Closer Look: CPU

During the work on the new processor, AMD took the successful Athlon architecture as a basis. That is why the newly designed CPU has very much in common with the predecessor. Without going into details, I will list here the major differences between the ClawHammer core of the upcoming Athlon 64 processor and the contemporary Athlon XP.

• Athlon 64 features better branch prediction algorithms and bigger TLB, which will make Athlon 64 run faster than Athlon XP working at the same clock frequency.
• Integer pipeline of Athlon 64 is a little longer, which allows reaching higher clock frequencies. The integer pipeline of this processor has 12 stages altogether, while the FPU – 17 stages, against 10 and 17 stages respectively by Athlon XP.
• Athlon 64 supports SSE2 instructions. This way this processor will support all existing extensions of x86 instructions set, which will allow it to work faster with applications optimized for Intel Pentium 4 processors.
• Athlon 64 feature a built-in DDR SDRAM controller, so that it can communicate with the memory directly thus reducing the latencies on data requests.
• The CPU and the South Bridge will be connected with the HyperTransport bus with up to 3.2GB/sec bandwidth in each direction.
• Athlon 64 processor supports x86-64 technology, which allows it to work in special 64bit applications.

It’s also an Athlon, but a different one.

Well, please meet the CPU, which we managed to get:

AMD Athlon 64 2800+

As we see, our CPU is marked according to the rating, i.e. as 2800+. The production date in the next line of the marking indicates the beginning of this year. Athlon 64 processor with this rating is most likely to become the slowest model in the new processor family, when it is finally launched.

As we see, AMD is not going to give up the idea of marking CPUs with the rating instead of writing their actual core frequency. Well, let’s find out what hides behind this marking.

Many of you may be disappointed:
the actual core frequency of this processor is only 1.6GHz

The actual working frequency of this processor is 1.6GHz. When AMD faced some problems with increasing the ClawHammer core frequencies, they had to make the L2 cache bigger, to ensure adequate performance of the new CPUs. That is why our Athlon 64 2800+, working at pretty low actual core clock, features a 1MB L2 cache. The first mass Athlon 64 processors will have exactly the same L2 cache configuration. A bit later AMD will also launch a less expensive version with 256KB L2 cache.

By the way, you shouldn’t forget that Athlon 64, just like Athlon XP, features an exclusive L2 cache. In other words, taking into account the 128KB L1 cache (64KB for instructions and 64KB for data), inherited from Athlon XP, the overall cache memory of the new Athlon 64 makes 1152KB. The 0.13micron SOI technology used for Athlon 64 production allows placing so much cache memory on the same die with the actual CPU. As you may know, Intel will implement 1MB L2 cache only in Prescott processors, which will be manufactured with 0.09micron technology.