Apple’s iMac has just received a substantial upgrade in a much smaller package. Announced at the event today in San Jose, Calif., the new iMac is 5mm thin, 80 percent smaller than the previous generation.

Just like the new 13-inch MacBook Pro with Retina display, the iMac is losing its optical drive. All the internal components have been re-enginered, according to Apple’s Phil Schiller.

The 27-inch version has a resolution of 2,560×1,440 while the 21.5-inch iMac has a 1,920×1.080 resolution.

Along with being thinner, the new iMac sheds up to 8 pounds of weight, which is very nice news. Users can have up to 32GB of memory and a 3TB hard drive or 768GB of flash memory.

A third storage option is the new Apple Fusion Drive built-in to Mac OS X Mountain Lion. It’s 128GB of flash storage combined with a 1 or 3TB hard drive. They are both fused together in one logical volume for faster read times.

The standard 21.5-inch iMac will start for $1,299 and be available to ship in November. The 27-inch version starts at $1,799 and will start shipping in December.