The Power Macintosh G5 "Quad Core" (2.5), was the first and last Power Macintosh G5 models to use dual core PowerPC 970MP (G5) processors, which have two independent processor "cores" on a single silicon chip. The Power Macintosh G5 "Quad Core" (2.5) is powered by two "dual core" 2.5 GHz PowerPC 970MP (G5) processors with four optimized AltiVec "Velocity Engine" vector processing units (one per core), eight double-precision FPUs (two per core), 1 MB of on-chip level 2 cache on each core, and dual bidirectional 1.25 GHz frontside system buses (one for each processor). It shipped configured with 2048 MB of 533 MHz PC2-4200 DDR2 SDRAM, a 250 GB (7200 RPM) Serial ATA hard drive, a 16X dual-layer "SuperDrive", and a NVIDIA GeForce 6600 video card with 256 MB of GDDR SDRAM. Connectivity includes USB 2.0, FireWire "400" and "800", a single-link DVI and a dual-link DVI port, optical digital audio in/out, two independent Gigabit Ethernet ports, and support for AirPort Extreme (802.11g) and Bluetooth 2.0+EDR. Power Macintosh G5 models have three open PCI-Express (PCIe) expansion slots. The Power Macintosh G5 "Quad Core" (2.5) uses the same easy-to-upgrade "anodized aluminum alloy" case as all other Power Macintosh G5 models with the same removable side panel for easy access to internal components. Likewise, it is divided into four different thermal zones with nine computer-controlled fans for optimum cooling.