Enable 16MB RAM on WRT54GS v5
From DD-WRT Wiki
It is possible to enable the other half of the RAM on a WRT54GS v5 series router running DD-WRT.
nvram set sdram_init=0x0A nvram set sdram_ncdl=0 nvram commit reboot
This action is only valid for WRT54GS v5 routers! mig reported that WRT54GS v5.1 works as well. See His Post