I thought SATA was 150mbps per port, not /4ports, so if you have 4 drives accessing simoultaniously, that each has only a 37.5mbps bandwidth to operate...
ftp://download.intel.com/design/motherbd/bx/D3611001US.pdf
Look at page 28 where it details what SATA chip this board uses.
"As a manufacturing option, the board provides a Silicon Image Sil 3114 Serial ATA (SATA)
controller and four connectors (that support one device per connector) for SATA devices. These connectors are in addition to the four SATA connectors of the ICH7-R/ICH7-DH SATA interface.
The Sil 3114 controller uses the PCI bus for data transfer and provides a maximum data transfer rate of up to 1.5 Gbits/sec."
The controller uses the PCI bus for data transfer, and that gives you 150MB/s bandwidth. Therefore, there are 4 ports on this channel of SATA. So SATA is 150MB/s per SATA Channel, not per port. Every channel can have multiple ports. That is the reason there is a MUX (or multiplexer) in the Seagate white paper. This also makes sense, because no HDD available today that I know of has a burst rate of 150MB/s. Most are in the 50MB/s-80MB/s range. Its a waste, unless you combine 2 or more HDD's in a RAID system.
Even if you had 4 drives on a RAID 0 system on SATA 150MB/s, it would still outperform a single drive since you max out the bandwidth on the SATA bus.
They can tack it on to the PCI bus because the PCI bus runs at 266MB/s these days - depends on the board's clock, 33Mhz or 66Mhz.
P.S. Thats a sweet system!