AMD Turion 64 on the Desktop

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Power at Load

Processor Power Consumption: Load (CPUBurn)
Processor
Clock Speed
Vcore
CPU Power* (DC)
System Power° (AC)
Turion 64 MT-34
1.8 GHz
1.21V
21.9W
58W
Pentium M 770
2.13 GHz
1.300V
23.3W
65W
Turion 64 MT-40
2.2 GHz
1.22V
26.4W
64W
Turion 64 ML-40
2.2 GHz
1.36V
34.7W
73W
Turion 64 ML-44
2.4 GHz
1.36V
37.0W
75W
Athlon 64 3200+
2.2 GHz
1.51V
53.8W
92W
*Note that the CPU power measurements includes losses via the motherboard voltage regulators.
The power drawn by the CPU alone is lower.
° The system power measurement includes losses in AC/DC conversion within the PSU.

Under load, the battle between the Pentium M and the Turion MTs remained too close to call. The Pentium M did improve its standing compared to its performance at idle (without SpeedStep), but this is probably due mostly to the inexplicable drop in core voltage that it saw under load. In any case, neither processor distinguished itself as a clear victor in terms of power consumption. A slight variation in the workload could completely reverse the results, especially when the relative performance of the processors comes into play. A task that the Pentium M is particularly suited to may end up consuming less power simply because the processor doesn't need to work as long to complete it. Ultimately, the differences are probably too small to draw any conclusions ° the margin of error is simply too high.

One slight discrepancy between the Pentium M and the Turion 64s is how well the empirical power measurements match up against the specified TDP for each processor. The Pentium M was operating well below its specified TDP of 27W, while the Turions seemed to be closer to their specified limits. However, with the efficiency losses of the motherboard VRMs taken into account, it is highly unlikely that any of the chips exceeded their specifications. Judging from this, it may be that CPUBurn runs more efficiently on the Pentium M than it does on the Turions ° or perhaps Intel's estimate is more conservative than AMDs.

The biggest differences in power consumption were not between AMD and Intel, but between the different models in AMD's lineup. The differences between the MT/ML Turions and the Athlon 64 finally became visible under load. Just as AMD says, the difference between the MT and ML chips was about 10W. Whether or not this extra 10W is worth the difference in cost is up to you.

The Athlon 64 performed surprisingly well under load. Our sample uses the less efficient Clawhammer core, rated at 89W, but we were pleasantly surprised to see that the combined power demand of this processor and the motherboard's VRM came in at only 54W. That was still much higher than the next highest contender, but it's still better than we expected from a supposedly "hot" Athlon 64.

The ABCs of Desktop Turion 64

If you choose to run a Turion 64 on the desktop with a minimum of fuss, there are a few steps to follow. It's slightly more involved than using a Pentium M for a desktop system, because there are much fewer choices for the latter, which are pre-packaged specifically for Pentium M.

1. Buy a Turion 64 processor. Unlike Pentium Ms, they are not sold in normal retail packaging. Only OEM models are available, mostly from system integrators who use them to build white-box laptops. (Note that retail package Pentium M processors don't include heatsinks, either.)

2. Get a socket 754 board that recognizes E-stepping Athlon 64 processors. Generally any 754 board that has a BIOS dated at least mid-2005 should have this. Check latest BIOS updates and technical information for the motherboard to be sure. (A gotcha: If you have to update the BIOS in order to get E-revision processor recognition, you will need an earlier socket 754 processor to do so. So it's best to use a board that already has the E-stepping processor support.)

If E-stepping A64s are supported, the board will power up with the Turion 64. It may run at the lowest speed by default, but any modern board will let you manually set the clock speed. Just set it to your Turion 64's rated speed and you will be off and running.

3. Get a K8 heatsink/fan that will accommodate the thinner profile of the Turion 64 die, which does not have a heat spreader. Safest are the models that use a captive spring for each of the two mounting bolts. This allows you to apply the pressure slowly and evenly (by going back and forth between the two bolts as you screw it down) so that the base of the heatsink does not tilt under pressure and risk chipping the edge of the CPU die. Most heatsinks apply quite high pressure for a standard A64 (with heat spreader), so when the bolt is fully engaged, there will be plenty of pressure between the Turion 64 and the heatsink. With the Zalman 7000cu heatsink that we used, there were no springs, so how tight to engage the bolts is a judgement call that calls for a bit of common sense. (Note: The 7000cu we used is a very heavy all-copper heatsink which is not ideal for use with a bare-die CPU. Do as we say, not as we do; a lighter 7000alcu is a better choice.)

Other Considerations

The ability to adjust Vcore down manually in the BIOS is a very nice feature to have with the Turion 64, simply because it appears most boards probably feed it too high a voltage, which will cost you a bit of extra power at load. Bring the Vcore down to the 1.35V for ML or to 1.2V for MT ensures lower power consumption. Many of these processors will also run at lower than full rated voltage so that you can get even cooler operation and lower power consumption. For these reasons, manually adjustable Vcore in the BIOS is really great to have.

But if the board doesn't have BIOS Vcore adjustments, it's not critical, as the system will still run much cooler than any equivalent standard desktop system. If you want to lower Vcore lower anyway, it can be done with a couple of Windows utilities ° CrystalCPUID, which we used extensively for our testing, and also RM Clock. These should allow Vcore manipulation with just about any socket 754 desktop board that will run Turion 64.

In our view, Cool'n'Quiet support for the Turion 64 is not that important on the desktop because you're not worrying about battery life, and when run at the correct Vcore, even without CnQ, the power efficiency is already so high. With low CPU power demand, motherboard VRM inefficiencies eat up a big chunk of any additional power savings; the power reduction in our test systems was only 3W to 7W at the wall outlet, depending on processor type and clock speed.

Finally, with the CPU generating so little heat, you will not need much airflow across the CPU heatsink. You can probably use a quiet fan at reduced speed for the lowest possible noise. Choose your other components carefully, as they will impact the overall noise of your system much more than the CPU. This includes the power supply, hard drives and video cards.

CONCLUSIONS

The Pentium M and the Turion 64 are very similar in terms of power consumption. According to the benchmarks from other sites, they are also very similar in terms of performance. Both can easily be used in desktop systems, with a few specialized motherboards for the Pentium M and a huge range of socket 754 boards for the Turion 64. Where they differ dramatically is in price, the Turion being at least $50 or 25% less costly than the equivalent speed Pentium M, and with the top models, some $300 less (50%). That's for the processor alone, but factor in the >$200 price of Pentium M motherboards and the <$70 price of typical socket 754 boards, and you can easily get more than $400 savings by going with a top speed Turion rather than a similar clock Pentium M.

Aside from the Shuttle SD11G5 SFF barebones system, which comes with a quiet, well-designed, integrated CPU cooler, most of the other Pentium M boards have a basic problem: They require the use of a non-standard heatsink and/or HS mounting system, none of which are ideal for quiet cooling. So even after spending big money on a specialized platform and the more costly Pentium M, you still have to fiddle and tweak for a truly quiet setup. For silencers, the wide range of high performance, low noise heatsinks for the socket 754 really tilts the advantage to the Turion.

Why isn't the Turion 64 more widely recognized for desktop use? Many factors are involved, but there are three big ones.

Consumer Awareness: To deliver Pentium M to the desktop, AOpen and DFI had to build the market from scratch by providing the appropriate motherboards ° and the marketing to sell them. Hence, there is consumer awareness of Pentium M as a desktop-viable product.

AMD, on the other hand, has had little interest in selling Turions to desktop users. From what we can gather, they're having enough time keeping up with demand in the mobile sector! So, even though it is perfectly viable to run Turions in desktop machines, nobody has put any marketing dollars behind the concept to make it fly.

Lack of Technical Documentation on the Turion: The relative lack of market awareness is exacerbated by the absence of technical documentation for the Turion from AMD. Without such information, even technically savvy experimenters have to tread slowly and cautiously. "Yes, the Turion works on many 754 boards" ° that statement would be a fair representation of the typical PC enthusiast's knowledge on the subject.

Time / Availability in the Market: Pentium M has been on the market for nearly three years; the Turion perhaps a year. Retail availability for the Pentium M processors has been pretty good for a while. The Turions have been much more difficult to find until quite recently.

Many system integrators have been offering desktop systems based around the Pentium M for some time, usually at a significant price premium over similar performance standard desktop systems. Now, quiet-oriented system integrators could also offer extremely quiet, high performance, and power-efficient Turion-based desktop systems at prices very competitive with equivalent performance Athlon 64 systems, and much cheaper than equivalent Pentium M systems. It's may only be a matter of time before some adventurous retailer begins to offer Turion-based desktops.

Like most products in the tech world, Turion on the desktop will not enjoy that long a run. There are two spoilers on the horizon:

  1. AMD will release a new socket (named S1?) for their dual-core Turion 64. It will not be compatible with any other sockets.
  2. Sockets 754 and 939 will be replaced with a single new socket called AM2, which will become AMD's universal socket/pin configuration for all their desktop CPU models.

Both of these new sockets and processors for them will likely be released by mid-year. They signal the beginning of the end of 754-pin Turion 64s and socket 754 motherboards.

AMD's position on 754 socket processors (Turion 64, Athlon 64 and Sempron) is that as long as there is enough demand from customers, they will keep making them. This is the key to the continued production and availability of socket 754 motherboards as well. Given market realities, it seems safe to say that Turion 64 on the desktop will be doable for at least the rest of 2006. (After all, socket A motherboards are still around in retail, years after cessation of development on processors in this form factor.)

The low power computing scene will undergo many other significant changes this year. Intel will release Conroe, their upcoming low power desktop CPU, and AMD will probably offer reduced power consumption versions of Athlon 64s and X2s. Specialized desktop motherboards to take advantage of Intel's and AMD's dual-core mobile processors may also be developed by the likes of AOpen, DFI and Shuttle. High efficiency computing is coming to the masses sooner or later; the Turions get you there a bit sooner at relatively low cost.

Many thanks for the generous assistance of:

AMD for the Turion 64 samples
AOpen for supplying the i915Ga-HFS motherboard
DFI for supplying the LanParty UT NF3 250GB motherboard
NCIX for supplying the MSI RS482M-IL motherboard
Intel for supplying the M770 sample and the LTS-25 current sensor
Corsair and OCZ for supplying the RAM used in the test systems

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Additional resources and further reading about Turion 64:

The Tech Report - Intel's Pentium M 760 versus AMD's Turion 64 ML-44: Mobile Goliath meets would-be David
Laptop Logic - Clash of the Titans: Dothan vs Turion
Mobility Guru - The Turion 64 Inside Story
AMD - Turion 64 Competitive Comparison
SPCR Forum - Turion supported desktop motherboards
2ch BBS - Turion 64 Motherboard In/Compatibility List
A DIY Report - Building a C'n'Q Home Theater PC with a Turion 64

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Discuss this article in the SPCR Forums.



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