The first Intel-based tower Mac, the Mac Pro "Quad Core" 2.66 is powered by two 2.66 GHz dual core Intel Xeon 5150 processors with 4 MB of shared level 2 cache per processor, a 128-bit SSE3 vector engine, and 1.33 GHz "64-bit dual independent frontside buses." Also offered, via custom configuration, were two 2 GHz Dual Core Xeon 5130 processors, two 3 GHz Dual Core Xeon 5160 processors, or starting April 4, 2007, two 3 GHz Quad Core Xeon X5365 (Clovertown) processors.
By default, it was configured with 1.0 GB of 667 MHz DDR2 ECC "fully-buffered" FB-DIMM memory (with a heatsink design that is a bit different from generic FB-DIMMs), a 250 GB (7200 RPM) 3 Gb/s Serial ATA hard drive, a double-layer 16X "SuperDrive", and a NVIDIA GeForce 7300 GT video card with 256 MB of GDDR2 SDRAM, one dual-link DVI port and one single-link DVI port.
Expansion includes two external 5.25" "optical" bays (one occupied by default), four internal 3.5" "cable-free, direct attach" hard drive bays (three free by default), and four PCIe slots (three free with one graphics card installed). Ports include dual Gigabit Ethernet, five USB 2.0 ports, two Firewire "400" ports, two Firewire "800" ports, and optical digital audio in/out, among others. AirPort Extreme (802.11g/n), Bluetooth 2.0+EDR, and a modem are optional.