Both network devices from TrendNET are based on the same main processor. It is a Ralink RT3883F. It has a MIPS core clocked at 500 MHz and incorporates a number of in-built controllers (for RAM, flash memory, USB 2.0, PCI and PCI Express, and Gigabit Ethernet). Most interestingly, it features a dual-band Wi-Fi module working in 3T3R mode which, at least in theory, allows implementing a very fast Wi-Fi. Of course, the hardware components require software support to show their very best.
Notwithstanding its broad capabilities, the processor chip doesn't even have a heatsink for cooling.
The other components are similar between the two devices, too. There is a flash chip for firmware (for 8 MB in the router and 4 MB in the adapter) and a RAM chip (64 and 32 megabytes, respectively). The router employs a Gigabit Ethernet switch Atheros AR8316 for the wired ports whereas the adapter gets along with a Realtek RTL8211CL chip. The router proved not to support Jumbo Frames.
The TEW-691GR’s antennas are attached to the PCB via compact connectors. The TEW-687GA carries its antennas right on its PCB, but they are attached via connectors as well. Each device has a place for a console connector but it is not installed. The router also has bonding pads for a couple of USB connectors.
The hardware components being almost identical, the two devices are likely to deliver high Wi-Fi speed when working together.
The following firmware versions were used in the tests: 22.214.171.124 dated November 2010 for the router (the first update since last May) and 126.96.36.199 dated December 2010 for the adapter (the first and only version available). It raises my apprehensions that the company hasn’t taken the trouble of updating the firmware for several months. Few manufacturers can do everything right at the very first attempt, so the lack of firmware updates may be an indication of the manufacturer's careless attitude towards the products.