Refurbished Apple Mac Pro 4,1/X5550/12GB RAM/640GB HDD/DVD-RW/B (Early 2009)

The Mac Pro "Eight Core" 2.66 (Early 2009/Nehalem) is powered by two 2.66 GHz Quad Core 45-nm Xeon X5550 (Nehalem) processors with a dedicated 256k of level 2 cache for each core and 8 MB of "fully shared" level 3 cache per processor.

By default, it was configured with 6 GB of 1066 MHz DDR3 ECC SDRAM, a 640 GB (7200 RPM, 16 MB cache) 3Gb/s Serial ATA hard drive, an 18X dual-layer "SuperDrive" and an NVIDIA GeForce GT 120 with 512 MB of GDDR3 memory.

Expansion includes two external 5.25" "optical" bays (one free by default), four internal 3.5" "cable-free, direct attach" hard drive bays (three free by default), and four PCIe 2.0 slots (one free PCIe 2.0 x16 slot and two free PCIe 2.0 x4 slots with the default single graphics card installed).

Ports include five USB 2.0 ports, four Firewire "800" ports, dual Gigabit Ethernet, and both a Mini DisplayPort and a dual-link DVI port, among others. Bluetooth 2.1+EDR is standard, AirPort Extreme (802.11g/n) is optional.

Although the "Early 2009/Nehalem" models look practically the same externally as the "Early 2008" models, there are major technical differences. The 64-bit "Nehalem" architecture is substantially faster and supports "Hyper-Threading" -- which "allows two threads to run simultaneously on each core" (so MacOS X recognizes sixteen "virtual cores" on this model) -- and "Turbo Boost" -- which "automatically boosts the processor speed based on workload" (so if an application is only using one of the eight cores it will automatically increase the speed of the core in use and turn off the unused cores).

It also replaces the frontside bus with a new "QuickPath Interconnect" (QPI) system described as a "bidrectional, point-to-point connection" that provides "quick access to the disk, I/O, and other Mac Pro subsystems".