Intel 440BX

The Intel 440BX (codenamed Seattle), is a chipset from Intel, supporting Pentium II, Pentium III, and Celeron processors. It is also known as the i440BX and was released in April 1998. The official part number is 82443BX.

The 440BX originally supported Slot 1 and later Socket 370 Intel P6-based processors in single and SMP configurations at speeds of up to 1 GHz (and potentially up to 1.4 GHz with certain unsupported modifications, up to 1.7 GHz can be achieved using Front Side Bus speeds higher than 133 MHz and appropriate cooling). Its southbridge counterpart is the PIIX4E.

The Intel 440BX is the third Pentium II chipset released by Intel, succeeding the 440FX and 440LX. With the new 100 MHz front side bus, Pentium II CPUs were able to scale better in performance by reducing the difference between processor clock and bus speed. The previous 66 MHz bus had become a serious bottleneck and dated back to the first Pentium "Classic" chipsets.

The 440BX had two closely related chipset peers; the 440ZX and 440MX. 440MX is a mobile chipset for laptops, although a number of notebooks did use 440BX. 440ZX is a cost-reduced version of 440BX. It has a lower maximum RAM limit resulting from having support for only 2 RAM banks. The 440ZX-66, designed for Intel Celeron processor, is limited to 66 MHz FSB speed.

The 440BX became one of Intel's most popular chipsets. Enthusiasts enjoyed its overclockability, with the chipset capable of running the front-side bus at speeds ranging from 66 MHz to well over 133 MHz, in stark contrast to the 440LX's struggle to top 75 MHz. A common overclock involved the pin-40 hack, or using an ABIT BH6 or Asus P2B, and setting the bus speed on a 66 MHz Covington or Mendocino-core Celeron to 100 MHz. The Mendocino-core Celeron 300A became a "sweet spot" for overclockers, with nearly 100% success rates at reaching 450 MHz on a 100 MHz FSB, allowing it to equate to a much more expensive Pentium II at 450 MHz. Other popular overclocks included the SL2W8-stepping Deschutes-core Pentium II that could often run to 450 MHz at 100 MHz FSB, and the SL35D Katmai-core Pentium III 450 MHz which could frequently manage 600 MHz on a 133 MHz FSB. The later Pentium III Coppermine-core processor was easily overclocked and performed well on 440BX motherboards. Finally, the unsupported Tualatin-core Pentium III could be used with an adapter and various modifications, with varying degrees of success.

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