The AMD Athlon XP 2600+
The Thoroughbred Core Gets a Shot in the Arm...

By, Marco Chiappetta
August 21, 2002

It's hard to believe that it has been three years since the introduction of the first AMD Athlons.  To celebrate the occasion, AMD has unveiled two new processors in their Athlon XP lineup, the 2600+ and the 2400+.  The Athlon XP 2600+ is clocked at 2133MHz, and the 2400+ is clocked at an even 2GHz, making these two new processors the first AMD CPUs to officially break the 2GHz barrier.  The road to 2GHz was a rough one for AMD though.  They may have beaten Intel to the 1GHz mark in the Pentium III days, but with the release of the Pentium 4 Intel has been able to increase clock speeds almost at will.  This put AMD in a tough spot, forcing them to find ways to squeeze more performance out of the venerable Athlon.  The "Thunderbirds" and "Palominos" came and went, then last June the "Thoroughbreds" arrived on the scene.  With these latest CPUs, AMD has enhanced the "Thoroughbred" core, giving them the ability to hit much higher clock speeds than the original stepping.  We were lucky enough to get our hands on one of AMD's latest flagship processor, the Athlon XP 2600+, and have put it through its paces for you today...

Specifications of the AMD Athlon XP 2600+ Processor
A Metal Layer Here...Some Decoupling Caps There...

The Athlon XP 2600+ we received for testing was packaged in brown organic material (high-resolution scans below). AMD will eventually produce all of their CPUs using green packaging. The coloring has absolutely no effect on performance though, so don't fret if you order one and it isn't green!

     
CLICK ANY IMAGE FOR ENLARGED VIEW

Key Architectural Features of the AMD Athlon XP Processor:

  • QuantiSpeed Architecture for enhanced performance

  • Nine-issue superpipelined, superscalar x86 processor microarchitecture designed for high performance

  • Multiple parallel x86 instruction decoders

  • Three out-of-order, superscalar, fully pipelined floating point execution units, which execute x87 (floating point), MMX and 3DNow! instructions

  • Three out-of-order, superscalar, pipelined integer units

  • Three out-of-order, superscalar, pipelined address calculation units

  • 72-entry instruction control unit

  • Advanced hardware data prefetch

  • Exclusive and speculative Translation Look-aside Buffers

  • Advanced dynamic branch prediction

3DNow! Professional technology for leading-edge 3D operation:

  • 21 original 3DNow! instructionsthe first technology enabling superscalar SIMD

  • 19 additional instructions to enable improved integer math calculations for speech or video encoding and improved data movement for Internet plug-ins and other streaming applications

  • 5 DSP instructions to improve soft modem, soft ADSL, Dolby Digital surround sound, and MP3 applications

  • 52 SSE instructions with SIMD integer and floating point additions offer excellent compatibility with Intel's SSE technology

  • Compatible with Windows XP, Windows 98, Windows 95, and Windows NT 4.x operating systems

266MHz AMD Athlon XP processor system bus enables excellent system bandwidth for data movement-intensive applications:

  • Source synchronous clocking (clock forwarding) technology

  • Support for 8-bit ECC for data bus integrity

  • Peak data rate of 2.1GB/s

  • Multiprocessing support: point-to-point topology, with number of processors in SMP systems determined by chipset implementation
    Support for 24 outstanding transactions per processor

Other Architectural Elements:

  • The AMD Athlon XP processor with performance-enhancing cache memory features 64K instruction and 64K data cache for a total of 128K L1 cache.  256K of integrated, on-chip L2 cache for a total of 384K full-speed, on-chip cache.

  • Socket A infrastructure designs are based on high-performance platforms and are supported by a full line of optimized infrastructure solutions (chipsets, motherboards, BIOS). Available in Pin Grid Array (PGA) for mounting in a socketed infrastructure Electrical interface compatible with 266MHz AMD Athlon XP system buses, based on Alpha EV6 bus protocol

  • Die size: approximately 37.6 million transistors on 84mm2. Manufactured using AMD's state-of-the-art 0.13-micron copper process technology.


    

If you read any of the AMD Athlon XP 2200+ reviews posted when that processor launched, you were probably a bit disappointed in the overclocking results reported by most of the on-line publications, including ours. After those reviews went live, we began to wonder if the new "Thoroughbred" core would be able scale to clock speeds approaching 2GHz. Well, the resounding answer is YES! But how did AMD do it when the 2200+ was barely hitting 1900MHz? Well, we'll let them tell you. Here's a quote taken directly from AMD...

"AMD continually strives to deliver the performance customers want. AMD has successfully implemented a process change for the "Thoroughbred" processor core that involved adding an additional layer of metal to reduce resistance and capacitance. AMD has also engineered additional decoupling capacitors to reduce electro magnetic interference. Finally, AMD always takes an active approach to rebalance and improve speed paths throughout the processor core design."

AMD has implemented a mask set change that allowed them to improve signaling into the processor. If you look at the chart and illustrations above, you'll notice that the changes were fairly significant. The new AIUAB stepping of the "Thoroughbred" core actually incorporates about 100K more on-die transistors, roughly the amount of transistors that made up a complete 80286 CPU! The additional transistors slightly increased the die size to 84 square millimeters, up from 80 in the original "Thoroughbreds". These changes probably cost AMD a pretty penny though, a .13 micron mask set could cost as much as $1 million US is some circumstances. It was money well spent in our opinion though. As you'll see later on, this CPU turned out to be a real screamer...

 

Processor ID and Overclocking