Blog by an Apple Certified Tech

Apple has released firmware update for its 27” iMac

The company has released a firmware update for their 27-inch iMacs which is an update for the display hardware itself, which is going to resolved display problems on the new machines. By this update they have reduced blank displays, yellow-tinted LCD colors and display flickering.

iMac smallSo far there are more of positive feedbacks on this launch. Despite these instances, for others the update has worked as expected.
In the knowledgebase about the update, Apple suggests if you continue to experience display flickering issues after the firmware update has been applied, you should check to ensure you have applied the previously released "27-inch iMac Graphics Firmware Update 1.0," which updated the graphics cards on the new systems. So it seems this is a sequel of the old release.

Since these updates and the problems they address have to do with firmware, you might try resetting the system's PRAM and SMC after you have applied the update. Doing this should reset firmware settings and configurations to default values, and clear any potential contributions to the problem by faulty settings. The recent update can be downloaded from the following Web page:
27-inch iMac Display Firmware Update 1.0
If you have not applied the previously released graphics firmware update, it can be found at the following site:
27-inch iMac Graphics Firmware Update 1.0

Hopefully this release will fix all the display issues that iMac 27” users were facing. This was an important step which was expected to be launched early this year.