Is my PSU holding me back 285GTX i7 920

[villan]

I have a cooler master eXtreme Power Plus 550W with a power rate of DC output +3.3v/25A, +5v/25A, +12.1/16A, +12v2/16A, -5v/0.8A, -12V/0.8A 5Vsb/2.5A. i7 920 OC 3.6Ghz gainward 285GTX OC 700Mgz.
I find that i get slow FPS in FSX about 15fps over new york city maxed out. Yet if i run 7800GTX 256meg x2 Sli im getting better FPS using 182.06 drivers vista 64 6Gb ram.
The 7800GTX cards have given me way better FPS no matter were i fly. I have run the 285 on a 2nd PSU with 1 and 2 power connectors with no change in performance

 

[pat mcgroin]

Are you running the DX10 preview on one card and not the other?
That would have a pretty big effect on the frame rates.

Below is a link for the power requirements for a 8800gtx.
I would think that they are similar for your card.

http://nvidia.custhelp.com/cgi-bin/nvidia.cfg/php/enduser/std_adp.php?p_faqid=2003&p_created=1166607492&p_sid=dfMthm_i&p_accessibility=0&p_redirect=&p_lva=&p_sp=cF9zcmNoPTEmcF9zb3J0X2J5PSZwX2dyaWRzb3J0PSZwX3Jvd19jbnQ9MTUsMTUmcF9wcm9kcz0yJnBfY2F0cz01OCZwX3B2PTEuMiZwX2N2PTEuNTgmcF9zZWFyY2hfdHlwZT1hbnN3ZXJzLnNlYXJjaF9ubCZwX3BhZ2U9MSZwX3NlYXJjaF90ZXh0PXBvd2Vy&p_li=&p_topview=1