Intel has just come out with another version of Pentium III, code named Tualatin, which has a 512 KB L2 cache operating at the same clock frequency as the processor, thereby double the amount of cache memory offered by previous versions of Pentium III and, according, this processor is much faster than the traditional Pentium IIIs.

This reminds us that there are various different models of Pentium II on the market, and this ends up confusing users. It would be much simpler if the all these models merely differed in their clock frequency. However, several details result in the various completely different Pentium IIIs: type of connection, amount of L2 cache, external clock, etc.

As regards their mechanical design, there are two models of Pentium III, that is, this processor can be found with two different types of connector, and the motherboard has to match the type of connection used by the processor. The first models of Pentium III to come onto the market were cartridge-mounted, resembling the design used for the Pentium II, known as SECC-2. These models are plugged into the motherboard via a connector called Slot 1 or SC-242. Some time after, Intel marketed FC-PGA Pentium IIIs, in which the plug-in system is a socket known as socket 370. Note that the cartridge assembly models continued to be manufactured even after the socket model came onto the market.

Models of Pentium III up to 600 MHz utilize a 512 KB cache memory circuit operating at half the processor's clock frequency - for instance, in a Pentium III-600, the L2 cache is accessed at 300 MHz. After the 650 MHz model, Intel then came out with a Pentium III with a cache clocked at the same frequency as the processor, albeit lowered to 256 KB. And now, as we said, the new models (from 1.13 GHZ) utilize a 512 KB cache running at the same frequency as the processor's internal clock. Note that there is more than a single model of Pentium III for the various clocks. For instance, the 600 MHZ model is available either with 512 KB of L2 cache at half frequency or 256 L2 cache at the same frequency. In such cases, a letter E is added to the processor's name to indicate the 256 KB cache.

Pentium III's external clock can be either 100 MHz or 133 MHz. Models with clocks that are factors of 50 (500, 550, 600, 650, etc) utilize a 100 MHz external clock. On the other hand, models with clock factors of 33 (733, 866, 933, etc) utilize a 133 MHz external clock. Some clocks are factors both of 50 and 33 and according models both with 100 MHz clocks and 133 MHz clocks have come out, those running at 133 MHz providing the best performance. In this case, a letter B has been added to the designation of 133 MHz models to distinguish them from 100 MHz models.

The following table sums up all these characteristics. The quickest way to find out the internal characteristics of your Pentium III is running an ID program, such as Wcpuid (available at http://www.hardwaresecrets.com/page/download). This kind of program runs a processor identifying instruction called CPUID, which for all Pentium III models returns the following values: string = "GenuineIntel";type = "0"; family= "6". However, field Model of this instruction will depend on the kind of Pentium III, according to the table.

Models	External Clock	Mechanical Design	L2 Cache	CPUID
1.13, 1.26 and 1.40 GHz	133 MHz	FC-PGA2	512 KB, same frequency	Model 11
1.13 GHz, 1B GHz, 933, 866,800EB, 733, 667, 600EB and 533EB MHz	133 MHz	FC-PGA or SECC	256 KB, same frequency (models above 650 MHz or E models) or 512 KB, half frequency (models up to  600 MHz)	Model 7 (512 KB) or model 8 (256 KB)
1.10 GHz, 1 GHz, 900, 850,800, 750, 700, 650, 600E, 550E and 500E MHz	100 MHz	FC-PGA or SECC	256 KB, same frequency (models above 650 MHz or E models ) or 512 KB, half frequency (models up to 600 MHz)	Model 7 (512 KB) or model 8 (256 KB)
550, 500 and 450 MHz	100 MHz	SECC	512 KB, half frequency	Model 7