[bqq100]

I just got a Asus AC68U and installed DD-WRT, but my laptop with a BCM94352 card will only connect at 400Mbps instead of 866Mbps.

I tried a USB adapter on the laptop and using that adapter it connects at 866Mbps as expected. My phone also connects at 866Mbps.

I tried the following 3 versions and the problem exists in all 3 versions.
DD-WRT v3.0-r28493M std (12/10/15)
DD-WRT v24-sp2 (06/23/14) - build 24461
DD-WRT v24-sp2 (09/13/14) - build 25015M

I also tried restoring the OEM firmware, and with that firmware installed my laptop connects at the 866Mbps as it should.

My settings are as follows:
Channel - 100 [I have tried other channels as well]
Width - VHT(80MHz)
Extension - lower lower
Explicit/Implicit Beamforming - Disabled
Optimize Multicast - Disabled
Advanced settings all on default

I've also tried modifying some of the adapter settings on my laptop, but all with no luck. Short of replacing the BCM94352 with an Intel 7260, I'm at a loss what else to try.

Any other suggestions would be greatly appreciated.

[bqq100]

Finally got it to work, with a really weird quirk...

It connects properly if I use the highest frequency channel for the selected extension( 149: lower lower, 153: lower upper, 157: upper lower, 161: upper upper ). Previously I had tested the various extensions with different channels, but in the 50-100 range.

It's also worth noting that I upgraded to v3.0-r28647 (01/02/16), but I don't think that affected anything.

[Per Yngve Berg]

Your unit is a Broadcom unit, so you should post in the Broadcom Forum.

[Malachi]

Moved.