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First, I'm a software guy, not a hardware guy. I'm not afraid of hardware, but I don't stay current on the technology. You can probably assume that I know the basics (I know the difference between amps, watts, and volts), but not a lot more.

My teenage son has a Dell Vostro 220s (slimline) desktop. It's a couple of years old now. It came with a 250W power supply, and an Intel G45/G43 Express chipset on the motherboard for graphics.

Now, he's all over powerful video games, and wants a more powerful video card. The game he has in mind requires, at a minimum, an nVidia Geforce 7800 or an ATI Radeon 1800. His display is a Dell 1920x1080 LCD (average quality).

The problem is that, as best I can tell, these cards require at least 350W from the power supply. Most cards video adapters require 400W or 450W. The most powerful power supply I found online (sticking to ones that said they would fit in the chassis) were 300W.

Within 6 months, I will probably get a whole new computer for him. He can't wait.

What's a moderately inexpensive and competent way to upgrade his video adapter? Is there a video adapter that will run with 300W, but has basically the same characteristics as the nVidia or ATI adapters? If he doesn't have lots of slots filled, can we get away with a smaller power supply?

I'm going to encourage him to wait; I'm not looking for parenting advice. But I'd still like to know if there is a way to do this.

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Besides a power consumption limit, that slimline chassis also imposes a GPU card size limit and limited cooling options. There are low-profile GPU cards that do not draw too much power that will fit, but according to reviews, only allow low-frame-rate gaming. They are not expensive ($10 net on sale & after rebate), but the improvement will probably be small. – sawdust Aug 15 '12 at 6:01
I got a votedown?! My question can't be that bad. Are there a few trolls on superuser? That's not cool. – Alan McBee Aug 15 '12 at 17:15
To follow up on why this question was closed, I asked and got answered at meta.superuser.com/questions/5449/… – Alan McBee Aug 22 '12 at 18:28

closed as off topic by MaQleod, 8088, Diogo, techie007, Joe Taylor Aug 15 '12 at 13:32

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1 Answer

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Video cards draw their power off of the 12V rail. There is a sticker on the side of each PSU that lists how many amps are on each rail. Amps * volts = Watts, and maximum power draw for video cards is always listed in watts. Modern CPUs also draw from the 12V rail, and you need to some watts for some other components. I'd assume that a 250 watt PSU won't have more than 12 amps on the 12V rail, probably more like 10. That most likely isn't continuous power either, but peak, which you don't want to sustain, the PSU can be damaged; so if the 12V rail has 150 watts, don't draw 145 at full load. What you'll need to do is see how many amps are on the 12V rail, and what the components will draw, and see if you can safely deliver enough power with the current PSU. The nVidia 7800 GT PCI-E has a max power draw of 85 watts, you'll need to see if his PSU can handle that.

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