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Frontpage Slideshow | Copyright © 2006-2010 orks, a business unit of Nuevvo Webware Ltd.
Wednesday, 15 July 2009 13:28

AMD Phenom II Energy Efficient CPUs tested

Written by Eliot Kucharik
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Review: Efficiency pays off


The new Phenom II CPUs are quite a success for AMD. While the 955 Black Edition is the most famous CPUs on our price search engine with the Q9550 close behind, the only concern some users and we have is the high energy consumption. Meanwhile AMD has released two energy efficient CPUs to counter Intel on real world power consumption. Today we will check out if AMD succeed in making truly power efficient processors once again. 

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Both CPUs, the 705e and 905e are the same as their "bigger" brothers. Both are clocked with 2.5GHz, have 3x respectively 4x 256kB L2 cache and 6MB shared L3 cache. The only major difference is the VCore. While the triple-core comes with 1.175V the quad-core manages 1.15V. This means AMD has matched the VCores used on Intel CPUs.   

The TDP is now rated 65W, which is lower compared to Intel. But AMD does always use much more power and Intels TDP ratings are way too high for E- and Q-series.


Testbed:

Motherboard:
MSI 790GX-GD70 (provided by MSI)
AMD 790GX/SB750
MSI DKA790GX (provided by MSI)
AMD 790GX/SB750
ECS Elitegroup A790GXM-AD3 (provided by Elitegroup)

AMD 790GX/SB750
Intel DX58SO "Smackover" (provided by Intel)
Intel X58/iCH10R

CPU:
AMD Phenom II 705e (provided by AMD)
AMD Phenom II 905e (provided by AMD)
AMD Phenom II 720 Black Edition (provided by AMD)
AMD Phenom II 810 (provided by AMD)
AMD Phenom II 955 Black Edition (provided by AMD)
Intel E7200 (provided by K&M Elektronik)
Intel E8400 (provided by Intel)
Intel Q9450 (provided by Intel)
Intel QX9650  (provided by Intel)
Intel Core i7 920  (provided by Intel)
Intel Core i7 975XE  (provided by Intel)


CPU-Cooler:
Scythe Kabuto (provided by Scythe-Europe) for AMD and Intel E/Q
Thermalright Ultra 120 eXtreme 1366 (provided by Thermalright) for Intel i7

Memory:
Kingston 2GB Kit PC2-9600U KHX1200D2K2/2G (provided by Kingston)
1066MHz CL5-5-5-15 CR2T at 1.90V for AMD DDR2
Qimonda 3GB Kit PC3-8500U (provided by Qimonda)
1066MHz CL7-7-7-20 CR1T at 1.55V for Intel i7
Kingston 3GB Kit PC3-10600U KHX1600D3K3/2GX (provided by Kingston)
1333MHz CL7-7-7-20 CR1T at 1.50V for AMD DDR3

Graphics Card:
MSI R4850-2D1G-OC (provided by MSI)

Power supply:
PC Power & Cooling Silencer 500W (provided by PC Power & Cooling)

Hard disk:
Western Digital WD4000KD (provided by Ditech)

Case fans:
SilenX iXtrema Pro 14dB(A) (provided by PC-Cooling.at)
Scythe DFS122512LS

Case:
Cooler Master Stacker 831 Lite (provided by Cooler Master)

OS:
Since we are still not fans of Vista, all tests are performed with XP SP3. As 64-bit software is still not very common, we stick with the 32-bit version.







Here the first CPU-Z screenshots of the 705e and 905e. If you will use this CPUs without tampering anything on your mainboard it will manage to keep temperatures below 30°C in idle-mode. So, not only do the new CPUs use less power, but they also let you use them without the need for high-end coolers to keep the temperatures in check.

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For overclocking you need to increase the virtual FSB. Of course we use high-end boards which can easily exceed 300MHz. The most interesting part was to check how much voltage is needed to match the bigger brothers 720 and 955BE. Our Triple-Core needs no change from its 1.175V VCore to work stable with 2.8GHz, while the 905e needs 1.225V to run at 3.2GHz. The only downside of this locked CPUs is the increased voltage in idle-mode when overclocked, as you can see with the 905e which exceeds 1.000V. 

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Of course we checked the limits of both CPUs and both reached stable 3.50GHz. While this may not sound that much, in perspective this is a huge 1GHz increase with standard air-cooling and very moderate voltages. To do a good overclock you should use good modules, the AMD limit is about 1600MHz. The 705e managed to run stable with 1.350VCore while the 905e needs 1.400VCore. Please note, each CPU is different, but we are confident the frequency can be reach on any of this CPUs while VCore may vary.
 
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With the amazing MSI board, we could run power efficient Cool'n'Quiet while still overclocking.

For HTPC use with very small cases also under-voltage is an interesting point. The triple-core runs stable with only 1.000V, while our quad-core needs  1.050V, a neat effect is the lowering of the idle-power as well, at least on the 705e, while the 905e was still above 1V, because the under-voltaging did not allow for 0.01V steps, which will hopefully fixed soon.
 
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Our benchmarks are quite self-explanatory. Beside the usual benchmarks we included the Far Cry 2 Bench, which should show only the benefit of a faster CPU. While the AMD triple-cores runs against the E8x00 series, the quad-cores are not as fast as Intel's, but they are a bit cheaper.

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3DMark 2003 run at 1600x1200, 3DMark 2006 used defaults. As you can see, more CPU muscle doesn't really help. AMD has positioned the triple-cores against Intel's dual-core offerings, and as you can see in FarCry2 the third core does help to keep Intel in check, even when this game is clearly not optimized for AMD.


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With a reduced TDP rating of 65W for the Phenom IIs is very neat, triple-cores do not shine here, just 20W shy of the 720 is not that great. The 905e does better, about 40W less is much more competitive and is closing the gap compared to Intel. You can see this especially in the CB efficiency charts.  Because we saw some inconsistencies we did all power testings again, two cores loaded always with 3DMark and one or two cores running lamemt. The 905e now can match Intel's Q9 offerings even running slower clock by clock.

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Conclusion

Both CPUs are priced quite equally to the top of the AMD range. While both are not Black Editions, both CPUs can match the clocks of the top CPUs easily. The nice advantage for both CPUs is the reduced energy consumption, so now you can be "green" and an AMD "fan-boy". Also the lower VCore decreases the temperature, so monster-coolers are not necessary but good cooling is always welcome. 

The Triple-Core AMDs are placed against Intel Dual-Core offerings and they can beat them easily. Also the E8 series is way to expensive, because for the same money you can buy Q8 Quad-Cores and Q9s are only slightly more expensive.

In an upcoming article we will check out how standard CPUs react to undervoltaging, as requested by some of our readers. Please note that some low-end boards don't allow undervoltaging.

The 705e is available for about €103 or £ or $124. With the right board you may also unlock the fourth core, something our boards don't allow. Of course the quad-core is more expensive and does sell for about €164 or £139 or $190. So for the more enthusiast user we can recommend the new AMD CPUs and with graphics-cards priced low too, you can build a gaming-machine easily. While the 705e does not shine that much, the 905e does deserve our Recommended Award.


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Last modified on Wednesday, 15 July 2009 13:39
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