Will a SLi certified PSU work fine for a Crossfire system

I am building a PC for a friend and he has requested the ADM Spider setup with Crossfire cards.
the graphics card I have selected based on his price range is GV-RX385512H from gigabyte.

He also wants the AMD Phenom 9500 Quad core.
I am looking at the Thermaltake Toughpower 850w - W0131 to power the beast but am unsure if it will work with Crossfire. It is listed as certified for SLi. Does that matter?

Will a smaller PSU suit the quad core and Crossfire setup. Only other things to power will be DVD dual layer burner (SATA), 400Gb SATA 2 HDD, 2x 1gb DDR2 PC6400-800 ram sticks.
Has a few system fans too.

Note this system will be upgraded to 4x1Gb PC8500/1066 eventually and possibly a secondary HDD.
It may also get a different mobo to allow quad crossfire later. I'm still working out the details on that with my friend.
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RartemassLife CoachAsked:
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Gary CaseRetiredCommented:
Sure, it will work fine => the certification simply means it has enough power to handle a pair of modern video cards.
RartemassLife CoachAuthor Commented:
Do you think 850w is too much power, not enough, or just right?
Gary CaseRetiredCommented:
Will a smaller PSU suit the quad core and Crossfire setup => The 3850 is spec'd for a minimum of 550w power supply in Crossfire setups; so Yes, you could use a smaller supply.   I wouldn't "push the envelope" with a minimum capacity unit; but a good 600 or 650w supply would be fine with 4GB of memory and 2 or 3 hard drives.

... but if you're going to upgrade to quad crossfire I'd get as big a power supply as you can !! [Perhaps even a 1KW unit]

A couple of other thoughts ...

=>  If your friend wants 4GB of memory, I'd convince him to go ahead and do that now.   With desktop systems (i.e. unbuffered memory) it's much better to only install 2 modules ... the memory subsystem will be more reliable and, in many cases, faster.   Get a pair of 2GB modules and simply be done with it :-)

=>  If the goal is performance, you should really forget the Phenom and go with an Intel Quad Core system and a motherboard that will support the forthcoming  Nehalem CPU's.    The Intel Core architecture chips are MUCH better than anything AMD makes ... they prove that time-and-time-again in virtually every benchmark.    AMD's new "Phenom" CPU's simply don't come close to the Intel Core 2 based chips ... Maximum PC magazine had this to say in their recent review of the Phenom chips:  "... After all the trash talking, all the 'true quad core' pimping, the result is a chip that's slower than Intel's cheapest quad core.  And more expensive to boot."

... A 1333MHz FSB motherboard (P35 or X38 based) with a Q6600 will beat anything AMD has to offer => and if you pop in one of the faster CPU's (e.g. a QX6850) you'll nearly double the performance !!    Note that X38 based boards also support the forthcoming 1600MHz FSB chips, which are going to include quad cores with hyperthreading (8 logical cores !!).

... and that performance is with the current Intel CPU's.   Next month they'll be shipping the 1600MHz FSB QX9770 :-)   ... and in the fall they'll be shipping Nehalem 45nm chips => which provide direct core-core communications (if their current FSB-based communications chips already blow Phenom away ... just wait until Nehalem !!).

Bottom Line:   If you want top performance, it's a no brainer ... use an Intel-based system.   If you use a 1600MHz capable X38-based motherboard you could more-than-double your already-outstanding performance in the future with a simple CPU-swap once the high-end 45nm CPU's are out and have a few months to drop in price :-)    

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RartemassLife CoachAuthor Commented:
Thanks heaps, I'll pass on the info.
Gary CaseRetiredCommented:
I think I already answered your 2nd question, but since we crossed posts, I'll repeat it:

"... Do you think 850w is too much power, not enough, or just right? " ==> It's more than you need for the system you've specified, but not too much if you plan to upgrade to quad video cards.

... by the way, the Intel system I suggested above won't use any more power than the Phenom => but it will blow it away in performance :-)
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