|At a Glance|
|Product||D-Link Xtreme N Duo Wireless Media Router (DIR-855)|
|Summary||Dual-band dual radio Wi-Fi Certified 802.11n Draft 2.0 router based on Atheros XSPAN silicon|
|Pros|| Two radios for simultaneous dual-band operation
Gigabit WAN and LAN with > 300 Mbps routing speed
High simultaneous sessions
Automatic QoS for Internet uplink and WLAN
Lacks of matching adapter holds back performance
Finally, the review that dual-band draft 11n fanboys and girls have been waiting for: D-Link's DIR-855. Since the 855 uses the same main board as its DGL-4500 dual-band single-radio sibling, please go over to that review if you need details on the 855's feature set. I'm going to cover only the differences here—which are in the wireless configuration—and concentrate on how it performed.
As I've said before, the 855 is the DGL-4500 loaded up with two radio boards instead of one. So it has the same OLED front panel, same rear panel connectors and same feature set. The only difference is that the 855's case and antennas are white, to better appeal to homebodies (vs. black for gamers).
Unlike the Linksys WRT350N [reviewed] and WRT600N [reviewed], the USB port on the back isn't used to attach a drive for sharing a USB drive or printer to your LAN. It's just there to support the flash-key based Windows Connect Now (WCN) auto-configuration method. Note that all three antennas use RP-SMA connectors for easy upgrade, if you can find dual-band antennas!
Figure 1 shows the 855's main board and Figure 2, the 4500's. There actually is a difference, hidden under one of the 855's heatsinks. The 855 uses a Ubicom IP5170, clocked at 350 MHz, while the 4500 uses a Ubicom IP5160, clocked at 275 MHz. You'll see the difference that this makes in routing throughput shortly.
Figure 1: DIR-855 main board
The gigabit switch however, is a Realtek RTL8356, instead of the Vitesse VSC7385 used on the DIR-655. The Realtek switch chip supports up to 9K jumbo frames, and I found that it handled 4K jumbo frames just fine. D-Link still doesn't spec jumbo frame support.
Figure 2: DGL-4500 main board
Although both radios use Atheros XSPAN chipsets, they are not the same board. The 2.4 GHz radio (Figure 3) uses the Atheros XSPAN AR5008 chipset, with AR5416 Baseband/MAC and AR2133 3 Tx, 3 Rx, single-band 2.4 GHz chips.
Figure 3: 2.4 GHz radio board
The 5 GHz radio (Figure 4) is the same one used on the DGL-4500. It uses the same AR5416 Baseband/MAC, but the AR5133 3 Tx, 3 Rx, dual-band 2.4/5GHz radio, instead of the AR2133.