athlon 64

Athlon

The Athlon 64 (codenamed "ClawHammer", "Newcastle", "Winchester", and "Venice") represents AMD's entry into the consumer 64-bit microprocessor market, released on September 23rd, 2003. This processor is based on the AMD64 architecture. It is AMD's first eighth generation processor core (K8) for desktop and mobile computers. There are two variants: Athlon 64 and Athlon 64 FX. The Athlon 64 FX is positioned as a hardware enthusiast product, always one speed step above the fastest Athlon 64. As an implementation of the AMD64 architecture, the Athlon 64 is able to run 32 bit x86, 16 bit, and AMD64 code.

Features

The Athlon 64 features an on-die memory controller, a feature not previously seen on x86 CPUs. Not only does this mean the controller runs at the same clock rate as the CPU itself, it also means the electric signals have a shorter physical distance to travel compared to the old "northbridge" interfaces. The result is a significant reduction in latency (response time), for access requests to main memory. Translation Look-Aside Buffers (TLBs) have also been enlarged, with reduced latencies and improved branch prediction, with four times the number of bimodal counters in the global history counter. This and other architectural enhancements, especially as regards SSE implementation, improve instruction per cycle (IPC) performance over the previous Athlon XP generation. To make this easier for consumers to understand, AMD has chosen to market the Athlon 64 using a PR rating system, where the numbers roughly map to Pentium 4 performance equivalents, rather than actual clock speed. Athlon 64 also features CPU speed throttling technology branded Cool 'n' Quiet. When the user is running undemanding applications and the load on the processor is light, the processor's clock speed and voltage are reduced. This in turn reduces its peak power consumption (max TDP set at 89 W by AMD) to as low as 32 W (stepping C0, clock speed reduced to 800 MHz) or 22W (stepping CG, clock speed reduced to 1 GHz). NX bit supported by Windows XP service pack 2 is also included, for improved protection from malicious buffer overflow security threats. Hardware set permission levels make it much more difficult for malicious code to take control of the system. It is intended to make 64-bit computing a more secure environment. The Athlon 64 CPUs have been produced with 130 nm and 90 nm SOI process technologies. Only a few of the latest chips (Athlon 64 3000+, 3200+ and 3500+ for the Socket 939) have been on 90 nm so far.

Sockets

754: The Athlon 64 value/budget line, 64-bit memory interface (Single-Channel)
939: Athlon 64 performance line and newer Athlon 64 FXs, 128-bit memory interface (Dual-Channel)
940: Opteron and old Athlon 64 FX, 128-bit memory interface - Requires registered DDR memory, but can use ECC

At the introduction of Athlon 64 in September 2003, only Socket 754 and Socket 940 were available. However, because scaling clock speed proved harder than anticipated, AMD decided improving the memory controller was the best available short term option. So as a stopgap measure, they brought out a non-multiprocessor version of the Opteron called the Athlon 64 FX, as an multiplier unlocked enthusiast part for Socket 940, comparable to Intel's Extreme Edition Pentium 4s. In June 2004, AMD released Socket 939 as the mainstream dual channel Athlon 64 memory interface, leaving Socket 940 solely for the server market (Opterons), and relegating Socket 754 as a value/budget line, for Semprons and slower versions of the Athlon 64. Eventually Socket 754 will permanently replace Socket A for Semprons. AMD also appears to be planning a new socket architecture to succeed Socket 939, codenamed M2. Socket M2 is expected to come out in the first half of 2006, and it will support DDR-2, security and virtualization features.

Future

AMD is due to release a new stepping (E0) in April 2005, which brings SSE3 instruction set support, updates to the memory controller, process technology upgrade from 130 nm to 90 nm in the 3800+ and 4000+ models and reduced power requirements thanks to a new type of strained silicon called dual stress liner strained silicon. These will potentially allow Athlon 64 to be clocked past 3.0 GHz, corresponding to a PR rating of 4500+ or higher. In mid-2005 AMD will release dual-core processors based on the K8 core, but the Athlon 64 product line will not have dual-core offerings. Instead, dual-core processors will be offered in the Athlon 64 FX and Opteron product lines. AMD demonstrated a four-way dual-core (8 cores in total) Opteron server on September 1st, 2004. The dual-core processors will start out at the 90 nm process technology. AMD claims the K8 core was designed for dual-core capabilities from day one.