In December 2013, Apple released the second-generation Mac Pro with a new cylindrical design. The company said it offered twice the overall performance of the first generation while taking up less than one-eighth the volume. It had up to a 12-core Xeon E5 processor, dual AMD FirePro D series GPUs, PCIe-based flash storage, and an HDMI port. Thunderbolt 2 ports brought updated wired connectivity and support for six Thunderbolt displays. Reviews initially were generally positive, with caveats. Limitations of the cylindrical design prevented Apple from upgrading the second-generation Mac Pro with more powerful hardware.