Benchmarking 2.4GHz 802.11n performance
Though you can ostensibly set the router's firmware to forcibly bond two 20MHz channels within the 2.4GHz frequency band to create a single channel with 40MHz of bandwidth, the RT-AC66U automatically backed down to using a single channel when it detected other 2.4GHz wireless networks operating nearby (nevertheless, the router's firmware stubbornly indicated that it was operating a 40-MHz channel).
I assume that this behavior is in preparation for eventual Wi-Fi Alliance certification, since the trade group requires "good-neighbor" behavior of this type, though the Wi-Fi Alliance has not yet implemented a certification program for 802.11ac routers. In my opinion, the router was unnecessarily deferential. My home sits a on a 10-acre lot, and my neighbors' routers are far away. Usually, my network client adapters don't even indicate that the neighboring routers are there at all.
On my 2.4GHz 802.11n benchmark tests, the RT-AC66U performed slightly below the average marks for all five 802.11ac routers, especially at close range (in the bedroom and kitchen tests).
When the distance between the router and the client was greatest, however, the RT-AC66U bested the rest of the field, with the exception of its reference-point cousin, the RT-N66U. In the test charted below, the client and the router were 75 feet apart.
Benchmarking hardwired ethernet performance
The RT-AC66U's four-port gigabit ethernet switch performed as expected, delivering TCP throughput of 943 mbps.
To evaluate the RT-AC66U's performance as a network-attached storage device, I connected a 500GB Western Digital My Passport USB drive to one of the router's USB ports. I used a stopwatch to time how long it took the unit to copy a few files from a PC to the drive over the network (a write test), and then I copied a few files from the USB drive to the networked PC over the network (a read test). The PC was hardwired to the network.
I created a large-file test by ripping a DVD (Quentin Tarantino's From Dusk to Dawn) to the PC's hard drive. Copying this 4.29GB file from the PC to the portable hard drive required 289.7 seconds (about 4 minutes, 50 seconds). This was the fastest time of the five 802.ac routers I tested, but it was slightly slower than the reference RT-N66U 802.11n router. The D-Link and Belkin routers were off the chart here, with scores of 1233 and 2211 seconds, respectively. I couldn't benchmark the Buffalo WZR-D1800H at all on this measure, because the router didn't recognize my NTFS-formatted hard drive.
Surprisingly, the RT-AC66U was slower at copying (reading) the large file from the USB drive than it was at writing to the drive. On the other hand, as the chart below makes clear, the two Asus routers were faster than most of the rest of the field on this measure.
Unless you rip a lot of movies from DVD or Blu-ray discs, you'll rarely move a single large file to a hard drive attached to your router. A more common task is to move batches of small files back and forth across your network. To evaluate each router's performance in this scenario, I created a single folder containing 595MB of small files (subfolders containing music, graphics, photos, documents, spreadsheets, and so on).
On this task, the RT-AC66U delivered the fastest write performance of any of the 802.11ac routers I tested; it was bested only by the Asus 802.11n router I used as a reference point.
When it came to retrieving the batch of small files from an attached hard drive, none of the routers were especially fast. The RT-AC66U took third place, behind the reference RT-N66U router and Netgear's R6300 802.11ac router.
Several of the new 802.11ac routers turned in excellent performance on one test or another, but the Asus RT-AC66U was the best overall. It delivered the top benchmark scores performance on two of my 802.11ac wireless tests, two of my 802.11n wireless tests, and nearly all of my hardwired tests (it was part of a three-way tie for first in this category).
The router is feature-rich, too, with DLNA compatibility for home entertainment use, a built-in iTunes server, an integrated BitTorrent client, and more. And Asus has produced an attractive, user-friendly front-end for tweaking its firmware. I wish that more router manufacturers would follow Asus's example of using external antennas that allow users to fine-tune range and performance.
If you're ready to take the plunge into 802.11ac Draft 2.0 and you don't mind paying top dollar, this is the router to buy.
Note: This review is part of a roundup. Click here to read the introduction to the story and find links to the other 802.11ac routers reviewed at the same time.