Just for your information here are the system requirements for the HD 6870 straight from the manufacter site:
http://www.hisdigital.com/un/product2-574.shtml
•PCI Express ® based PC is required with one X16 lane graphics slot with 2 slots space available on the motherboard
•
500 Watt or greater power supply with two 75W 6-pin PCI Express® power connectors recommended (600 Watt and four 6-pin connectors for AMD CrossFireX™ technology in dual mode)
•Certified power supplies are recommended. Refer to
http://ati.amd.com/certifiedPSU for a list of Certified products
•Minimum 1GB of system memory
•Installation software requires CD-ROM drive, a keyboard, a mouse, and a display
•DVD playback requires DVD drive and a DVD
•Blu-ray™ playback requires Blu-ray drive and a Blu-ray disc
•For an AMD CrossFireX™ system, a second AMD Radeon™ HD 6800 Series Graphics card, an AMD CrossFireX™ Ready motherboard and one AMD CrossFireX™ Bridge Interconnect cable is required