first Pentium 4

The sockets

The first Pentium 4s came with a 423 pin design. These CPUs could only use RDRAM, which only requires few pins interface.

Later came a 478 pin design with support for SDRAM.

The chipsets

The chip set i850 ("Tehama") is using a dual RDRAM bus. This is also heating up the MCH (north bridge) chip, so additional cooling is required.

The Intel i845 chipset was introduced August 2001. It gives an interface to standard 133 MHz SDRAM. This chipset is found in many cheap Pentium 4 computers.

Support for 266 MHz DDR RAM is found in the VIA P4X266 and P4X266A chipsets to be used with Pentium 4 (against Intels will; they don't like VIA at all).

SIS 645 is a chipset for Pentium 4 with support for both 266 and 333 MHz DDR RAM.

The i845D chipset

December 2001 Intel suddenly introduced a new flavour of the 845 chipset. It is designed to use with DDR-RAM!

There was no press releases about this product. Searching Intel's web for info on this chipset gave no result (December 27th 2001):