I just upgraded my routers to TP-Link Archer C7 AC and put an Intel AC 7260 Intel Dual Band Wireless-AC 7260 2x2 Network plus Bluetooth adapter (7260.HMWWB.R) mini-pc wifi card with adapter in my X61. I friggin' love it.https://www.amazon.com/gp/product/B00N7
Note: The above are aparently the same "revised" cards. There are a lot of older versions of the card for sale out there. I searched and bought the revised card for my wife's T61p (coming in the mail) but have the older version AC 7260 HMW installed in my X61 with no problems.
But I had already flashed the BIOS with Middleton's BIOS to remove the whitelist on the X61 years ago to accomodate the 4965AGN-wifi card I had installed in the X61. So, all I had to do to get the X61 working with the AC 7260 was download the drivers from the Intel website (for Windows 10 - which by the way I also love on the X61 and on our two T61p), https://downloadcenter.intel.com/produc
install the AC 7260 mini-pc card with adapter, http://www.ebay.com/itm/262289730083?_t
set up the router's SSID's etc., and renamed my Thinkvantage Access Connections locations to "2.4GHz" and "5GHz" and was good to go. Getting between 144.4 Mbps to ~333 Mbps on 2.4GHz and up to 866 Mbps on 5GHz (of course that is in the local area network, so connection with the internet is still way slow, because I refuse to pay for the high priced high speed internet...)
And success again with the Intel AC 7260 wifi card not only in the X61 last week, but today also in the T61p!
5GHz = 866Mbps baby!!!
2.4GHz = 144.4 Mbps !!!
Interesting happened with the T61p (and this also happened with the X61 with the same card) although after flashing the BIOS I didn't get an 1802 Error code, the card was not recognized, so I went into Device Manager and there it was, and it was acting properly, and when I went to Update Driver it said it already had the best driver. So, I restarted the laptop again and it was recognized and worked fine on 2.4GHz.
But it would not connect on 5GHz. So I went to Thinkvantage Access Connections location profile for my 5GHz and it still had the 4965AGN card in there for the adapter. So I deleted that location profile and then hit Find and found the 5GHZ SSID that the router was sending out and built a new Multi Access Connection location profile around it which automatically recognized the AC 7260 card.
And now all is good.
BTW, I ended up finding that Windows 10 has its own CD/DVD burning software which, once I read 'bout it, was easy to burn Middleton's BIOS update iso image to CD. One thing to remember it will cycle continuously unless you pop the CD out after the machine shuts down before it automatically restarts.