According to Dell specs http://i.dell.com/sites/content/shared-content/data-sheets/en/Documents/optiplex-990-tech-guide.pdf Page 21, the Small Form Factor Advanced provides 240 Watt.
According to http://www.anandtech.com/show/4263/amds-radeon-hd-6450-uvd3-meets-htpc/13 the Radeon 6450 and 6570 both use only 144 Watt. Which leaves almost 100 Watt left.
So I was thinking why not using a bigger graphic card like 6570 instead? Obviously the first limitation is that it needs also to be a low profile graphic card.
It seems AMD Radeon™ HD 6570 is the next bigger one and still available as Low Profile, which should fit in the OptiPlex 990 (SSF).
1) What I am more interested in is if I could use Cross fire by buying two of these graphic cards and run them on 240Watt? Has anyone tried that?
The wording on AMD Radeon site is not very clear: http://www.amd.com/us/products/desktop/graphics/amd-radeon-hd-6000/hd-6570/Pages/amd-radeon-hd-6570-overview.aspx#3
They claim "The operation of AMD CrossFireX™ technology in dual mode requires a second AMD Radeon™ HD 6670 graphics card and an AMD CrossFireX Ready motherboard. Note that AMD CrossFireX technology in greater than dual mode is not supported with AMD Radeon™ HD 6570 graphics products. "
2) Which makes little sense to me, why do I need a 6670 to run 6570 in a cross fire? Surely I should be able to use the same graphic card for it.
Helpful comments are welcome,
While the 6570 supports crossfire the Optiplex 990 Motherboard IS NOT a AMD CrossFireX Ready motherboard.
AMD CrossFireX™ technology requires an AMD CrossFireX Ready motherboard, an AMD CrossFireX™ Bridge Interconnect
(for each additional graphics card) and may require a specialized power supply.
AMD Radeon™ HD 6570 GPU Feature Summary
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Sorry it seems I had this initially posted in the wrong category. Thanks for correction.
HD 6570 are not support cross fire