From DD-WRT Wiki
 Hardware Info
|CPU Speed||600 MHz|
|Flash ROM||128 MB|
|Radios||1x 2.4 GHz / 1x 5Ghz|
|WLAN Support||A/B/C/G/N AC Draft|
|WLAN Max Speed||450Mbps on 2.4Ghz / 1300Mbps on 5Ghz|
|Antenna Location||6x fixed internal|
|Switch||4x LAN + 1 WAN Gigabit ports|
|USB||1x USB 2.0|
 Flashing Info
This unit has community dd-wrt build support as of 21061.
File needed for flashing dd-wrt from stock firmware:
You should be able to flash the MULTI.bin from within buffalo firmware's webgui. The MULTI.trx file is for upgrading existing dd-wrt installations. Please practice all the proper flashing procedures - hard resetting before and after flashing.
 Links of interest
Here is the forum link for discussion on this particular buffalo unit:
Here is the link to the dd-wrt file server, in which you can use to download newer or older builds.