This time around Shuttle has added on some newer features - USB 2.0 and ATA/133 support is present, as well as the new 533MHz FSB. The new FSB speed allows you to use the newest CPU's and also DDR333 RAM. Combine those features with an onboard AGP slot and you can built one very powerful system in one very small box. We also have firewire and optical in and out on the SS51, as well as the usual Realtek onboard bootable LAN. Returning to the SS51 is the newly named I.C.E. cooling system. This technology uses a heatpipe to cool the CPU so that you can reduce noise by not using a fan on the heatsink, but rather one that blows through a radiator out the back. This allows a lower RPM fan to cool the system quietly, even silently.