the PCI bus that came from the Northbridge, was used to access the
Southbridge and all the PCI cards via that same bus. This limited the
available bandwidth between the Northbridge and Southbridge.
To address this, the new generation of chipsets used faster, proprietary
busses between the Northbridge and Southbridge. The Southbridge then
got the PCI bridge interface, so all the PCI cards hang off the Southbridge
instead. This can allow faster than PCI speeds when accessing interfaces
contained in the Southbridge.
Mutiol is SIS's proprietary interface between Northbridge and Southbridge.
It has nothing to do with the memory interface.
In terms of options, the 648FX on the P4S800 uses a single channel
memory interface. This can cause problems, like on any chipset, if you
try to drive a board full of memory DIMMs at DDR400 rates. There are
two other SIS chipsets, the 655FX and the 655TX, that support dual
channel. These are on the P4S800D and P4S800D-e respectively. The dual
channels give you two buffered memory interfaces to work with, so it
is easier to drive memory at DDR400 rates, if you don't have as many
loads on the memory bus.
For more info on SIS chipsets, start here:
http://www.sis.com/products/index.htm
Also, visit the forums at abxzone.com and search on the model number
of your motherboard. You can find out whether a board is a dog
or a winner over there.
http://www.abxzone.com/forums/search.php?s=
An early review of a 655TX motherboard is here. I hope this isn't
indicative of how overclockable an SIS chipset is:
http://www.digital-daily.com/motherboard/gigabyte-8s655tx/index05.htm
You can also download the motherboard manuals from the Asus site,
and read before you buy.
http://www.asus.com.tw/support/download/download.aspx
HTH,
Paul