'MCH' and its Buses
The 82820 chip is named MCH, which stands for 'Memory Controller HUB'. The MCH includes a couple of important buses.
The Memory Bus - 133MHz, 128 Bit = 1.6GB/s
The memory bus in combination with RDRAM is twice that of the BX chipset. However, let's not forget that the CPU can only take advantage of 33% more memory bandwidth, and this is only the case if the CPU runs at 133 MHz FSB. Also, because AGP has moved to 4X it requires increasing the memory bandwidth so it can keep up with the AGP bus. The new RDRAM or Rambus memory does have a much higher bandwidth, but it suffers from higher latencies vs. PC-100 and PC-133 SDRAMs.
The 'Interlink" between the MCH & ICH - 133 MHz, 2x, 8 bit = 266 MB/s
The MCH and ICH are able to directly communicate at 266MB/s. This is much faster than the 440BX's (133MB/s) communication between the North and South Bridge via the PCI-bus.
Right underneath the 'MCH' you can find 82801AA, the 'ICH' = 'I/O Controller Hub'. This part of the chipset talks to all the PCI-devices over the PCI bus, to the EIDE hard drives over the ATA66 interface, to external devices over the USB, to a low priced modem/audio-codec via AMR and finally to the 'FWH' = 'Firmware Hub'. The ICH is the place where all the outside communications run together, forwarded to main memory, the CPU or the AGP graphics controller over this new 266 MB/s bus. You could say that the 'ICH' replaces what used to be called 'South Bridge'.
The FWH - 82802
Behind the name 'FWH' = 'Firmware Hub' you'll find a chip that's not much else than a 4 Mbit EEPROM plus a tiny bit of active silicon. The EEPROM contains the motherboard BIOS and the active silicon is a random number generator. This random number generator, otherwise known as the 'RNG', can supposedly be used by software to provide extra security during computer related transactions (e.g. ECommerce).