AMD Turion 64 on the Desktop

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Although there have been several comparisons between the performance of the Turion 64 and the Pentium M, power consumption has not been closely looked at... at least not closely enough for our standards. So, we set out to find out exactly how much power the Turion requires. We know it's not much, but how much is not much?

First we had to get our hands on some Turions. AMD generously supplied three Turions: The most power hungry model (ML-44), and two equivalently clocked chips with different TDPs (ML-40 and MT-40). Two of these (the "ML" models) are rated for 35W, the other two ("MT") for 25W. We also purchased a relatively low powered model (MT-34) used from an SPCR forum member.The four Turions would go head to head against each other, a Pentium M 770 (2.13 GHz), and a standard Athlon 64-3200+.

Our most and least power hungry Turion chips, side by side.

Two 2.2 GHz chips, two different TDPs.

With true excitement (and a little trepidation) we plugged one of the Turion 64s into a socket 754 motherboard that we had on hand, an EPoX EP-8KDA3+, carefully installed a Zalman 7000 HSF (more on that later), and pressed the power button: Alas, the board wouldn't post. We tried again after swapping out the processor with an Athlon 64 and updating the board with the latest BIOS, but again, it would not show any sign of life with the Turion.

EPoX EP-8KDA3+: Great board, but no Turion 64 support.

Undeterred, we turned to the web to find a board that would work, and decided that a DFI LanParty UT NF3 250GB might be the way to go. It is an older board based on the older nForce3 chipset, but many people reported success using it with the Turion 64. It was also on a list of socket 754 motherboards that people have (and haven't) succeeded in using with Turion 64, created by a Japanese enthusiast. The caveat on is that the 40 or so boards on the "works" list are not guaranteed to have full functionality with the Turion 64.

DFI LANParty UT NF3 250GB: Turion 64 recognition, but no CnQ.

Two days later, the DFI board showed up, and we tried again. Success! The Turion 64 was recognized correctly, Windows was duly installed, and we began to take some basic measurements. Then we noticed something strange. No matter how hard we pushed the CPU, the clock speed never went above 800 MHz. Obviously, something wasn't right.

A close examination of the BIOS revealed that the chip could be manually set to the correct maximum clock speed and voltage, but no matter what we did, we couldn't enable Cool'n'Quiet. A conversation with Damon Muzny at AMD revealed why: Cool'n'Quiet for Athlon 64 and PowerNow! for the Turion 64 are similar, but not identical. The difference is in the default power state of the processors: The Turion defaults to the lowest clock frequency and voltage, and with PowerNow!, the clock jumps up when needed. The Athlon 64 defaults to the highest clock frequency with Cool'n'Quiet dropping down the speed and voltage when the processor is idling. Naturally, CnQ and PN! have differences in their code, which is why the default clock speed of the Turion 64 was 800 MHz on this DFI board.

The lack of CnQ functionality in the DFI board was a bit disappointing, but it doesn't mean the board cannot be used. Since the BIOS allows for great flexibility, the Turion 64s could be run at many different settings. It could easily be set to the stock voltage and speed, and left at that. However, such a configuration would not allow CnQ to be used, which we really wanted to experiment with, so our search continued.

The next motherboard we tried was an MSI RS482M-IL. This ATI Radeon XPRESS 200 chipset board recognized the Turion 64 and treated it as if it was an Athlon 64, with full CnQ functionality. Considering the differences between the Turion and Athlon, and between PowerNow! and CnQ, we don't really know why and how CnQ works on this board, but it's great that it works!

MSI RS482M-IL: The only board we've found (so far) that supports Cool'n'Quiet on Turion 64.

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