Monday, November 13, 2000		On Hardware

Celeron vs Pentium III

THE most confusing word in computer terminology is speed. A buyer often goes in for the fastest processor while purchasing a computer. Speed is, however, subjective. A Hindi idiom says "Jahan kaam aaye sui, kya kare Talwaar (No matter how mighty a sword is, it cannot be a replacement for a needle). Going by this concept, the choice of a processor should largely depend on the requirement of work that is to be done on it and not on speed.

Normally, while planning to buy a computer prospective buyers think in terms of Pentium III and often ignore Celeron processors. Celeron processors did not get good reviews when they were launched in 1998. Despite the fact that Intel fixed the problems in Celeron processors long ago, the initial negative impression has not changed. However, ignorance comes with a price that a person pays when he opts for Pentium III, even though Celeron processor-based computer could manage his work. This does not mean that Pentium II or Pentium III processors are not good.

Take a close look at Celeron 600 MHz processor. You will find that the clock speed of the Celeron processor is same as the clock speed of Pentium III 600 MHz processor. The difference is that Celeron chip is based on Pentium II core while Pentium III chips are based on a Pentium III core.

The Pentium III core contains an enhanced instruction set in comparison to the Celeron chip and it also has some pipelining improvements that give a slightly better performance on normal instructions. The questions are: "How many sets of instructions are required for the kind of work and what are the sets of instructions available in the Celeron processor." It’s really not possible to quantify the sets of instructions for any application. But as per the general norms, the number of instruction available in a Celeron chip are sufficient enough to perform efficient applications like word processing and other normal computer usage.

Moreover the enhanced instruction set is only useful to programs specially coded to take advantage of it, and it is worth mentioning here that there are not that many applications to take advantage to higher set of instructions.

For normal computer usage like word processing, Internet browsing and other applications including the games, the Celeron chip-based computers are sufficient enough.

One more significant difference between a Pentium-III based computer and a Celeron processor-based computer is of cache memory. Normally, Pentium III uses a separate chip for its processor cache while the Celeron has on-chip cache. This means that Celeron has one half or one quarter the amount of cache of most Pentium IIIs, but Celeron’s cache runs twice as fast in comparison to the Pentium III processor. Celeron processors incorporate separate 16 KB level-one caches (32 KB total), a 16 KB cache for instructions and 16 KB for data. But it also has a 128 KB unified, non-blocking, Level-2 full speed cache, which improves performance by reducing the average memory access time and providing fast access to recently used instructions and data. Integrated 128 KB L2 cache is available in versions that are built both on Intel’s 0.25 micron CMOS process technology as well as Intel’s advanced 0.18 micron CMOS process technology.

Thus, the concept that Celeron processors have no cache or the Celeron chip does not have L2 cache is absolutely wrong and baseless. Celeron also has a pipelined Floating-Point Unit (FPU) for supporting the 32-bit and 64-bit formats specified in IEEE Standard 754, as well as an 80-bit format.

Another difference between Celeron and Pentium-III processors is of bus speed. Most of the Celeron-based processors have 66 MHz Intel P6 micro-architecture’s multi-transaction system bus whereas Pentium-III processors normally have a system bus of 100 MHz. There are some Pentium-III processors like 667E MHz and 733 MHz that uses 133 MHz FSB bus, which are supposed to be much faster than the 100 MHz bus speed processor.

The clock speed of the latest Pentium –III processors is much higher than the latest Celeron processor. This also has a psychological impact on the user about the choice of the processor as the speed factor plays a vital role in choosing the processor for the computer. On analysis, it turns out that a Celeron and a Pentium III chip, running at the same speed are identical in performance as far as the home use of a computer is concerned. A 500 MHz Pentium III or a 500 MHz Celeron processor give an identical level of performance for a home-based PC or a PC that is intended to be used for purposes, that are not very technical and do not involve excessive data processing. On major counts like cache, Celeron’s smaller cache size is mitigated by the speed of the cache, and the extra instructions in the Pentium III go unused. Thus, for a common man, a very high end processor does not necessarily mean high value for money. Celeron processors are much cheaper in comparison to the Pentium III based computers. Looking at the price-to-performance ratio of both processors for a home-based PC or for a PC that is to be used for running normal applications, the Celeron processors can be a preferred.

— V.V.