KarbosGuide.com. Module 3e.08b

AMD K7 "The Great" Athlon.

The contents:

  • The Athlon Tbird
  • The Sledgehammer
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  • The Thunderbird Athlons

    The Athlon processor has a very large potential. Back in 1999 some analytics believed that Athlon will be the most important and dominant processor in 2001. And they were almost right. All major vendors - except Dell - are using Athlons in high-end PCs.

    The Athlon has an enormous bandwidth that obviously not will be needed in the immediate future.

    The point is that the architecture is looking ahead. There is lots of room for technological advances in the coming years, such as significantly faster RAM, hard disk etc.

    At the same time AMD signals that this is the future server architecture, since especially larger network servers will have a need for the large bandwidth.

    The Thunderbird core

    AMD has a new fabrication unit (fab 30) in Dresden, Germany. From this the new "Thunderbird" core was shipping June 2000.

    The first Thunderbirds:

  • 750 MHz to 1 GHz versions using 0.18 micron copper technology.
  • 256 KB L2 cache integrated.
  • New 462 pin socket A.
  • Both copper and aluminium chips available.

    The Thunderbird is a very powerful chip with its 37 million transistors. It competes directly with the Pentium III "Cumine".

    The "old" Athlon design using a Slot A-based cartridge suffered from poor L2 cache performance. The 512 KB of L2 cache was placed outside the CPU. This gave a connection to the CPU working at only a half or a third of the processors clockspeed.

    Integrating the L2 cache with the processor, the 256 KB is accessed at full processor speed, as it should. On-die cache gives the best performance. The reduction in the L2 size from 512 to 256 KB is of less importance; the full clockspeed has an enormous effect.

    The Thunderbird chip performs just as good as or slightly better than Pentium III running at the same clock frequencies. With the new on-die L2 cache of 256 KB in combination with the original 128 KB L1 cache, AMD indeed has a very powerful product.

    Narrow L2 cache to CPU pipeline

    Still Pentium III Cumine has one advantage to the Thunderbird. When Intel decided to integrate the 256 KB of L2 cache with the processor, they gave it a 256 bit wide bus to work with.

    When the L2 resides outside the CPU you have to stick to a 64 bit bus between CPU and L2. This restriction comes from the number of CPU pins you want to allocate to the L2 connection.

    If the L2 cache is integrated with the CPU there is no need for this limitation. Intel wisely went from 64 to 256 bits width. This AMD has not done. For some reason, the Thunderbird core still only connect to the L2 cache on a 64 bit wide bus.

    Copper or alu?

    The new Thunderbirds are being produced two fabs:

  • At fab25 in Austin, Texas (0.18 micron aluminium)
  • At fab30 in Dresden, Germany (0.18 micron copper)

    AMD told that there should be no difference between the two chips.

    Copper is the most sophisticated material since it opens up for much higher clock frequencies than aluminium, due to the better electrical conduit. However, at sub-GigaHertz frequencies aluminium works fine, and there should be no difference between the chips coming from different fabs.

    Chip sets

    The original Athlon chip set AMD 750 works fine with the Thunderbird processor. However, AMD is soon introducing the 760 chipset for use with Thunderbird. It is expected to support DDR RAM.

    The popular VIA KX133 chip set had problems with Thunderbird. Therefore VIA produced the KT133 chipset specially designed for Thunderbirds and Durons. This chipset was at first introduced as "KZ133" which was a very unwise choice in naming. KZ was the Nazi-German abbreviation for concentration camp - the camps in which millions of Jews and other Europeans were murdered. VIA wisely renamed the chip set when the historical significance of the two letters KZ came to their minds.

    Another brand of Athlon is the "Spitfire" core, which was launched as "Duron" for cheaper PCs - Celeron-killer so to say. Please see module3e13 on this chip.


    The successor to Athlon is codenamed "Sledgehammer". It sounds interesting:

  • Multi-core technology with several complete microprocessors working parallel within the same CPU.
  • The IA32 set of instructions are beeing extended to include a 64 bit mode.
  • More powerfull FPU.

    The value of 64 bit instructions is disputeable. We already have 64 bit and even 128 bit instructions within SSE and 3DNow!. Here it means new 64 bit instructions, registers, busses and memory addresses. To benefit fully from this 64 bit power, all software have to be recompiled. But AMD claims that the processor will run all existing 32 bit software at full speed as well.

    From my humble viewpoint, "Sledgehammer" (what a name) sounds far more interesting than Intel's Itanium. Backward compatibility has always been extremely important.

    Lots of RAM

    One of the limitations of the 32 bit architecture is the amount of RAM. A 32 bit processor can "only" address 4 Gb of RAM. This is not enough for the biggest systems.

    With 64 bit addressing you can use 18 Exebytes of RAM. That's a lot.

    Sledgehammer will be introduced in 2002.

    Please also see the article on die sizes here.

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    Learn more

    Read about chip sets on the motherboard in module 2d

    Read more about RAM in module 2e

    Read module 5a about expansion cards, where we evaluate the I/O buses from the port side.

    Read module 5b about AGP and module 5c about Firewire.

    Read module 7a about monitors, and 7b on graphics card.

    Read module 7c about sound cards, and 7d on digital sound and music.

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