But first, let's look at the design details. The NBG318S and PLA450 have essentially the same internal design. Figure 2 shows the inside of the 318S, where you can see the HomePlug AV module that sits above the main board. Under the heatsinks on the module are an Intellon INT6000 HomePlug AV chip and Analog Devices AD9865 Analog Front End. This module looks very similar to the one used in Zyxel's PLA-400 HomePlug AV adapter [reviewed].
Figure 2: NBG318S board with HomePlug AV module
With the HomePlug AV module removed (Figure 3) you can see the Infineon ADM6996 5/6 port 10/100 switch and Atheros AR2318 Single Chip b/g AP router SoC. There is a 16 MB RAM chip mounted under the board. The Flash is probably in the AR2318.
Figure 3: NBG318S board without HomePlug AV module
An alternate loading of the same board is used for the PLA450, which even bears the same FCC ID as the 318S. The main physical difference between the two is that the PLA450 omits three of the RJ45 Ethernet connectors, even though it still has the same ADM6996 switch chip!
One thing definitely worth noting is that both products run pretty hot! I think a heatsink for the Atheros SoC would have been a good hedge against heat-related failures and instability.