Athlon 64 X2 is an Athlon 64 with dual-core technology, i.e. it has two complete CPUs packed together. Read our tutorial Dual Core AMD Processors to learn more about this technology. As mentioned, AMD has changed the name of this CPU to Athlon X2 and, a little bit later, to Athlon X2 Dual Core, so Athlon 64 X2, Athlon X2 and Athlon X2 Dual Core are the same CPU.

Athlon X2 processors can use socket 939, AM2 or AM2+. On socket 939 models you may need to perform a BIOS upgrade if your motherboard was released before they reached the market in order to support them.

Like single-core Athlon 64 processors, Athlon X2 CPUs are identified by a four-digit model number (e.g. Athlon 64 4000+, Athlon X2 6000+ and so on). This numbering system allows you to compare the performance of CPUs from the same family. Inside the same family, the higher the number, the faster the CPU is. For example, Athlon 64 4000+ is faster than Athlon 64 3800+, which in turn is faster than Athlon 64 3400+.

We only can use this numbering system to compare processors that belong to the same family. We cannot say that Athlon 4000+ is faster than Athlon X2 3800+ just because its model number is higher. These two processors belong to two different families and thus we can’t compare apples to bananas.

AMD is now adopting a new numbering system for their processors. This new system is more complicated than the previous one and will only be adopted by new processors, i.e. processors that were already launched with the old numbering system won’t have their model number replaced, keeping the old naming.

This new numbering system uses a five-character format: XX-####, where XX are letters and #### are numbers. The two letters indicate the processor class, with the second letter indicating the CPU thermal dissipation (TDP). The first number after the dash indicates the processor series and informs the CPU features. The three last numbers indicate the position of the CPU within its series and class. The higher this number, the more features the CPU has – usually indicating a higher performance within its class and series.

Athlon X2 Dual Core is the first processor to adopt the new numbering system. Just to exemplify how this new numbering system works, Athlon X2 Dual Core BE-2350 belongs to “BE” class (the letter “E” indicating that this CPU dissipates 45 W), “2xxx” series and its number within this series and class is “350”.

Athlon 64 X2 main features include:

• Two processing cores.
• 64 KB instruction L1 memory cache and 64 KB data L1 memory cache for each core.
• 512 KB or 1 MB L2 memory cache for each core.
• 2 MB L3 cache on AM2+ models.
• HyperTransport (HT) bus running at 1 GHz (4 GB/s) on 939 and AM2 models. This clock may also be referred as “2,000 MHz”. On AM2+ models this bus runs at 1.8 GHz (7.2 GB/s). This clock may also be referred as "3.6 GHz".
• Socket 939, AM2 or AM2+. Socket 939 models accept only DDR memories while socket AM2 and AM2+ models accept only DDR2 memories.
• Dual channel configuration on all models (you need to install two or an even number of memory modules to use this feature).
• SSE3 instruction set on all models.
• SSE4a instruction set on AM2+ models.

On the table below we list all Athlon 64 X2 released to date. TDP means Thermal Design Power and indicates the thermal dissipation of the CPU, i.e. the CPU cooler must be capable of dissipating at least this amount of heat.