Bang goes my idea of sticking one of these in my nforce 650i based board.

Didn't they ever read Ivor Catt?

How about 3 pins per bus, data in, out and clock?

Easy to make the buss tracks all the same length and 400GHz data clock is possible (= 80GBytes / second duplex)

Three pins for 64 bit PCI @ 66MHz is only 4.224GHz clock

MUCH cheaper packages and motherboards.

No reason not to have serial DDR3. It (serial interconnect) was done with PATA/IDE/ATAPI and Wide SCSI.

Admittedly you might need teflon PCB, but two layers (signal/power on top, ground plane on bottom) would do.