Apple posted, on Thursday, the iMac graphics firmware update 1.0 for 20- and 24-inch aluminum iMacs that have the ATi Radeon HD 2660 Pro graphics card. The update is for those systems running Mac OS X 10.4.10 with the iMac Software Update 1.2.1 or Leopard with iMac Software Update 1.3
Apple said the updates were intended to improve system stability. Installation on an ineligible computer will result in an error message.
Additional details on the update are in Apple support article # 307008.