One Product = Three Product Lines

Like the Pentium® II before it, three separate product lines were derived from the Pentium® III processor:

• The Pentium® III processor targeted the mid- to high-end desktop market and supported either one or two processors on the FSB.

• The Xeon processor (see “Pentium® III Xeon Features” on page 795 for more information on the Pentium® III-based Xeon). The Xeon targeted the workstation and server market and supported either two (a Xeon DP), or four (a Xeon MP) processors on the FSB. With the following exceptions, the Xeon was identical to the Pentium® III:

  - While various models of the Pentium® III had L2 Cache sizes of 128KB or 512KB, the Pentium® III Xeon was available with a 256KB, 512KB, 1MB, or 2MB L2 Cache.

  - While the Pentium® III's BSB operated at 50% of the processor's core speed, the Pentium® III Xeon's BSB operated at 100% of the core speed.

  - The Xeon implemented a Processor Information ROM, a scratch EEPROM and a thermal diode that could all be read from over the serial SMBus.

  - The Pentium® III implemented two pins (BR[1:0]#) for FSB arbitration, permitting two processors on the FSB. The Xeon MP implemented four pins (BR[3:0]#), permitting four processors on the FSB.

• The Celeron processor. The Pentium® III Celeron targeted the low-end desktop market and only supported one processor on the FSB. With the following exceptions, the Celeron was identical to the Pentium® III:

  - The Pentium® III implemented two pins (BR[1:0]#) for FSB arbitration, permitting two processors on the FSB. The Celeron implemented one pin (BR0#), permitting one processor on the FSB.

  - The FSB speed (i.e., the BCLK frequency) of the Celeron was slower than that of the Pentium® III.