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[nextpage title=”Introduction”]

AMD has recently announced their new dual core CPUs, lauching solutions for both desktop and server markets. The new Athlon 64 with dual core technology has been baptized Athlon 64 X2, while the new dual core Opteron processors keep the same name, but changing their model number system to indicate dual core feature.

With two cores the system works as if two independent CPUs were installed on the system. Thus, only multiprocessing operating systems are capable of taking advantage of dual core CPUs – Windows NT, Windows 2000, Windows XP and all Unix flavors like Linux, FreeBSD, etc. Also, only users that really need a CPU-intensive machine will sense a real performance boost.

The dual core approach from AMD is slight different from Intel. Since in AMD Athlon 64 and Opteron CPUs the north bridge is embbeded in the processor, the CPU itself can control the multiprocessing (this task is done by the north bridge), allowing the two cores to communicate directly without the need of going outside the CPU. On Intel approach, if one core wants to talk to the other core, it has to ask permission to the north bridge, which is located outside the CPU and accessed at a lower speed.

Figure 1: AMD dual core technology overview.

Let’s take a look at Athlon 64 X2 and then on dual core Opteron.

[nextpage title=”Athlon 64 X2″]

As we said, Athlon 64 X2 is the new Athlon 64 with dual core technology. In Figure 2 you take a look at its design, which is the same as the current Athlon 64 processors with the difference of having two cores. This CPU uses the socket 939 platform and all socket 939 motherboards that provide 1.4 V CPU voltage are capable of accepting this new CPU (a BIOS update may be necessary). Since it is based on the socket 939 platform this CPU has DDR Dual Channel memory support.

Figure 2: Athlon 62 X2 main specs.

The announced models were the following.

Model	Frequency	L2 Memory Cache	Pricing*
4800+	2.4 GHz	1 MB + 1 MB	USD 1,001
4600+	2.4 GHz	512 KB + 512 KB	USD 803
4400+	2.2 GHz	1 MB + 1 MB	USD 581
4200+	2.2 GHz	512 KB + 512 KB	USD 537

* Prices for distributors in the USA in 1,000 quantities.

Basically two clock rates and two cache versions.

It is really amazing how expensive is the 4800+ compared to the 4400+ – it costs almost the double –, which are basically the same processor but 200 MHz faster. Also, by this table we can see how AMD is still facing troubles reaching high clock rates. While Intel is over 3.6 GHz range on desktop market, AMD is still stuck at 2.4 GHz.

AMD didn’t provide any performance comparison, but just a comparision between Athlon 64 X2’s technology to Pentium D’s (Pentium D is the commercial name of Pentium 4 with dual core technology), as you see in Figure 3.

Figure 3: Athlon 64 X2 vs. Pentium D.

[nextpage title=”Dual Core Opteron”]

Several dual-core versions of the Opteron processor were released, all using the socket 940 platform. We’ll talk about them all, but first let’s take a look at the dual-core Opteron architecture in Figure 4.

Figure 4: Dual core Opteron architecture.

There are two main difference between Opteron and Athlon 64 processors. First is the memory support. Both have dual channel support, but Opteron requires registered memories, which are targeted to servers. The second main difference is the number of HyperTransport busses the processor has. Athlon 64 has just one HyperTransport bus, while Opteron can have one, two or three busses. Actually Opteron is manufactured with all three HyperTransport busses, but one or two are factory disabled depending on the processor model.

The Opteron 1xx series doesn’t support multi processing and has only one HyperTransport bus. The Opteron 2xx series support multi processing up to two CPUs and has two HyperTransport busses. And the Opteron 8xx series support multi processing up to eight CPUs and has three HyperTransport busses. These extra busses are used to link one CPU to another.

Dual-core solutions were released on the 2xx and 8xx series. As you can see from the table below, dual core models numbering system advance in increments of five versus increments of two on the single core Opterons. The released models are the following.

Model	Frequency	Price *
875	2.2 GHz	USD 2,649
870	2.0 GHz	USD 2,149
865	1.8 GHz	USD 1,514
275	2.2 GHz	USD 1,299
270	2.0 GHz	USD 1,051
265	1.8 GHz	USD 851

* Prices for distributors in the USA in 1,000 quantities.

We can speculate that AMD will also realease dual core models on their Opteron 1xx series.

Performance

AMD says that their new Opteron 275 (2.2 GHz) is 87% faster than Opteron 248 (2.2 GHz) and 69% faster than Opteron 252 (2.6 GHz) on SPECjbb2000 benchmark.

Figure 5: Dual core Opteron performance, according to AMD.