AMD: the triple core is now official

Just a month after revealing the name, clock speed and thermal design power (TDP) of its triple core processors, AMD has introduced its new quad core Phenom with B3 stepping and the processor is already available. While the Phenom X3 CPUs still do not show up in AMD's official price list, the processors are supposed to sell for between $145 (Phenom X3 8450) and $195 (Phenom X3 8750) – that is, if you order a thousand of them. This positions the Phenom X3 8750 in the $30 gap between the cheapest quad and the most expensive dual core processor. But Intel's most recent price drop may put AMD prices under even more pressure. The price of the cheapest Core 2 Quad (Q6600) has dropped 16% to $224.

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Amdcompare.com confirms a 95 watt nominal TDP for all three triple core models. The combination of this quite high value and the modest clock speeds of 2.12 to 2.4 GHz indicate that, with the triple core CPUs, AMD is attempting to increase the yield rate of Fab 36 in Dresden – currently the only plant producing 65nm K10 processors; all of the Phenoms have the same die. As the final step of the manufacturing process, AMD uses laser fuses to specify how many cores the CPUs are allowed to use and at what clock speed they should run, as well as the core voltage that the voltage transformer on the motherboard has to deliver. The number of chips AMD can sell depends not least of all on how many CPUs at what core voltage attain what clock speeds. The better a chip is, the higher the clock speed it can attain at a low core voltage. Chips that push the limits of manufacturing tolerances often need higher voltages for the same clock speed. The higher the core voltage is, the more current there is heating each individual core. If you deactivate one of four cores, the remaining cores can divide up its power amongst themselves to achieve higher clock speeds without the TDP of the chip exceeding the specified values. This is how the three cores in the Phenom X3 8450, for instance, divide up 95 watts TDP to achieve a clock speed of 2.1 GHz. The four cores of the Phenom X4 9550 attain a speed of 2.2 GHz with the same thermal budget.

At 95 watts, the X3 Phenoms are well suited to motherboards with the AMD 780G chipset, which cause problems for performance hungry quad core CPUs. The same goes for the Gigabyte GA-MA78GM-S2H, whose capacitors got dangerously hot when a 125 W CPU was used in a c't test, and which excludes the Phenom X4 9850 from its compatible CPU list.

(trk)