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:
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)
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.
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.