No support for Time Machine backup
The WRT1900ACS's USB and eSATA ports can be used to host external storage devices of any capacity. It also supports all popular file systems, including NTFS, HFS+ and FAT32. When a drive is plugged in, you can share its content with other network devices, either via regular file-sharing protocol or through streaming. By default, all clients in your home network can access all the content stored on a connected drive, but you can also turn on secure sharing by user accounts. The router supports UPnP and DNLA streaming standards, meaning content stored on the connected drive can be played back by network media streamers.
Unfortunately, the router doesn't support Time Machine backup, meaning Macs won't be able to use the connected storage device as a Time Machine backup destination. This is quite a big shortcoming considering other routers from Asus and D-Link support this feature.
Other than that, the WRT1900ACS has all the other common features and settings found in high-end routers, such as IPv6, DynDNS, port-forwarding, WPA/WPA2 Wi-Fi encryption methods, and so on.
Great 5GHz Wi-Fi performance
The WRT1900ACS did much better than the WRT1900AC on the 5GHz band. At close range (15 feet or about 4.5 meters), the router averaged 536Mbps, topping the charts of AC1900 routers. When I increased the distance to 100 feet (about 30.5 meters), it now averaged 349Mbps, still one of the best the charts. At this speed, you can transfer a CD's worth of data (700MB) in somewhere between 10 and 20 seconds. For comparison, in these tests, the WRT1900AC scored 523Mbps and 341Mbps for short and long range, respectively.
Also note that at these speed, the WRT1900ACS is a lot faster than even the fastest residential broadband connection. This means it's guaranteed that if you want the fastest Internet speed, this router will definitely help you have the best online experience.
Like its predecessor, the WRT1900ACS wasn't impressive on the 2.4GHz band, either, averaging just 170Mbps at close range and 59Mbps at 100 feet away. However, among the AC1900 crowd, these numbers were among the top two.
While significantly slower than the 5GHz band, the speeds of the router on the 2.4GHz band are still faster than most residential broadband connection. This means, even on this band, the WRT1900ACS is a great router for those with fast Internet connection.
The WRT1900ACS had excellent range about the same as that of the WRT1900AC, up to around 300 feet (nearly 91.5 meters) in my testing. Its effective range which guarantees a stable connection, however, is shorter but still at around 200 feet (61 meters) away. The router passed our stress test with flying colors. During this test it was set to transfer a large amount of data back and forth between multiple Wi-Fi clients on both bands, and it did that for four days in a row without disconnection once.
Note that I tested the router at CNET's offices, where there are walls and many Wi-Fi devices that are out of my control. Generally, walls shorten the reach of a Wi-Fi signal, and other Wi-Fi devices create interference. As with all Wi-Fi routers, your results may vary depending on where you live.
Fast network storage speed
More than a year ago, the WRT1900AC router's network storage performance (when hosting an external hard drive) topped the charts, now the the WRT1900ACS outdid that with a sizable margin.
When hosting an external hard drive on its USB 3.0 port, via a Gigabit connection, it registered the sustained write speed of 97 megabytes per second and the sustained read speed of 108MBps. These numbers were higher even than those of some dedicated NAS servers and the fastest I've seen among routers with network storage capability.
I also noted that the WRT1900ACS stayed quite cool even during extended heavy operation, proving that the omission of the internal fan is a good decision on Linksys' part.
The WRT1900ACS replaces its predecessor, the, as Linksys' best router to date. Among the AC1900 crowd, it's also one of the best in a number of categories, including Wi-Fi speed, range, signal stability and network storage performance.
But at $230 (around £100 or AU$210), it's also among the most expensive routers on the market. Keep in mind that you can get other AC1900 routers such as the, the and even the original for less than $200 and each offers similar performance and features.
That said, if you have a fast broadband connection, one with a download speed of at least 50Mbps, the WRT1900ACS will still make for a great buy. Its long range and fast Wi-Fi speed will deliver Internet to places in your home that other routers might struggle to reach. And the router's fast network storage performance will turn it into a viable network storage solution when you add an external hard drive to it.
On the other hand, if you have a slow Internet connection, spending money on an expensive router generally won't help improve your online experience. In this case, a router of an older Wi-Fi tier, such as the, will get the job done at a much lower price.