There are many reasons the original Athlon performed so well.  First is because of it’s FPU  It had three, independent FPU units, that can do work at the same time.  As for the Pentium III CPU, if one of it’s pipelines got behind, all other pipelines wanting to to the same thing must stop and wait for it to get done.  This makes the Athlon truly a Seventh Generation Processor.  Another reason is because of it’s L2 cache.  On all of the older Slot A Athlons, the L2 cache toped out at 350Mhz.  When the core reached 750Mhz, AMD had to bring the L2 cache down to 40% of the processing core to fulfill the 350MHz maximum rating.  Then again at 900Mhz, they had to drop the L2 down to 33% of the core.  This made the 1GHz AMD Athlon Processor perform much worse than it’s Pentium III counterpart, once again putting Intel on top.  Later, AMD announced the second generation of it’s AMD Athlon Processor (mentioned below).  The “Thunderbird” as it was codenamed, moved the L2 cache on the core, providing a 100% Core/L2 ratio.  It also decreased the size by 50%, from 512KB, to 256KB.  AMD also changed Athlon’s cache from 2-way set associative to 16-way set associative, meaning the core should not need to access the slower system memory as often.

One notable feature of the Athlon is the new Slot interface. While Intel could play games by patenting Slot 1, AMD decided to call the bet by developing a Slot of their own – Slot A. Slot A looks just like Slot 1, although they are not electrically compatible. But, the closeness of the two interfaces allowed motherboard manufacturers to more easily manufacturer mainboard PCBs that could be interchangeable. They would not have to re-design an entire board to accommodate either Intel or AMD – they could do both without too much hassle. Another move by Intel which was called by AMD was the name “Athlon”. Reminicent of Intel’s breakage of the x86 naming platform with the Pentium release, AMD wanted to set the Athlon apart from previous processors with a new name. Hence, AMD abandoned the Kx naming structure and called its K7 “Athlon”.

Also notable with the release of Athlon was the entirely new system bus. AMD licensed the Alpha EV6 technology from Digital Equipment Corporation. This bus operated at 200MHz, faster than anything Intel was using. The bus had a bandwidth capability of 1.6 GB/s.

Here are the technical specs of the original Athlon as put forth by AMD:

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  Super-pipelined, nine-issue superscalar micro-architecture optimized for high clock frequency

  
  
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  Industry first, fully pipelined, superscalar floating point unit for x86 platforms

  
  
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  128KB of on-chip level-one (L1) cache

  
  
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  Programmable, high-performance backside L2 cache interface which can feature 512KB to 8MB of onboard running from 50% – 33% of core speed (Slot A)

  
  
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  Advanced, exclusive 256KB – 2MB ondie L2 cache running at 100% of core speed.

  
  
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  Enhanced 3DNow! technology

  
  
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  Alpha “Slot/Socket A” Interface using ALPHA Frontside Bus Protocol

Athlon has gone through revisions and improvements and is still being used and marketed. In June of 2000, AMD released the Athlon Thunderbird. This chip came with an improved 0.18 micron design, on-die full speed L2 cache (new for Athlon), DDR RAM support, etc. It is a real workhorse of a chip and has a reputation for being able to be pushed well beyond the speed rating as assigned by AMD. Overclocker’s paradise. Thunderbird was also released in Socket A (or Socket 462) format, so AMD was now returning to its socketed roots just as Intel had already done by this time.

In May 2001, AMD released Athlon “Palomino”, also dubbed the Athlon 4. While the Athlon had now been out for about 2 years, it was now being beaten by Intel’s Pentium IV. The direct competition of the Pentium III was on its way to the museum already, and Athlon needed a boost to keep up with the new contender. The answer was the new Palomino core. The original intention of Palomino was to expand off of the Thunderbird chip, by reducing heat and power consumption. Due to delays, it was delayed and it ended up being beneficial. The chip was released first in notebook computers. AMD-based notebooks, until this time, were still using K6-2′s and K6-3′s and thus AMD’s reputation for performance in the mobile market was lacking. So, Athlon 4 brought AMD to the line again in the mobile market. Athlon 4 was later released to the desktop market, workstations, and multiprocessor servers (with its true dual processor support). Palomino made use of a data pre-fetch cache predictor and a translation look-aside buffer. It also made full use of Intel’s SSE instruction set. The chip made use of AMD’s PowerNow! technology, which had actually been around since the K6-2 and 3 days. It allows the chip to change its voltage requirements and clock speed depending on the usage requirement of the time. This was excellent for making the chip appropriate for power-sensitive apps such as mobile systems.

When AMD released the Palomino to the desktop market in October of 2001, they renamed the chip to Athlon XP, and also took on a slightly different naming jargon. Due to the way Palomino executes instructions, the chip can actually perform more work per clock cycle than the competition, namely Pentium IV. Therefore, the chips actually operate at a slower clock speed than AMD makes apparent in the model numbers. They chose to name the Athlon XP versions based on the speed rating of the processor as determined by AMD and their own benchmarking. So, for example, the Athlon XP 1600+ performs at 1.4 GHz, but the average computer user will think 1.6 GHz, which is what AMD wants. But, this is not to say that AMD is tricking anybody. In fact, these chips to perform like the Thunderbird at the rated speed, and perform quite well when stacked against the Pentium IV. In fact, the Athlon XP 1800+ can out-perform the Pentium IV at 2 GHz. Besides the naming, the XP was basically the same as the mobile Palomino released a few months earlier. It did boast a new packaging style that would help AMD’s release of 0.13 micron design chips later on. It also operated on the 133MHz front-side bus (266MHz when DDR taken into account). AMD continued to use the Palomino core until the release of the Athlon XP 2100+, which was the last Palomino.

In June of 2002, AMD announced the 0.13 micron Thoroughbred-based 2200+ processor. The move was more of a financial one, since there are no real performance gains between Palomino and Thoroughbred. Nonetheless, the smaller more means AMD can product more of them per silicon wafer, and that just makes sense. AMD is really taunting everyone with news of the coming ClawHammer core, which will be AMD’s next big move. But, with that chip still in the development and testing phase at this point, ClawHammer is not yet ready. Until it is, AMD will keep us mildly entertained with Thoroughbred and keep Intel sweating.