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Problems from "under powering" graphics card?

S

sgweber

n00b
Joined
Sep 2, 2008
Messages
1
I currently have a SFF Shuttle system with a 350W silent X PSU.

I recently purchased a Diamond Radeon HD4850 video card, which requires a 6 pin PCI-E power connector. In order to power the card I bought a converter cable to conver two 4-pin molex to a 6-pin PCI-E. The connector wants 2 molex connectors, one using 3 of the 4 pins, the other using 2 of the 4 pins.

The kicker is I only have one molex connector available on my PSU, since I want to keep using my CD-drive. So to keep this functionality I plugged my last available molex connector to the part of the converter that wanted 3 of the 4 pins.

The card powered up just fine and I am able to game effectively. Also, the point will be moot in a week or 2 when I get my new 450W PSU, which has a PCI-E connector on it.

However, out of curiosity's sake I am wondering what, if any, the possible problems could be from "under powering" my graphics card?
 
Google search of 4850 PSU requirements showed this on first hit:

ATI Radeon HD 4850 System Requirements:
o 450 Watt or greater power supply with 75 Watt 6-pin PCI Express® power connector recommended (550 Watt and two 6-pin connectors for ATI CrossFireX™ technology in dual mode).

Although this is for total system power, its good that you are upgrading your PSU very soon.

One gripe I have with all the video card manufacturers is that they give this 'total system' PSU requirement. What they should give is exactly max current draw on what voltage line e.g. 10amps from 12v source. That way we could work out balancing etc. rather than guess work.
 
I'm all for the amp measurements and usually you can probably get some educated guesses from power consumption measurements in reviews. However, the chip and card makers probably don't trust the average consumer knowing how each PSU is set up by the rails. Wattage is a safety net where they can say basically most 450W or w/e power supplys abiding by certain ATX standards will run the cards.

to OP: if you can tell us the config of your shuttle box and the amount of amps on the 12V rail on the PSU, we might be able to give a more concrete conclusion. Though as a pure guess, I'm going to say that 350W probably would've been at 80%+ load during gaming, which isn't the best conditions for a PSU.
 
The lines can no doubt handle the power, that's not the case. My only question would be what are the consequences of NOT sending power to all the connectors on the card (mainly because I don't know the circuitry of the card that well). You could split the last molex connector with a Molex Y-Cable, so that you could send power to all the lines in the connector. Still though, it'd be a good idea to check out the exact specifications on your PSU before you try running the rig. It'd suck to get a new card in there and then have the PSU fry your whole system :eek:.
 
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