The AMD FirePro W8000 and FirePro W9000 are nearly identical cards as the share the same PCB, GPU Cooler, and backplate, as well as a derivative of the Tahiti GPU.
Both cards are 11-inches in length and stand nearly 4.25″ tall. The old AMD FirePro V8800 was only 10.5″ long, so these cards are half an inch longer.
The first major difference between the AMD FirePro W8000 and W9000 are the PCIe power connectors. The AMD FirePro needs both an 8-pin and 6-pin PCIe power connector. The AMD FirePro W8000 uses less power and therefor can get away with just a pair of 6-pin PCIe power connectors.
The next major difference is the video outputs. The AMD FirePro W9000 professional graphics card has six mini DisplayPort connectors. With this configuration you can drive up to six displays with AMD
Eyefinity technology without the need of DisplayPort 1.2
multistreaming technology. The card also has a
stereoscopic 3-pin mini DIN for AMD HD3D Pro (stereo 3D). The exhaust port from the GPU cooler is still fairly large considering all the connectors located on the card.
The AMD FirePro W8000 has four standard DisplayPort video connections. With this configuration you can drive up to four displays with AMD Eyefinity technology, and up to six utilizing DisplayPort 1.2 multistreaming technology. AMD HD3D Pro is supported with the stereoscopic 3-pin mini DIN.
Both the AMD FirePro W8000 and W9000 can operate at resolutions well beyond standard HD, at a max of 4096×2160, due to DisplayPort 1.2 support (Max DisplayPort 1.1 Resolution: 2560×1600). Bring on the 4K monitors!
Both cards have the pair of AMD CrossFireX interconnects, so multi-GPU setups are allowed.
You also have the connector that facilitates synchronization to external sources (Genlock) or synchronizes 3D rendering across multiple GPUs in different systems (Framelock). Addition add-in cards like the ATI FirePro S400 can be used to ensure clock-accurate synchronization.