Pentium 4 Northwood Overclocking Guide - Page 3

Back when the Pentium 4 was first released, there was really only one motherboard platform/chipset/memory format in use. The first chipset was the Intel 850 chipset, and the only compatible memory was RAMBUS RDRAM. Oh how the times have changed since then, and now there is a virtual cornucopia of DDR platform options available. Here is yet another chart that lists the most popular Pentium 4 chipset options, and outlines the main specifications for each:

Those looking to go the Intel route have the i845, i845E and i845G models , but if you want to stray from Intel chipsets, SIS has the 645 and 645DX chipsets and VIA offers up the P4X266A/E variants and their new P4X333. Of course for fans of RDRAM, you can still use motherboards utilizing the i850 or i850E chipsets. All of the newer chipsets featuring support for the 133/533MHz FSB and DDR333 are impressive, but there are a few issues present with some.

VIA Technologies produces Pentium 4 chipsets, but Intel has stated that the company does not have an official license to make and sell Pentium 4 chipsets. Whatever the courts end up deciding, this translates into a lukewarm reception for the P4X266 and P4X333 chipsets and there are very few prominent motherboard manufacturers even using VIA Pentium 4 chipsets. Intel has also created something of a conundrum in choosing a prime overclocking platform. Their i845 is a solid chipset, but it does not have support for the 133/533 MHz FSB. The i845E would be the natural choice, but this does not feature support for DDR333. The i845G has both required features, but buyers will need to pay a bit more for the integrated graphics core, as well as dealing with less-than robust i845G motherboard designs.

Not having official support for the 133/533 MHz FSB can cause problems with overclocking above the default 100 MHz FSB (standard) of the Pentium 4-1.6A, 1.8A and 2.0A processors. Chipsets such as the i845 and SiS 645 may not have the proper AGP/PCI dividers in place at higher-than 100 MHz FSB speeds, and can cause erratic performance or system instabilities.

For example, the PCI bus is specified to run at 33 MHz, therefore at 100 MHz, with a 1/3 divider, the PCI bus will run within specification. Raising the FSB to 110 or so, will also raise the PCI bus, but would unlikely cause any damage, because 110 divided by 3 would still be fairly close to the standard 33 MHz PCI speed. But using the same motherboard and setting the FSB to 133 MHz or beyond could cause some major problems with PCI devices or hard drives because with only a 1/3 divider, the PCI bus would be running at 44 MHz. Newer chipsets such as the SiS 645DX or i845E/G do away with these concerns by providing higher AGP and PCI dividers for use at the 133 MHz FSB. We should also note at this time that many i845D based motherboards (regardless of FSB speeds) lock their AGP and PCI frequencies at 66 and 33 MHz respectively, so there isn't a great danger to your peripherals when overclocking with many high-end i845 DDR motherboards.

Considering performance, stability, and availability factors, along with full support for the 133/533 MHz FSB and DDR333, the natural recommendation is a motherboard based on the SIS 645DX chipset. This is for new system purchases or upgrades, and we also realize there are also a huge number of i845 motherboard owners who may want to upgrade to some Northwood overclocking goodness. For this reason, we are including both sides of the coin, and offer i845D and SiS 645DX overclocking options and benchmarks a bit later in this guide.