Netgear against used Atheros hardware for the WNDR4300, like it did for the WNDR3800 and also the WNDR3700. The WNDR4000 had Broadcom chips, however, as did the higher-end WNDR4500. In a way it breaks a trend. Until now the 3000 series had Atheros chips, and the 4000 series Broadcom chips. That distinction can no longer be made.
When you take a closer look at the PCB (see below), you'll notice that the switch is an AR8327. The CPU is an AR9344, that also provides the 2.4 GHz frequency. The AR9380 creates the 5 GHz band. RAM consists of 128 MB Nanya DDR2 memory, an amount that has become standard for routers in this segment.
The antennas are a bit different. Netgear frequently utilises antennas that are part of the motherboard for the 5GHz band. It's an innovation on the part of Netgear, and in our experience provides very good performance. It also saves space, but that doesn't seem to be the main reason Netgear did it this way, since one of the three antennas is placed a distance from the board.
For the 2.4GHz band Netgear also used different antennas. They're Rayspans made from a meta-material that's supposed to perform better than antennas in other materials, while remaining smaller and creating lower SAR values. SAR stands for Specific Absorption Rate, and is an indication for the radiation absorbed by the human body.