Hardware Reference
In-Depth Information
processors to integrate the memory controller, and also includes the first truly integrated dual-core
processors. Although early versions of the K8 family were plagued by frequent socket changes, recent
and current versions of the family offer an easy upgrade path to more advanced designs and DDR2
and DDR3 support.
AMD Athlon 64 and 64 FX
The AMD Athlon 64 and 64 FX, introduced in September 2003, are the first 64-bit processors for
desktop (and not server) computers. Originally code-named ClawHammer, the Athlon 64 and 64 FX
are the desktop element of AMD's 64-bit processor family, which also includes the Opteron (code-
named SledgeHammer) server processor. The first Athlon 64 and 64 FX (shown in
Figure 3.39
)
are
essentially Opteron chips designed for single-processor systems. In some cases, they have decreased
cache or memory bandwidth capabilities.
Figure 3.39. AMD Athlon 64 FX (Socket 939 version). Photo courtesy of AMD.
Besides support for 64-bit instructions, the biggest difference between the Athlon 64 and 64 FX and
most other processors is the fact that their memory controller is built in. The memory controller is
traditionally normally part of the motherboard chipset North Bridge or Memory Controller Hub
(MCH) chip, but the Athlon 64 and 64 FX incorporate the memory controller in the processor. This
means that the typical CPU bus architecture is different with these chips. In a conventional design, the
processor talks to the chipset North Bridge, which then talks to the memory and all other components
in the system. Because the Athlon 64 and 64 FX have integrated memory controllers, they talk to
memory directly, but they also talk to the North Bridge for other system communications. Separating
the memory traffic from the CPU bus allows for improved performance not only in memory transfers,
but also in CPU bus transfers. The main difference in the Athlon 64 and 64 FX is in the configurations
of cache sizes and memory bus widths.
Following are the major features of the Athlon 64 design:
• Speeds ranging from 1.0GHz to 3.0GHz.
• Between 68.5 million transistors (512KB L2 cache versions) and 129 million transistors (1MB
L2 cache versions).
• 12-stage pipeline.
• DDR memory controller with ECC support integrated into the processor (instead of the North
Bridge or MCP, as in other recent chipsets).
