when you run multiple vidcards, does that mean you have to run amount of watts the vidcards add up to? example: ATI cards that needs 300w/350w to work (total = 650w). does that mean you need a PSU that's 650w or higher? also, does the same rules apply to SLI/CrossFire systems, or do they work differently?
I believe so... I remember reading somewhere that in order to use 2 x1950xtx in crossfire you need at least a 400 watt PSU. If you're running a big ass card (2 ultras, GTX or 2900XT) then I would recommend something above 600watts. Just make sure that you buy a PSU from a good company (Cooler Master, Antec, Thermaltake, OCZ etc). If you buy from a cheap company, chances are if the PSU is rated at 500 watts then it will get knocked out at 400, or less.
No. The 'recommended power supply rating' is for the whole system and the graphics card. Since all you're adding is another graphics card, not another whole system, the total wattage required only increases by about 100W, since that's how much most graphics cards use. For midrange cards (8600GTS, HD3850), add about 80W, for high power cards (8800GT, X1950 Pro) add about 120W. For the 8800GTX add about 180W, and for the HD2900XT add about 250W. In short: Midrange cards in SLI/Crossfire, you'll want about a 400W PSU. High end cards in SLI/Crossfire, you'll want about a 500W PSU. For 8800GTX in SLI, you'll want a 600W PSU. For HD2900XTs in Crossfire, you'll want a 750W PSU.
now, when you just want to run multiple monitors, no SLI/CrossFire cards; just basic upgrade vidcards and want to get away from integrated graphics, you still need to keep that 100w per card rule, right?
You will need to add 100W to your rated power supply usually, yes. It all depends what PSU you currently have though. If it's a prebuilt system, or if the power supply came with the case, sling it out and upgrade, regardless of what graphics card you install.
cool. now i know to take that precaution when adding additional vidcards. right now i'm just working on improving our gateway gt5458e. threw in pc2-5300 2gig kit, antec 350w basiq, and ati x1550 256 pci-e. all will be replaced on green (not black anymore) friday with pc2-6400 2gig kit, beefier psu (500w+), and nVidia graphics card (so i can finally dual monitor with my integrated graphics). once i get enough money, and stop tinkering with prebuilts, then i'll start doing a full buildup from scratch. but it's hard not to upgrade prebuilts when you can get them for dirt cheap NIB
Out of interest why does it specifically have to be an nvidia card? Just beware, that not any old 500W PSU will do. You'll need a quality unit to do the job.
oh yeah, the lowest i'll go for a psu is an antec unit. my integrated graphics is an nVidia geforce 6150LE. the ATI card won't work in conjuction with the integrated. i can switch the integrated to be always on in the BIOS, but when it boots to windows, a popup will say that it disabled the integrated graphics (code 43). and after doing some research, i found out about the whole ATI/nVidia mixture, and how the drivers won't work with eachother. and i'm not gonna disable one of my cpu cores to make dual monitors work.
Why would you want to do that anyway? Just plug both the monitors into a dedicated graphics card and have done with it.
