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Kuma vs. Brisbane

To test the new dual-core processors on Stars (K10) microarchitecture AMD provided us with an AMD Athlon X2 7750 sample – the top model in the lineup. The CPU looks exactly like other Socket AM2+ processors. Only the marking gives away its real origin:

First of all, you can notice that although the previous generation dual-core CPUs were marked with “AMD Athlon 64 X2” engraved on the heat-spreader, this processor only has “AMD Athlon” left. Secondly, the processors with Stars (K10) microarchitecture also have a different line in the marking that states the new model number, 2MB L3 cache and the use of the new die.

By the way, since the new Kuma processors use 7000 series numbers, AMD ends up with a very fine naming system for the new generation CPUs. 9000 series is used for quad-core processors, 8000 series – for triple-core ones, and 7000 series – for dual-core ones. However, the upcoming launch of the new Phenom II X4 family, will ruin this logical harmony.

But let’s get back to our today’s hero, AMD Athlon X2 7750. It works at 2.7GHz nominal frequency, which is reported by the diagnostic utilities:

Screenshots also reveal other information about the features of the new AMD Athlon X2 7750. The total CPU L2 cache is 1MB (512KB per core) and shared L3 cache is 2MB big - the same as by the Phenom CPUs. I have to remind you that CPUs on Stars (K10) microarchitecture have their L3 cache memory and memory controller working at their own frequency. In this case it is set at 2.0GHz, like by the fastest Phenom X4 processors.

AMD Athlon X2 7750 CPU is the top model among the new dual-core processors. We specifically stress this fact for you, because the clock speeds of the previous generation Athlon X2 processors on Brisbane core range from 2.7 to 3.1GHz. In other words, the new Kuma processors are inferior to their predecessors in clock frequency, however, it doesn’t prevent AMD from positioning them one step above Brisbane. This is possible due to a number of indisputable advantages that you can see by simply comparing the processor families side by side:

In fact, there are quite a few differences. The new processors support SSE4A instructions, faster HyperTransport bus and faster DDR2-1066 SDRAM. But at first glance it seems that the most important advantage of Kuma over Brisbane that can affect the actual performance is L3 cache-memory. Speaking about the advantages of the new processors, we shouldn’t forget that Stars (K10) microarchitecture boasts a number of improvements hidden deep in computational cores. Due to these improvements the CPU can process more instructions per cycle.

To back up these statements we compared the performance of the new AMD Athlon X2 7750 processor against the previous generation Athlon X2 5200 working at the same 2.7GHz frequency:

As you can see, K10 microarchitecture gives Kuma processors a serious advantage over the predecessors working at the same clock speed. This advantage makes about 15%. In some applications that work a lot with large L3 cache memory of the new CPUs, the performance difference reaches 20-25%. So, not very high clock frequencies of the new Athlon X2 7000 processors shouldn’t discourage you at all: other strengths of the microarchitecture make up for the not very high clock speed.

Nevertheless, looks like we cannot really state that the performance of the dual-core AMD processors has got to a new qualitative level. However, only fully-fledged test session will be able to confirm or deny this assumption. Therefore, let’s get down to it right now.

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