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LOSTCIRCUITS

SHORTCUTS:
Energy-Efficiency
CPU vs. System Power
CPU Specs and Numbers
Test Setup, Benchmark Overview
Idle Power, Prime95
3D Rendering Power
Cinebench 2003
Memory Subsystem
Access Latencies
3DMark '05 and Gaming Power
FarCry, Call of Duty2
F.E.A.R., Prey
DOOM3
Final Thoughts

Give Us Some Feedback on this Review

 Low Power and Energy-Efficient CPUs from Intel and AMD
Core2 Duo E6300 vs. X2-3800+ (ADD) and X2-4600+ (ADO)
(Review by MS, August 20, 2006)

Processor vs. System Power

On the last page, we were talking about the introduction of low energy processors into the market and the new metrics of instructions per [W]. In real life, the entire situation is a bit more complex than just measuring CPU power. On the one side, there are the low energy processors, on the other side is the increasingly complex and power-hungry memory and graphics subsystem. On the memory front, things are still halfway under control but let’s look back to a Platform conference in 2001 and a quote from Levi Murray at AMD: “If the system memory only consumes less than 10% of the power of a CPU, then a 30% power reduction of eDDR2 compared to a non-cached architecture does not really seem to make much of a difference in the overall picture”. This has certainly changed, system memory densities have increased to 1-2 GB average with a power consumption under load currently peaking in the 20-30 W range.

If memory and CPU power consumption are on the way to reach parity, the graphics subsystem has shattered any chains known to power consumption a long time ago. Quad SLI configurations with up to 400W power consumption are the current main offenders but this is just the beginning and it won’t be too long until we see 600W being gobbled up by dual or quad-GPU solutions. At the same time, the graphics subsystem is still the major bottleneck in overall gaming performance so why should we even care about energy-efficient CPUs?

The answer is the same as that from 6 years ago: “you have to start somewhere”. Moreover, the mobile market is more energy-aware than ever and after all, this very mobile market is the fastest growing segment in the entire computer industry. Not to mention the fact that where there is a leader, there will be followers – in other words, if there are finally some low power CPUs, chances are that the same tricks will be implemented in the GPU-world as well on a way to a more energy-efficient, cooler running computing. In this respect, the new axis alliance between AMD and ATI is of particular interest as well as any sharing of process technology between Intel and nVidia.

We are not there yet, though and for the time being, we are looking at the current jewels from both AMD and Intel. In the case of the Intel Core2 Duo E6300 we need to stress the disclaimer that the “half-cache” version is not a true half-cache with a 2 MB SRAM, rather, ½ of the addresses have been disabled. This idiosyncrasy of the test sample may have some averse effects on the overall power consumption, especially under low load, in that for example some aspects of the dynamic clock gating may not work as efficiently as in a 4MB cache version. In other words, keep in mind that what we were using here is a preproduction engineering sample that may not have been as optimized for power consumption as the final production run.

Athlon64 X2-3800+
(ADA3800DAA5CD)
Core2 Duo E6300
(HH80557PH0362M)

next page: => CPU Numbers and Specs =>

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