At last! After being pushed back several times, the AMD Bulldozer architecture has arrived on the market. Its roll-out on AM3+, codename Zambezi, is under the AMD FX brand, a name which recalls the glorious period of the K8 during which AMD did some serious damage to Intel and its Pentium 4s. Will the AMD FX live up to its name?
A high frequency CMT architectureWe did devote an article to Bulldozer last spring but it may be of some use to run back over the main points.
An 8-core processor is in fact made up of 4 modules. Within a module, the two cores share a certain number of components:
- the front-end which groups the fetch unit and instruction decoding as well as the L1 instruction cache which is supplied by these units;
- the floating point unit;
- the L2 cache.
AMD is claiming 80% of the performance of two full cores for major efficiency improvements in terms of silicon area and energy consumption. Many other changes have also been made, both to the processing units themselves and the memory sub-system, in particular so the architecture can clock higher.
Bulldozer also supports 100% of current x86 instruction sets and is compatible with the latest versions of SSE4 (4.1 and 4.2) and AES-NI instructions which enable encryption acceleration. AVX, introduced by Intel with Sandy Bridge, and its 256-bit operands are included.
Note also some instructions specific to Bulldozer have been introduced, grouped under the following: XOP, FMA4 and CVT16. These instruction sets actually correspond to SSE5 (announced by AMD in 2007 but never implemented) adapted to the AVX format. XOP operates mainly on integer operands, FMA4 on 128-bit floating point numbers and CVT16 groups high precision floating point conversion instructions to medium and low precision floating points. FMA4, which allows the processing of a multiplication and addition in a single cycle, should, among other things, enable gains when used by applications, however a different version, FMA3, will be used by Intel. AMD will follow suit here, with Piledriver, the development of Bulldozer, adopting FMA3 and calling the durability of FMA4 into doubt.