I came to this by simple deduction: Other AC cards are working on the 5ghz spectrum. If it is still inside the warranty period (and that card is new enough it very well may be) I would RMA the card and get a new one. Has my card just died? Is there something I'm missing?īased on the description provided (other 5ghz spectrum cards working on same router without issue) I would say that you have either an antenna problem or part of the the chipset in the card went bad. I mean, it should be optimal as both the card and the router are Broadcom based. Those cards connect to the N66U at 300Mb on 5GHz, so I know that works OK. Other AC devices are still working at AC speeds (two Intel 7260 cards, one in a NUC and one in my laptop). I even dug out my old Asus RT-N66U router, fired it up, and the AC card wouldn't even connect to the 5GHz network, and gave a pathetic 16Mb on 2.4GHz. Tried the card in another machine, still 54Mb. I thought Windows 8.1 was being a tart, so I formatted the machine and put Windows 7 on there. I've tried reinstalling the drivers, I've upgraded the drivers. Turns out where I had 720-866Mb links before, I am now firmly stuck at 54Mb. As far as I'm aware, nothing changed, and suddenly playing videos was stuttery, and downloads were slow. It was working fine for about 3 months connecting to my TPLink Archer D7 AC router. It's a PCI-E 1x thing with a massive red heatsink on it, and 3 antennas.

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