AMD Turion 64 on the Desktop

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Februrary 18, 2006 by Devon Cooke and Mike Chin

This article is one of the most demanding we've tackled at SPCR in quite a while. The idea for the article germinated many months ago, but it's taken all this time to assemble the samples, necessary components and new test gear to bring it to fruition. The testing and writing took several weeks. Turion 64s work on many desktop socket 754 motherboards. What's so hard about that? It's what we thought too, but correctly documenting all the details turned out to be pretty challenging. In the end, it's still not a definitive piece on the subject, but we think it's a good introduction and overview.

- Mike Chin, Editor

Building a silent system is all about managing heat intelligently. With the exception of hard drives, the only sources of noise in a typical PC are fans, and less heat means it's possible to run fewer, slower and quieter fans. Advances in heatsinks and power supplies have made it easier to just slap together a few parts to make a system that is reasonably quiet, but the basic problem, heat output, still remains. Even the best heatsinks on the market struggle to cool the hottest processors, and no power supply is immune from the efficiency losses ° and increased heat ° caused by sustained high output.

So, how do you go about reducing heat output? The amount of heat in a system is directly proportionate to the amount of power it consumes, so reducing heat means cutting down on power consumption. A number of methods for doing so have become popular at SPCR, including

  • Undervolting and underclocking: Slower, low voltage chips consume less power
  • Deliberately choosing low-end parts, as they are often slower and lower voltage than the latest and greatest
  • Choosing more efficient parts, with high performance to watt ratios
  • Using parts designed for the laptops (such as HDDs and CPUs), which consume minimal power to conserve battery life

Hardware manufacturers have also recognized the importance of reducing power; high efficiency power supplies are now de rigeur, and Intel and AMD have added performance-per-watt as one of their competitive benchmarks ° still a big step below the alter of high performance, but at least the parameter is now in the cathedral. Nowhere is this more apparent than in the mobile processor market, where low power consumption translates into long battery life as well as low noise. Intel's Pentium M processor (part of the "Centrino" brand) is probably better known than AMD's Turion 64, but both have a lot to offer in terms of performance per watt.

It's widely known that the Pentium M can be used to power a desktop system thanks to a growing number of motherboards and Small Form Factor systems designed specifically for it. The Pentium M uses a pin array that looks like it should fit in a standard socket 478, but its configuration is different and it requires a socket 479 board to work. Bringing Pentium M to the desktop required the interest and sustained effort of companies such as AOpen and DFI, who did not have official Intel support. Intel's view for a long time was that the Pentium M and socket 479 are part of the laptop-specific Centrino platform and should be supported by the mobile division.

There was early interest in Pentium M for the desktop right here at SPCR. The first reference in the forums appeared back as early as mid-2003 when forum member Beyonder wrote: "I think I'd chew off my arm for a Centrino MB and processor solution for the desktop segment at the moment...." Since then, we've helped popularize the Pentium M for desktop by reviewing no fewer than five products designed specifically for this processor:

Not many people realize that the Turion 64 can also be used in this way. In fact, it doesn't even require a special motherboard ° many Socket 754 boards that support desktop processors can also run Turions. Ironically, this compatibility is one of the reasons that Turion 64 for the desktop has not been as popular a concept: There are no special products for this application, and no special marketing efforts by any interested companies to promote the product as there have been for the Pentium M. Hence, there isn't much awareness about the concept of Turion 64 on the desktop.

TURION 64 PERFORMANCE

Another reason why more people haven't turned to the Turion 64 is because not much is known about it. AMD has done a good job of selling the Turion 64 as a notebook processor, so people tend to assume that it is less powerful and less interesting than the top-of-the-line Athlon 64 and X2 processors. Sure, it may be efficient, but why trade performance for efficiency?

Here's an open secret: The Turion 64 is based on the same AMD64 architecture that powers AMD's desktop and server processors. In terms of performance, the Turion 64 should perform identically to an Athlon 64 of the same specifications. So how does AMD justify saying that the Turion 64 is "designed from the ground up"? The key is in the silicon. Although the processor logic is the same, the underlying technology is not. Turion 64 chips are built from low-voltage transistors that have less electrical leakage, and the layout of the chip has been optimized for low power, not high speed.

This does not mean that the Turion 64 will perform slower. The effect of the optimizations is to reduce the maximum potential clock speed that the Turion 64 can support; clock for clock, there should be no difference. The effect of the slower transistors can be seen in the range of clock speeds for each processor: 1.6 ~ 2.4 GHz for Turion 64 chips, and 1.8 ~ 2.8 GHz for Athlon 64 and Athlon 64 FX chips. In theory, the regular Athlon 64 chips should be better overclockers than the Turion 64 chips.

Of course, there are other factors that affect performance, like socket choice. Turions are available only for Socket 754, which means they cannot take advantage of dual channel memory, which is the domain of Socket 939. Another factor is dual core. AMD's top processors all feature two cores, but this feature has yet to show up in their Turion 64 lineup. When it does, a change in socket type will render the dual core Turions incompatible with desktop equipment.

TURION 64's ATHLON 64 EQUIVALENTS
Turion 64 Model & TDP
Athlon 64 Equivalent &TDP
Clock Speed
L2 Cache
Socket Type
HyperTransport Speed
ML-44 (35W)
Clawhammer 3700+ (89W)
2.4 GHz
1 MB
S754
1.6 GHz
MT-40 (25W)
Clawhammer 3400+ (89W)
2.2 GHz
1 MB
S754
1.6 GHz
MT-37 (25W)
Clawhammer 3200+ (89W)
2.0 GHz
1 MB
S754
1.6 GHz
MT-32 (25W)
Clawhammer 2800+ (89W)
1.8 GHz
512 KB
S754
1.6 GHz

The table above should give you a good idea of what the Turion 64 chips are capable of, performance-wise. We've picked the closest matches we could find between the two processor familes. The Turions should perform a little faster and run considerably cooler, since they are based on a newer revision of the AMD64 architecture (E5) than the Clawhammer chips (C0, CG). The equivalent desktop core (E6) is not widely available for Socket 754; the ones that are available sport 512KB cache rather than the 1MB of most of the Turion 64s.

So much for the AMD comparison. But, the Turion 64 is not meant to compete against the Athlon 64. The real question is how it stacks up against Intel's Pentium M. Extensive performance testing is not SPCR's raison d'°tre, but the short answer is it's too close to call. The Tech Report and Laptop Logic have both done detailed performance comparisons of the two processors. Our study of such reviews and our own extensive experience with Turion 64 and Pentium M desktop system has convinced us that there is no compelling performance reason to choose between the Pentium M and the Turion 64. They are both powerful, modern processors that provide speed performance; when you factor in their power efficiency, their performance is staggering ° sort of like a 60 mpg hybrid also capable of 0 to 60 mph in 6 seconds.



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