Athlon 64 X2: AMD's Dual-Core
In 2005, AMD changed its architecture to offer a dual-core version of the K8, and the Athlon 64 X2 was born. Though made up of two K8 cores, the architecture—using a HyperTransport interface—enabled good performance, unlike the solution used by Intel, with the FSB handling communication between the CPUs in its first dual-core processors. The Athlon 64 X2 exists in different sockets and is still on the market (as of August 2008) as an entry-level solution.
| Code name | Toledo | Brisbane |
| Date released | 2005 | 2006 |
| Architecture | 64-bits | 64-bits |
| Data bus | 64-bits | 64-bits |
| Address bus | 64-bits | 64-bits |
| Maximum memory | 1 TB | 1 TB |
| L1 cache | 64 KB + 64 KB x 2 | 64 KB + 64 KB x 2 |
| L2 cache | 1,024 KB x 2 (CPU frequency) | 512 KB x 2 (CPU frequency) |
| Clock frequency | 2,200-2,400 MHz | 1,900-3,100 MHz |
| Memory controller | DDR-400, 2 channels | DDR2-800, 2 channels |
| FSB | 1,000 MHz (HTT) | 1,000 MHz (HTT) |
| FPU | built-in | built-in |
| SIMD | MMX, Enhanced 3DNow!, SSE, SSE2, SSE3 | MMX, Enhanced 3DNow!, SSE, SSE2, SSE3 |
| Fabrication process | 90 nm | 65 nm |
| Number of transistors | 233.2 million | 153 million |
| Power consumption | 89/110 W (TDP) | 65/89 W (TDP) |
| Voltage | 1.35–1.4 V | 1.25–1.35 V |
| Die surface area | 199 mm² | 126 mm² |
| Connector | Socket 939 | Socket AM2 |
As for the Athlon 64, we’re only showing two versions of the K8, though other versions exist. Obviously there are server versions (Opteron), high-end versions (Athlon 64 FX) and mobile versions (Turion 64 X2), and also entry-level versions in the form of the Sempron X2. One final anecdote: AMD got away with using the same code name for a processor as Intel had used: the Santa Rosa (a dual-core Opteron manufactured on a 90 nm process).