From the Apple site
The new power structure.
Engineered around workstation graphics with dual GPUs, PCI Express-based flash storage, high-performance Thunderbolt 2, new-generation Xeon processors, ultrafast memory, and support for 4K video, the new Mac Pro delivers state-of-the-art performance across the board.
Processor.
The new Mac Pro is muscle through and through, starting with the new-generation Intel Xeon E5 chipset. With configurations offering up to 12 cores of processing power, up to 40GB/s of PCI Express gen 3 bandwidth, and 256-bit-wide floating-point instructions, you’ll never be at a loss for speed.
Graphics
Traditionally, pro computers have relied primarily on the CPU for their computing power. But as GPU performance has dramatically increased, software developers have begun to leverage that power in their apps. With the new Mac Pro, we looked ahead and engineered an even more powerful GPU architecture. Not only does it feature a state-of-the-art AMD FirePro workstation-class GPU with up to 6GB of dedicated VRAM — it features two of them. With all that power, you’ll be able to do things like seamlessly edit full-resolution 4K video while simultaneously rendering effects in the background — and still have enough power to connect up to three high-resolution 4K displays.
Storage
There’s flash storage, and then there’s next-generation PCI Express flash storage. We’re talking storage that’s up to 2.5 times faster than the fastest SATA-based solid-state drive and up to 10 times faster than a 7200-rpm SATA hard drive. Most flash storage systems connect via SATA buses designed for slower spinning hard drives. But we designed the new Mac Pro around new PCI Express-based flash controller technology to deliver the fastest solid-state drives available standard in a desktop computer. So booting up, launching apps, even opening massive files happens in, well, a flash.
Expansion, vastly expanded.
In creating a pro computer for the future, we wanted to provide an enormous amount of expansion — without being limited to the space inside the enclosure. Designed with built-in Thunderbolt 2, USB 3, Gigabit Ethernet, and HDMI 1.4 ports, Mac Pro sets a new standard in flexible, high-performance expansion. It’s our most expandable Mac yet. And it has everything you need to build a workstation completely customized to what you need and how you work.