Chipsets for the Pentium 4
The 850 is Intelís high end solution for the Pentium 4, mainboards based on
the 850 chipset cost more and use the more expensive RDRAM memory.† The 850
uses a dual-Rambus channel memory architecture; this requires that you install
the RIMM modules in pairs of two. The dual Rambus channel helps the latency
issues to be lessened and at the same time doubles the bandwidth of the memory.†
The 850 offers the standard features that Intel's ICH2 hub has to offer, this
includes ATA/100 support, an additional USB hub resulting in a total of four
USB ports, the implantation of the AC97 audio and 10/100Mpbs LAN. The North Bridge features support for the Pentium 4
processor running at 400MHz Quad Pumped Bus, support for 2GB of RDRAM PC800
memory along with AGP4X.
The Pentium 4 was introduced along with Intelís 850 chipset, not long ago
it was the only solution available for the Pentium 4; obligating people to
use it without giving them choice to go with an alternative solution.
introduced their 845 chipset earlier this year in order to accommodate their
Pentium 4 with a value segment chip which costs less to produce and eliminating
the need of using the expensive RDRAM memory.
SDRAM PC133 memory was unfortunately the only choice due their agreement with
Rambus stating that Intel was not allowed to produce a non RDRAM chipset supporting
a memory subsystem with a bandwidth higher than 1.06/GB/sec until 2002, limiting
the 845 only to the less powerful SDRAM PC133 memory. Intelís 845/ SDRAM 1.06GB/s
clearly wasnít enough to accommodate the Pentium 4 3.2GB/sec bandwidth, the
845 SDRAM performances was suffering compared to the 850 chip which takes
full use of the 3.2GB/s bandwidth.
Intel had everything planned in advance, knowing and releasing that the 845/SDRAM
would not be the perfect solution for the Pentium 4 due its memory bandwidth
limitation wouldn't be smart, they knew that their competitors were working
on DDR solutions that would offer similar chipsets in terms of features but
with higher potential from its memory subsystem thanks to DDR memory. Intel
was from the beginning designing the 845 to support DDR SDRAM, making the
845/SDRAM a temp solution for the Pentium 4 and giving more time for Intel
to continue working on their DDR support for the 845.
The South Bridge of the 845, ICH2, is the same as in the high end 850 chip
which supports 4 USB 1.1 ports, ATA/100 support, CNR/AMR slots and a 6 channel
ACĒ97 audio along with a LAN interface.
Intelís 845 built on hub architecture is used on the 845 as well. The North Bridge features support for the Pentium 4
processor running at 400MHz Quad Pumped Bus, supports 3GB of memory for PC133
SDRAM or 2GB of PC1600/PC2100 DDR SDRAM along with AGP4X. Note that as Intel
positioned the 845 as a value segment, ECC support is not available on the
The 845D (DDR) and 845 (PC133) versions offer the same features; both share
the same ICH2 hub. The only difference between the 845D (DDR) and the 845
(SDRAM) is the extra support for DDR SDRAM memory on the 845D.