AMD Graphics cards by default, like most hardware, has an energy saver mode enabled. This works especially well with crossfire builds. Use the follow code as a preview or to copy and paste or Download The Registry File I made instead.
Windows Registry Editor Version 5.00
;disable amd catalyst ulps power saver mode for video cards
[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\{4D36E968-E325-11CE-BFC1-08002BE10318}\0000]
"EnableUlps"=dword:00000000