The i850 was the first chipset released to support the Pentium 4 processor. Code named "Tehama", and based off the i840 workstation chipset for the Pentium III, it was launched with the Pentium 4 in November 2000. The only substantive differences between the i840 and i850 are processor bus support and lack of SMP support on the i850. Both chipsets feature a dual-channel RDRAM controller for huge piles of memory bandwidth, ATA-100, AGP 4X, and USB 1.1. It was the first chipset to require an ATX 2.03 power supply with ATX12V and auxiliary power connectors, necessitating power supply upgrades from most everyone.
The i850 was the only Pentium 4 chipset available for the first six months of the Pentium 4's availability. Coupled with the high relative price of RDRAM and the dual-channel memory controller's requirement for paired RIMMs, this caused significant problems for the adoption of the Pentium 4. In fact, for a relatively long time, all retail Pentium 4 processors came bundled with 128 MB of RDRAM in two 64 MB RIMMs. By the time the i845-D DDR SDRAM chipset came out, the price of RDRAM was not greatly larger than that of DDR, although this was due almost as much to rising DDR prices as it was to falling RDRAM prices.
The i850 was a very fast chipset on release, and it remained the fastest Pentium 4 chipset for over a year, until DDR333 chipsets from VIA and SiS as well as Intel's own i850E and i845E were released. The dual-channel RDRAM controller provided enough memory bandwidth to saturate the 100 MHz quad-pumped FSB of the Pentium 4. The primary disadvantage to the i850 chipset throughout this time was cost; mainboards based on the 850 were significantly more expensive than those based on other chipsets. The i850 was finally retired in May 2002, replaced by the i850E with support for the 133 MHz quad-pumped processor bus.
This writeup is copyright 2002 D.G. Roberge and is released under the Creative Commons Attribution-NoDerivs-NonCommercial licence. Details can be found at http://creativecommons.org/licenses/by-nd-nc/2.0/ .