ASUS RT-AC88U Dual-Band Wireless-AC3100 Gigabit Router Reviewed

Introduction

ASUS has gone all-in with Broadcom for its second try at 4x4 routers, with three models. The $400 MSRP for the top-of-line AC5300 class "tri-band" RT-AC5300 is testing the limits of Wi-Fi router buyers' willingness to throw money at the hope of better performance. The AC3100 class RT-AC3100 has the normal one radio each for 2.4 and 5 GHz and comes with a more reasonable $280 list price.

Finally, the AC3100 class RT-AC88U, which is the focus of today's review, asks only a $20 premium over the RT-AC3100 for the benefit of four additional Gigabit LAN ports (and some snazzy red accents for gamer bait).

The AC88U's body footprint is only slightly larger than the AC87U's. But it will require about 4" more of width on your shelf or table (approx. 15.5" vs. 11.5") because of the move of two antennas from rear to side.

The AC88U's more angular styling succeeds in projecting a more aggressive image. But it also has a practical benefit of better ventilation. The top-side airflow through the large top grille positioned right over the internal heatsink is supplemented with smaller air-scoops lined up with the row of indicator lights and on the front edge. There are also vents along the top rear panel above the connectors. Bottom-side ventilation is very good, too, with the bottom cover full of ventilation slots.

The bottom also has two mounting screw slots revealed by removing their rubber plugs. The slots are toward the rear, which will point the connectors up if you hang the router on a wall.

The callout graphic below shows all the ports, indicators and switches. Other reviewers have applauded the indicator lights' move to the top cover and I do, too. Now you can see them without ducking down or lifting up the front of the router.

Inside

The NETGEAR R8500 review contains all the background on Broadcom's 4x4 architecture, so I won't repeat it here. In sum, the RT-AC88U and its alternate versions are dual-band 4x4 AC3100 class routers using Broadcom's first 4x4 chipset. Although the BCM4366 4x4 radio is MU-MIMO capable, the AC88U does not currently support MU-MIMO.

The 3100 in AC3100 comes from:

1000 Mbps (2.4 GHz) + 2165 Mbps (5 GHz) = 3165 Mbps

Since AC3200 is already used by 3x3 three-radio (aka "tri-band") routers, manufacturers wisely rounded down to AC3100 to avoid confusion.

The disclaimer on the AC88U's product page says "MU-MIMO beta firmware will be available by the end of 2015". I asked my ASUS contact about this and received this reply forwarded from ASUS HQ:

MU-MIMO firmware will be put on support site in few days. This firmware will be marked as alpha firmware for MU-MIMO and add the limitations in release note.

If ASUS comes through, the RT-AC88U will be the first of the Broadcom 4x4 routers to get its MU-MIMO wings.

Table 1 summarizes the key components of the ASUS RT-AC88U and includes the NETGEAR R8500 for comparison. Note the R8500 has two 5 GHz radios. Also note BCM4709C0KFEBG = BCM47094.

	ASUS RT-AC88U	NETGEAR R8500
CPU	Broadcom BCM4709C0KFEBG dual-core @ 1.4 GHz	Broadcom BCM4709C0KFEBG dual-core @ 1.4 GHz
Switch	4 ports in BCM4709C0KFEBG + four ports in Realtek RTL8365MB	in BCM4709C0KFEBG & BCM53125
RAM	512 MB	512 MB
Flash	128 MB	128 MB
2.4 GHZ Radio	- BCM4366 4x4 2.4/5G single chip 802.11ac SoC - Skyworks SE2623L 2.4 GHz power amp (x4) - Skyworks SKY85201-11 2.4 GHz SPDT switch w/ LNA (x4)	- BCM4366 4x4 2.4/5G single chip 802.11ac SoC - Skyworks SE2623L 2.4 GHz power amp (x4)
5 GHz Radio	- BCM4366 4x4 2.4/5G single chip 802.11ac SoC - RFMD RFPA5542 5 GHz PA module (x4) - Skyworks SKY85605-11 5 GHz SPDT switch w/ LNA (x4)	- BCM4366 4x4 2.4/5G single chip 802.11ac SoC - RFMD RFPA5542 5 GHz PA module (x4)

Table 1: Key components summary and comparison

The RT-AC88U, RT-AC88R and RT-AC3100 all share the same FCC ID (MSQ-RTGW00), so must have the same Wi-Fi performance characteristics. As noted previously, the only difference between the AC88 and AC3100 is the number of LAN ports. The way this is done is LAN ports 1 - 4 come from the Broadcom BCM4709C0KFEBG's internal Gigabit switch. The 88U/R ports 5 - 8 are supplied by a Realtek RTL8365MB Layer 2 Managed 4+1-Port 10/100/1000M Switch Controller on the bottom of the board.

The AC88U gets snazzy red heatsinks to match the red insets on its four antennas. I don't know why ASUS bothered, because the heatsink is barely visible through the top cover grille. The FCC photos are kind of fuzzy, so I took the shot below when I opened up one of the samples after testing.

I went all the way and removed the heatsinks and RF can tops to identify the RF amplifiers. As we've seen in other designs, the 5 GHz and 2.4 GHz amplifier and associated switche sections are interleaved. The BCM4366 on the left is the 5 GHz radio; 2.4 GHz is to the right.

Here's an FCC photo of the board bottom side with 128 MB of flash and the Realtek switch.

SUS filed a Class II permissive change in November that made the changes shown below. I confirmed the highlighted increase in RAM was present in the samples ASUS sent.