This is the kexts for ATI Mobility Radeon HD 550v/4650 (1002_9480), taken from OS X 10.9 (13A603).

Edited by me, works also HDMI & VGA output. Thanks bcc9 & crazybirdy - insanelymac.

Delete only AMD4600Controller.kext.

Install these two kexts with kext utility or others kext installer.

Reboot.

Done !!! source