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Intel’s 820 Chipset

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PCQ Bureau
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Motherboard

chipsets are constantly undergoing changes to keep up with increasing CPU

speeds. They’re also getting more feature-rich, and better integrated. The

Intel 820, also known as "Camino", follows the Intel 810 chipset (PC

Quest
January 2000, page 113). Unlike the Intel 810, which had AGP

integrated, the 820 has a separate AGP slot. Furthermore, this AGP bus is

4x, which means that it can support the next generation of graphics cards by

providing a bandwidth of over 1 GB/sec. The 820 also has support for 133 MHz

FSB, and RDRAM (Rambus Dynamic RAM). However, since SDRAM is more widely

available, two motherboard versions are available based on the 820. The

first–CC820–supports only SDRAM, while the other–VC820–supports only

RDRAM. SDRAM support is via a special chip called Memory Translator Hub or

MTH (we’ll talk about this a little later). The 820 can support up to two

PIII processors

Just like the Intel 810, the

820 has been divided into three parts:

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Memory Controller Hub (MCH)

The

MCH is the heart of the system, and links all the major components–processors,

graphics, memory, and I/O–together. It used to be known as the GMCH in the

810, as it had integrated graphics. The MCH is linked to various components

through different buses, which have varying bandwidths. For example, it

talks to the AGP through a 1 GB/sec bus and to RDRAM through a 1.6 GB/sec

bus.

I/O Controller Hub (ICH)

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As can be

seen in the diagram, the ICH talks to all PCI devices through the PCI bus,

to IDE devices like the hard disk and CD drive over the ATA/66 interface, to

external devices over the USB (Universal Serial Bus), and Audio/Modem codecs

via AMR, and finally to the FWH (Firmware Hub). The ATA/66 interface allows

burst transfer rates of up to 66 MB/sec for hard drives. The AMR slot is

meant for connecting a new type of sound card or modem. However, these are

not yet available.

Firmware Hub (FWH)

The firmware

hub (FWH) provides the boot flash memory for the system, which allows

pre-boot management, security, and diagnostic functions. The FWH also

incorporates a hardware RNG (Random Number Generator). This uses thermal

noise inside the chip to produce random circuit transitions. These

transitions are then aggregated and assembled into a random key of any

desired length. A software driver can use this hardware to deliver random

bit streams to security applications.

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Memory Translator Hub (MTH)

The MTH is an

optional add-on chip, which is placed between the MCH and the memory slots,

and allows you to use normal PC100 SDRAM instead of RDRAM. This was not part

of the original 820 chipset design, but was incorporated to make it possible

for 820-based motherboards to be backward compatible with PC100 SDRAM. This

is very useful, as RDRAM is difficult to get hold of and is also more

expensive.

The next chipset on the Intel

block is the 840, primarily aimed at high-end machines.

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