The D51S comes with an Intel Atom dual-core D510 processor on board which supports hyper-threading and has an integrated memory controller. This allows for the use of dual-channel DDR2 memory. The board can take a maximum of 4GB of memory, either DDR2-667 or DDR2-800.
The chipset is the Intel GM10 which does not cater for a PCI-e bus. There is one PCI expansion slot on board.
There are no IDE and floppy controllers. Two SATA-II slots are available and the board helpfully comes with SATA cables; one is much shorter than the other, the manufacturer having assumed that one will only use the board in a mini-ITX case.
Had two regular size cables (12") been provided it would have been better; the shorter (6") of the two did not prove of any use to me in this case. This is about the only fault I could find with this board.
It took me about 20 minutes to install the latest Debian release (Lenny) with 2GB of memory on board. Very snappy and it runs quiet too.