Intel 440BX

The Intel 440BX, also known as the i440BX, is a chipset from Intel, supporting Pentium II, Pentium III, and Celeron processors. It was released on April 1998.

Features

Intel 82443 (440BX northbridge) on an Abit BF6

The i440BX chipset uses a slotket adapter, which allows plugging both Slot 1 and Socket 370 CPUs. It supports Pentium III CPUs (Tualatin core) in single and dual processor configurations, at speeds up to 1.4 GHz. It uses Intel 82443 chip as the northbridge and Intel 82371EB as the southbridge. The FSB runs at 100 MHz, which provides support for Intel P6-based processors. The chipset is equipped with Intel's second generation AGP 2x technology.

Tualatin processors can form the basis of an inexpensive upgrade since the Celeron version has a front side bus speed of 100 MHz which matches the 440BX's officially supported 100 MHz FSB speed. Indeed, the Tualatin-based Celeron is superior in every respect to the previous generations of Pentium III. However, it cannot be run in a SMP configuration.

History and rise to fame

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 aged 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 Bus 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. And years later the 130 nm Tualatin-based Pentium III, using an adapter, allowed 440BX-based systems a renewed lease on life.

Ironically, the 440BX offered better performance than several of its successors. The i810 and i820 chipsets were unable to best the 440BX at the 100 MHz FSB speed. The i820 was plagued with a requirement for high cost RDRAM to reach good performance, along with a string of reliability issues involving a SDRAM-to-RDRAM memory translator hub. And, unofficially, the 440BX could often be taken to 133 MHz FSB. Enthusiast motherboards, such as the Asus P3B-F and Abit BH6/BF6/BE6 series, were equipped with BIOS options to set the board to this unofficial speed. With a 133MHz FSB, the 440BX could even match the later i815 chipset, which was designed to accommodate the final Tualatin-core Pentium III. Unfortunately, running a 440BX above 100 MHz FSB resulted in the AGP video card being forced to run on an overclocked AGP bus, as the 440BX only had "2/3" and "1/1" bus dividers. Some video cards were tolerant of this, such as various early NVIDIA GeForce cards, but more than a few were quite unstable with a 35% AGP overclock.

Still, the later i815 was considered the best Pentium III chipset because it offered a better feature-set and very similar performance relative to the 440BX. Not only did the i815 support a proper "1/2" AGP divider for the 133 MHz FSB clock rate, AGP 4x, and Ultra DMA 100, but the later revisions also directly supported the Tualatin Pentium III.

The success of the 440BX chipset has caused various software emulation and virtualization packages to use it as part of their virtual system. VMware and Microsoft Virtual PC present the Intel 440BX chipset virtually to hosted virtual machines, due to its broad compatibility.

See also

• List of Intel chipsets

External links

• Celeron overclocking FAQ at Ars Technica, by Frank Monroe
• Asus P2B-D modification guide