Platform Trends: AMD Hits a Triple with the Phenom X3

In baseball, a triple is the most difficult hit, and players are warned not to be tagged for the first or last out at third base. So it's appropriate that, in its extra-innings contest with Intel, AMD has launched a new line of triple-core desktop processors -- the Class AA cousins of its big-league, quad-core Phenom CPUs, so to speak.

Due to architectural differences, AMD's new Phenom X3 chips have the triple-core market all to themselves, wedged between Intel's incredibly popular Core 2 Duo and Quad. AMD is playing up the "three cores for the price of two" angle quite nicely, promoting the X3's better multithreading performance compared to the lower-priced Athlon 64 X2.

Rounding Second and On To Third

The newcomers include the Phenom X3 8450 (2.1GHz), 8650 (2.3GHz), and 8750 (2.4GHz) processors. The first thing you notice is that AMD skipped a hypothetical 2.2GHz model 8550. The second is that the new CPUs' relatively low clock speeds are something of a surprise, as it was assumed that a triple-core could be clocked higher than a quad -- or, at least, that the X3 line would match the 2.5GHz Phenom X4 9850.

Apart from model numbers beginning with 8 versus the X4 series' 9, the tri-cores share the same base numerical ratings as their counterparts, as well as the corrected B3 core revision indicated by a 50 suffix as in 8450 or 8750. The base architecture is consistent with a standard Phenom X4, but with one of its cores disabled. This reduces Level 1 and Level 2 cache by one-quarter, while the shared L3 remains at a full 2MB. Due to the lower number of cores and the resultant drop in voltage, the X3 8750 is able to run at the same 2.4GHz clock speed as the Phenom X4 9750, but drops thermal design power from 120 watts to 95.

The lower power consumption and heat are two prime advantages of the Phenom X3, and give AMD a CPU seemingly tailor-made for its vaunted 780G integrated-graphics chipset platform. The Phenom X4 is certainly affordable enough, but at 125 watts at the top end (or 140 watts for the upcoming X4 9950), the power specs simply don't match what is required in an entry-level system. Even the 95 watts of the 2.4GHz X3 might be too high, but that's a maximum rating, and the 2.1GHz X3 8450 should be comfortably under that.

Phenom X3 pricing ranges from $145 for the low-end model 8450 to $195 for the flagship X3 8750, which brings up a few question marks. Purely from a cost perspective, the $195 price tag of the 2.4GHz X3 8750 is the same as the 2.2GHz model X4 9550, which will be enough dfor some to go the quad-core route. Even at 2.4GHz, it's only an extra $20 to the Phenom X4 9750 and then another $20 for the 2.5GHz Phenom X4 9850 Black Edition.

Its lower power and thermal requirements will be the main selling points of the Phenom X3, and these are no small concerns, especially with summer heat approaching. The power consumption at idle represents a slight improvement over the Phenom X4, but once you place a CPU load on the X3, its lack of a fourth core pays serious dividends and knocks the consumption numbers down by a proportionate amount. The tri-core does represent an intriguing choice for buyers scared off by the high power consumption of the top X4 models, especially those looking to upgrade existing AM2 systems.

Turning Lemons To Lemonade?

One financial benefit of the Phenom X3 triple-core is that it makes better use of available quad-core processing, as any Phenom X4 with one core that doesn't make the grade can be sold as an X3 rather than thrown away. You can't really do that with a dual-core, as that means a lot of extra silicon just sitting around, rather than achieving the inherent cost and thermal benefits of a true dual-core architecture.

But gambling on low yields works only so long, and if demand increases while production efficiency rises, AMD will likely be forced to lobotomize perfectly sound Phenom X4s. That will cost money, and is potentially another reason why AMD is keeping X3 prices within close proximity of the X4. After all, the company can't just shrug and say, "Yes, we have no triple-cores today" when powerful OEMs demand them.

That is why many feel that the Phenom X3 is a stopgap product that may well be phased out once AMD is able to manage 45-nanometer-process production for its dual- and quad-core processors. It's also obvious that until AMD can join Intel at 45nm, releasing a dual-core Phenom would not be a wise decision, and the triple core is its temporary replacement.

Current benchmarks show the Phenom X3 and X4 falling just behind the highest-clocked Athlon 64 X2 models in single-threaded tests such as games. The newer CPUs are only redeemed by higher multithreading speed -- an advantage a dual-core Phenom would not enjoy.

Stars on 45

From talking with AMD reps and reading between the lines, it is obvious that a 45-nanometer Phenom is viewed as a must-have for the company's future viability. AMD has found itself a generation behind Intel where process technology is concerned, and is currently trying to stave off 45-nanometer-process Core 2 processors with lower-clocked, 65-nanometer Phenoms. That's a hard road to hoe, but if AMD ever catches up, Intel could be in for a real fight.

Unfortunately, plans to implement volume shipments of 45-nanometer Phenom processors by mid-2008 have slid to the end of the year. We'll still see 45nm parts trickling in earlier than that, but likely using the more profitable trickle-up formula, where the best-selling models are the first to see the improved technology. Until then, AMD will rely on the Phenom X3 and X4 to hold the fort.

Intel does not have a triple-core, and with the current Core 2 architecture, it's doubtful it could even be achieved. So in the face of a potential Phenom X3 challenge, naturally, the silicon giant has responded in the only way it really can -- cutting prices on some popular Core 2 processors. This is another challenge AMD must face, and with Intel covering both second base and home plate, we'll have to wait and see whether the Phenom architecture is safe on third.