For a list of all currently documented Ralink chipsets with specifications, see Ralink.
Manuf/OEM/ODM Alpha Networks WRG-N22
FCC approval date: 19 December 2008
Power: 5 VDC, 2.5 A
Connector type: barrel
)FLA1: 4 MiB
Model?)RAM1: 32 MiB
Expansion IFs: none specified
WI1 chip1: Ralink RT3052
WI1 802dot11 protocols: bgn
WI1 MIMO config: 2x2:2
WI1 antenna connector: U.FL
ETH chip1: Ralink RT3052
Switch: Ralink RT3052
LAN speed: 10/100
LAN ports: 4
WAN speed: 10/100
WAN ports: 1
"8WRGN22..2A10" is silkscreened on the board.
There are multiple 'D' revisions of this router (D1, D2, D3, D4). I don't know what the main differences between units are.
D-Link DIR-615 rev D on TechInfoDepot
On the OpenWrt forums (OUI, boot log, mention of telnet user:pass)
On the DD-WRT forums
DIR-615 series on the OpenWrt wiki