90MPH. Some customers wereunnecessarily limiting the amount of growth within therack based on an over-estimated power budget andpotentially sacrificing data center efficiency. Theydemanded more accuracy, and that led AMD to develop ACP, a better way to think about processor powerconsumption.With the introduction of the new Quad-Core AMDOpteron ™ processors, several new power managementenhancements, including AMD CoolCore ™ technology,Dual Dynamic Power Management ™ , and Enhanced AMD PowerNow! ™ technology with IndependentDynamic Core technology all help to reduce powerconsumption of the processor. But to further helpcustomers more accurately model power consumption, ACP was developed to better match customer needs. Breaking Down Processor Power Consumption The new Quad-Core AMD Opteron ™ processors have many power efficiency enhancements toreduce overall power consumption. A new feature called Dual Dynamic Power Management ™  (DDPM) provides the processors with additional power rails which are dedicated to the processorcores, HyperTransport ™ technology links, and memory controller. Separating the power rails ofthe cores allows each of the cores to independently adjust frequency for the given workloadwhile also allowing for voltage changes to the cores. Not only does this technology enableconsiderable power savings at the processor level during non-peak workloads, it also allows AMD to capture the power consumption of the individual sections of the processor during thepower measurements. The ACP values for each power band include the power for the cores,memory controller, and HyperTransport ™ links. 2  AMD White Paper: Power Consumption Integrated DDR2 DRAM MemoryController: low-power memory toreduce power consumption. AMD’sIntegrated Memory Controller worksexclusively with high bandwidth,energy-efficient DDR2 memory.It incorporates Memory RAS forincreased fault tolerance toreduce system downtime andincrease system reliability. DDR2 memory can improve overallTCO by reducing memory powerconsumption almost 8 watts perDIMM compared to fully bufferedDIMM memory technology.  3  AMD White Paper: Power Consumption HOW POWER IS MEASURED To accurately measure in-system power consumptionby the processor, one must isolate the power consumedby the processor from the power consumed by therest of the motherboard. Motherboards contain multiplevoltage regulator modules dedicated to deliveringpower to the individual power rails of the processor,which satisfies this isolation requirement. However, theimplementation of these voltage regulators typicallydoes not allow for direct power measurement withoutmodifications to the motherboard and these regulators.Thus, ACP measurements were taken on speciallyinstrumented internal engineering server platforms.It should be noted that such instrumentation does notchange the power requirements or characteristics ofthe processor itself. This instrumentation allowed forthe direct measurement of all power rails supplyingpower to the processor while the system was running.Measurements were captured multiple times persecond using a high precision digital multimeter. PART SELECTION In general, inherent process variations in semiconductormanufacturing lead to a normal distribution ofmanufacturing output vs. manufacturing targets. As itpertains to power consumption, one can think of thisas processors being slightly colder (lower power) thantarget, on target, and slightly hotter (more power) thantarget. As with any normal distribution, the bulk of thechips are in the “on-target” region. To be conservative,parts used for ACP power measurement were sampledfrom the hotter side of the distribution. WORKLOAD SELECTION  A suite of industry accepted server workloads wasselected as a basis for determining ACP. These includefloating point, integer, java, Web, memory bandwidth,and transactional workloads. Using a suite of serverworkloads that represents the breadth of typical serverapplications allows for a better representation ofenterprise server class workloads used by endcustomers. These workloads were TransactionProcessing Performance Council (TPC-C), SPECcpu2006,SPECjbb2005, and STREAM. The geometric mean ofmeasurements, taken during these workloads, is the ACP. TEST CONDITIONS Given the goal of representing typical power usage inreal world conditions, environmental test conditions werechosen to reflect that aspect (room temp of 70 º F, server’sfan heat sink used, closed case, etc.) The power for thecores, memory controller, and HyperTransport ™ links waslogged multiple times per second throughout the entireduration of the workload tested, and the time-averagedpower consumption for that workload was calculated.The results across the suite of workloads are usedto derive the ACP number. The ACP value for eachprocessor power band is representative of thegeometric mean for the entire suite of benchmarkapplications plus a margin based on AMD historicalmanufacturing experience.So now that you can see how the ACP measurementsare derived and how they are rooted in representativedaily usages, it should be clear that this metric is a bettertool for customers to assess data center power needs.By utilizing ACP, customers can make a more educatedestimate of their true power consumption. TDP,representing the thermal design power, is a rudimentaryindicator of consumption, and may leave customers over-estimating their data center infrastructure needs. In doingthis, customers can potentially waste valuable datacenter space, resulting in un-optimized data centers thatcost companies real dollars through their inefficiency.   AMD White Paper: Power Consumption 43761C ACP – THE NEW STANDARD? The natural question becomes “is this a newindustry standard measurement?” AMD believes themethodology behind ACP should become the newstandard, as it includes both the processor cores andthe memory controller. Today, companies can mask thetrue power consumption by fixating on the processoritself and neglecting to mention the power consumptionof the external memory controller. Datacenter managersshould measure power of the entire platform whilerunning relevant workloads in order to get themost accurate estimate of platform-level powerconsumption. ACP is not a replacement metric forplatform-level engineering thermal and powerspecifications outlined in the AMD thermal and powerdatasheets should be referenced as guidancefor platform-level thermal and power design. SUMMARY Customers are demanding a better methodology fordetermining the power consumption of systems in orderto better plan their data center deployments. For years,TDP was the guideline that was employed, but as moreand more power saving features are integrated intothe processor, the delta between the TDP specificationand the typical CPU power consumption has grownsignificantly. AMD believes that ACP is a better way of thinkingabout typical CPU power that more accurately reflectsthe power consumption levels that customers can seein real life environments.By choosing the “hot” parts and employing a rigoroustesting regimen designed to err on the conservative side, ACP can provide a measurement above what customersexpect to see in daily use but nowhere near asoverstated as TDP has been in the past.  Advanced Micro DevicesOne AMD PlaceSunnyvale, CA 94088-3453www.amd.com Processor ACPSpecificationPower for cores(% of ACP)Power for memorycontroller (% of ACP)Power for HyperTransport ™ links (% of ACP)HyperTransport ™ links (% of ACP)Power at Idle(w/ power management) (% of ACP)Thermal Design PowerSpecifications (TDP) 105W 83%16%1% <   = 25%137W Figure 1: Quad-Core AMD Opteron ™ SE processors (137W theoretical maximum power) Processor ACPSpecificationPower for cores(% of ACP)Power for memorycontroller (% of ACP)Power for HyperTransport ™ links (% of ACP)HyperTransport ™ links (% of ACP)Power at Idle(w/ power management) (% of ACP)Thermal Design PowerSpecifications (TDP) 75W 79%20%2% <   = 25%115W Figure 2: Quad-Core AMD Opteron ™ processors (115W theoretical maximum power) Processor ACPSpecificationPower for cores(% of ACP)Power for memorycontroller (% of ACP)Power for HyperTransport ™ links (% of ACP)HyperTransport ™ links (% of ACP)Power at Idle(w/ power management) (% of ACP)Thermal Design PowerSpecifications (TDP) 55W 74%23%2% <   = 30%79W Figure 3: Quad-Core AMD Opteron ™ HE processors (79W theoretical maximum power) © 2007 Advanced Micro Devices, Inc. All rights reserved. AMD, the AMD Arrow logo, AMD Opteron, AMD PowerNow! and combinations thereof are trademarks of Advanced Micro Devices, Inc. HyperTransport is a licensedtrademark of the HyperTransport Technology Consortium. Other names are for informational purposes only and may be trademarks of their respective owners. The contents of this document are provided in connection with Advanced Micro Devices, Inc. (“AMD”) products. AMD makes no representations or warranties with respect to the accuracy or completeness of the contents of this publication and reserves the right to make changes tospecifications and product descriptions at any time without notice. The information contained herein may be of a preliminary or advance nature and is subject to change without notice. No license, whether express, implied,arising by estoppel or otherwise, to any intellectual property rights is granted by this publication. Except as set forth in AMD’s Standard Terms and Conditions of Sale, AMD assumes no liability whatsoever, and disclaims anyexpress or implied warranty, relating to its products including, but not limited to, the implied warranty of merchantability, fitness for a particular purpose, or infringement of any intellectual property right. AMD’s products are notdesigned, intended, authorized or warranted for use as components in systems intended for surgical implant into the body, or in other applications intended to support or sustain life, or in any other application in which the failureof AMD’s product could create a situation where personal injury, death, or severe property or environmental damage may occur. AMD reserves the right to discontinue or make changes to its products at any time without notice.
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