"The benefits of being schooled in the most advanced country in the world are clearly evident when considering our expectations of a graphics setup with two cards. One finger is raised only to be followed by a shy yet determined second, clearly indicating that we should get twice the power with two cards. Common sense however, rarely prevails and that is also the case in this instance. Both SLI and +Fire promise the potential for a 100 per cent increase in performance but due to a variety of restrictions it is unlikely that either will be able to deliver on that potential. "
Quote from megagames.com
What that is saying is due to the GPU overhead of running SLI you won't get exactly 2x performance. You'll get between a 50% to 90% performance increase by adding a second card depending on how well the game's engine takes advantage of SLI/Crossfire. The only time you'd have worse performance in an SLI setup is when the game's engine is poorly coded.
And since your computer is trying to push a second graphics card your temperature inside your cpu increases dramatically, which decreases performance and unless you have a good power supply you will also suffer in performance loss. Not to mention the monster processing unit you will need to get good FPS. If you are using anything but a monster pcu you will see a decrease in performance regarding your FPS.
There are several things wrong with this.
1. Your CPU is always maxxed out when you're playing a 3D game. The engine attempts to use every available clock cycle to render the game/deal with AI, Physics, etc. Adding a second graphics card does not change this.
2. While it is possible for a game to be CPU capped (i.e. the fact that you can't get more FPS is due to your CPU not your GPU power); adding another graphics card does not increase the CPU requirements by any noticeable amounts (all of the SLI/Crossfire communication is handeled over the SLI bridge... the SLI setup appears to be a single graphics card as far as the CPU is concerned).
3. The CPU temperature does not have a direct impact on its performance. Your CPU doesn't magically perform slower as it heats up as long as it stays withing its operational limits. Also if you go back to point 1... the CPU temperature will be the same regardless of your GPU configuration because it will always be running at 100% weather you're running a Voodoo2 or a GTX 280 Tri-SLI rig.
Oh and btw most of the 650 watt power supplys out there are garbage.
What? There are quality power supplies by well known manufacturers from 250w+.
Don't get me wrong I'm not saying that using two video cards in sli or +fire mode would be bad, but let someone like me build your computer, and be ready to empty your bank account.
You can build a decent SLI rig for ~$1000-1200, you don't have to empty your bank account.
i updated to a new Sapphire HD4830 Radeon card, it cost me 200 AUS dollars, i find it tip top, in games and run it in full high grafix, the fan is as big as the cpu fan, apart from having to move the harddrive to another slot due to the card getting in the way of insert,
i know their cards that cost more cash but 200 aus dollars does the job, i researched online for 2 weeks, b4 i went in to ask about it inperson.
the best thing i didnt need a reset. WOOT.
I realize you won't get 100% performance increase, you will only get actually 10-70% on average, sometimes it doesn't even increase at all, however LMK, you where saying on average is decreases, which is wrong. That's all I was pointing out. Having an SLI/CrossFireX setup does not decrease your performance...