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VX400W enough to power my system? - real beginner here!


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I want to replace my rather average standard spec graphics card for an Nvidia GeForce 8800GT, and having found Corsair's home page, the calculator thingy on there suggested the above PSU, or the VX450W, as being suitable for my setup. It also suggested the 520 I think, but my computer is limited to a 450W max according to HP, so that's out anyway!


Will the cx400w be enough to power my system with stability do you reckon, or am I better going for the vx450w instead? Bare in mind, I'm a student, so price counts, and apart from adding another 2GB of RAM (Corsair of course!), I plan to do no further upgrades to this system, so I need no "headroom" for extras.


Also some of the PSU's I have seen are rated as say, 400watts total output, but have an actual maximum (ceiling) output rated at 405watts. Is this something thats normal with a PSU? I only ask, because I wondered if the vx450w PSU maxed at say 455watts, and my system can only take 450watts (according to HP), will this cause problems?


One other quick question, and any help thats offered will be greatly appreciated, but I wondered if either/both of the PSU's I have discussed are compatible with my microATX motherboard (presumably used to bring the cost and price of the PC down, as opposed to making it small, cos it certainly ain't!)? As far as I can tell from a rough measurement either of the above should fit "physically" in my tower. The current PSU seems to have the same measurements as the Corsair one's, the tower itself is fairly big, and the PSU's appear to have the correct connectors, but I wondered if there would be any other compatibility issues?


One final question, I promise(!), is there anything specific I need to do before installing the new PSU, and once everything is connected (I read the sticky in the forum showing the guide to doing so), and I boot the PC with new PSU installed, is there anything I need to do to set it up, or will the PC "not notice" and boot up as if nothing has changed? I have the latest BIOS settings on the mobo (a word I just learned today!), if that helps.


Thanks in advance for any advice offered, it's a bit of an essay I know, but all I wanted was a new video card, and I now need a new PSU, and a degree in IT apparently.

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The PSU is only going to deliver as much power to the system, as the system requires, so I can not really make any sense of why they would say that you can not use anything with more than 450 watts. The way power supplies are rated is also different from manufacturer to manufacturer so a 450 watt PSU from us, may be equivelent to a 550 watt PSU by someone else's standards.


As for compatibility, your system manufacturer is the only one who will be able to give you a definite answer. Our PSUs are backwards compatible to ATX12v2.01 or newer ATX PSU specifications, and HP normally does not make this information easily accessible to the public. Many OEMs will either use older PSUs which meet older specifications, or they might use proprietary PSUs for their systems, and we have no way to check this information. A lot of newer systems do use standard ATX PSUs so its definitely possible that our PSU would work in your system.


If our PSU Finder recommended the CX400 and you are not planning on any additional upgrades, then I would suspect the CX400 would work just fine for you. After you install the PSU, you should not have to do anything, but if you have any problems, then the first thing I would do would be to reset the BIOS.

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Yeah I thought it was strange that it could be limited like that too, but I reckon they just wanted me to buy HP parts.. or go away! Cheers for your help RAM-GUY, guess getting a new video card isn't going to be quite as easy as I thought, but thanks for your help anyway. Think next time I'm gonna build the PC myself, cos it's pretty pathetic that a shop-bought comp is so complicated to perform simple upgrades on.. at least if your not sure what you're doing anyway!
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