One of the big "tentpole" announcements from Apple’s event this morning was the long-awaited arrival of iMacs with "retina" displays. The flagship 27-inch iMac form factor has been updated with a high-resolution, high-DPI screen, and it's now known as the "iMac with Retina Display." It runs at a resolution of 5120x2880.

The updated iMac with Retina Display keeps the same external form factor as the existing iMacs, so externally, things are unchanged. However, the new internals include an updated LED backlight, an updated oxide TFT display panel, and an updated timing controller to push around the display's 14.7 million pixels.

Apple also says that although the display is brighter and denser than the 27-inch 2560x1440 panel on older 27-inch iMacs, the panel uses 30% less power thanks to the efficient LED design.

The bump in resolution also means more powerful GPUs are required to keep OS X’s visuals operating smoothly. Rumors prior to the event hinted at AMD returning to power the iMacs’ graphics for the first time in many years, and this rumor has proved correct: iMacs now come with Radeon R9 290X or 295X GPUs. The base CPU configuration is a 3.5Ghz Intel i5, which can be upgraded to 4.0Ghz.

High-bandwidth Thunderbolt 2 ports are standard, as is a 1TB Fusion Drive and 8GB of RAM. The base iMac with Retina Display configuration is $2,499, and it will begin shipping today.

One thing we won’t be seeing in the iMac line, at least not yet, is Broadwell. iMacs will continue to use Intel Haswell CPUs for the time being, with the step to Broadwell likely coming in early 2015.

The 21.5-inch iMac has been left out in the cold for now, keeping its 1920x1080 display. It’s possible that the smaller iMac will gain its own retina upgrade when it eventually goes Broadwell.