Monday, December 11, 2000		On Hardware

Duron — the cheaper alternative

WITH personal computers becoming common place in every home, the topic of computer components that was hitherto limited to the computer savvy, is now commonly discussed by most computer literate people. All processor manufacturers are trying to aggressively push their products, leaving the user confused over the technical jargon and claims of superiority by chip manufacturers like AMD and Cyrix. There is no doubt that the consumer is the king and has a wide choice from among the processors available in the market, but how does he choose?

Currently Intel is marketing four types of processors namely Pentium IV, Pentium III and Celeron. Having discussed the Intel processors earlier, lets look at AMD in this issue. AMD has two processors in the market viz. AMD Athlon and Duron. AMD has also come out with a high-end version of Athlon nicknamed "Thunderbird". The Athlon is a high performance and high-end processor, which is priced higher and in the range of Pentium III processors. Duron is AMD’s answer to Intel’s popular budget range processor Celeron. Duron is, without doubt, a powerful CPU in a low-end price range. Cyrix has been deliberately left out, as it does not directly compete in the budget range that is limited to Intel Celeron and Duron.

Duron processors outclass competition on following counts.

High-Speed System Bus: The AMD Duron processor features a 200MHz front side system bus, which offers far more bus bandwidth compared to Intel’s Celeron processor. This bus speed is even higher than the highest available Front Side Bus (FSB) of 133 MHz in Pentium III processors. A higher FSB directly co-relates into faster computing and is felt in applications like large data processing, MP3 encoders, video encoders, soft DVD players, and basic video-editing packages.

Improved Cache Architecture: Another distinguishing feature of AMD processors is better Cache architecture and more on-chip cache i.e. 192 K as compared to 128 KB on Intel’s Celeron processors. The cache architecture is such that it has 128 KB L1 full speed cache and an exclusive 64 KB L2 full speed cache. Moreover, it also has 2-Way Set Associative 64-Bit Wide Bus. Both, Pentium-III while Celeron has conventional inclusive L2 cache, which means that all of the data stored in their L1 cache (32KB) is duplicated in their L2 cache (256KB in case of Pentium III or 128KB in case of Celeron). So, while the Pentium III has 256KB of L2 cache, 32KB of that is actually duplicated from what is in the L1 cache. The same goes for Celeron which features 128KB of L2 cache, 32KB of which is a duplicate of everything stored in its L1 cache. However, it is not the case in Duron as it has Exclusive L2 cache, thus it does not duplicate L1data in the L2 cache area.

Moreover, the L2 cache only contains the copy-back cache blocks that are to be written back to the memory sub system (basically everything that doesn’t fit in L1 and would normally go to the system memory if there was no L2 cache).

Here it is very important to understand that though Duron only has a 64KB L2 cache, it does not contain a copy of the L1 cache as it is the case in Celeron and Pentium-III and thus works along side it to store a total of 192KB of frequently used data (128KB L1 + 64KB L2). Now if on these lines we compare the cache of Celeron, then its inclusive L2 cache duplicates everything stored in L1, meaning that the 128KB L2 is reduced to a usable 96KB L2 only. Because of this, Celeron actually only has 128KB of cache in which it can store frequently used data, same as in case of Pentium III.

However, all is not well with Duron, it has its weak points too. It lags behind Celeron on its 64 bit data path to L2 cache, which is significantly lower in comparison to the 256 bit data path of Pentium – III and Celeron 533A, 566 and above. The lower bandwidth of data path to L2 cache being one of its drawbacks, but it is adequately compensated by other superior features of the processor.

The reason why Celeron under performs in comparison to Duron, despite a higher clock speed of 700 MHz, is because Celeron’s L2 cache features a 4-way set associative mapping algorithm, whereas Pentium-III features 8-way set associative L2 cache. However, the Duron processors can retain 16-way set associative L2 cache, because it’s core is physically small, which clearly makes it a winner over a Celeron processor. The sophisticated cache architecture, delivers superior performance in comparison to Intel’s Celeron processor on memory-intensive applications like business and personal productivity suites, as well as basic 3D content creation and photo-editing packages.

Superscalar Floating Point Unit with Enhanced 3DNow! ™ Technology: The 3D Now! ™ Technology of AMD is yet another scoring points of this processor. This technology with three floating point pipelines give a better performance in comparison to other processors in its range. This also compares well with the Intel’s Celeron processor, which features only one floating-point pipeline. So, the difference in performance could be well reflected in case of multimedia and specially the graphics based applications as AMD’s patented 3D now technology added more spices to the Duron experience. Thus AMD Duron processors can offer better performance in applications like Web designing; animation and graphic rich educational and entertainment-based applications.

There are several other features that make AMD’s Duron stand apart. On testing parameters, it compares very well with Pentium-III, even though the Pentium-III is a class higher. This processor can be a good alternate for the home computers and also for small offices, where Intel Celeron finds good applications.

Currently in the Indian market, the Duron processor is available with clock speeds between 600 MHz to 750 MHz, though a 800 MHz Duron has also been launched in international markets. The maximum speed projected for these processors as of now is 1 GHz, which is likely to be launched in the first quarter of the next year.

— V.V