I have actually seen a 20 pin PSU running a 24pin mainboard system, although i would recommend against it as its under powering the board and could cause instability and possibly hardware damage.
Going a new PSU depends on what GPU you are looking at however the corsair 520's are meant to be good and well liked round these parts i also like antec trio's if you are going for 8800gtx you will want something round the 500-600W mark with some solid quality.
You can buy an adapter to take the 20-pin and turn it into 24-pin. You don't need anymore power then what you already have at the moment, so buying a new PSU wouldn't really be the most economical option until you need the extra power. The adapters are in the range of $2-3, and as with all technology, a better power supply will be cheaper by the time you upgrade to something that needs more power.
Just read your motherboard manual and it will tell you if you can and which pins to use.
I'm in the same situation as you with my mobo and psu and I just plugged the 20 pin connector into the 24 pin socket mobo and it worked!!
But you should probably check the net and your manual first before trying.
thanks for the feedback. The mobo i have is a asus P5K SE board. PSU is thermaltake silent power 480w. What specifically do i need to look for in the manual? I'm not too knowledgeable on power supply details.
I tried to use an Antec 480W with 20-pin connector on a P5B with a 7600GT graphics card, and whilst it booted to windows without problems, any slight stressing of the video card resulted in video corruption and eventually a lock/crash.
Even with a 20-pin to 24-pin cable adapter, I had the same problem.
On other boards (nF4), with a 7800GTX installed, I did not have this problem, and was able to run with this 20-pin PSU (didn't even need the cable adapter).
The extra 4 pins supply additional power to the PCI-e slot, and I believe that it largely depends on how much power draw is required from the PCI-e slot for the graphics card (together with the capabilities of your PSU of course).
If you have a graphics card with a separate power connector, there's a good chance that you will be able to run the system with a PSU that has the 20-pin (or with the cable adapter) as the required power draw required from the PCI-e slot is generally less (my 7800GTX had a separate power connector, whereas the 7600GT did not).
I've been using a 20->24-pin adapter on my current setup for a while now, and I have never had an issue. My powersupply is a 600W single 12v with 37A. You have a 480W single rail with 18A. Although that is much lower spec, the 7600GT shouldn't be all that power hungry. I suppose if you plan on upgrading soon anyway you could go out and buy a new power supply as you will need one in the future, or you could give the adapter a try and see how it works. Oh, I also have used this same power supply with just the 20-pin connected and it works fine also.
Yes it will.As long as the psu has enough amps n the 12volt rail,you should be good to go.In fact one of my systems does exactly that.I'm currently using a 450watt FLOWER PSU,along with a 20 to 24 pin adaptor.So far everything works well.It has a 4400+ X2 cpu as well as a 7800gt and the other usual hardware.Goodluck.I do however reccommend upgrading to a proper psu.
M2N32 SLI DELUXE MB
EVGA 7950GT KO
THERMALTAKE 850WATT PSU
2X1GIG DDR2 800 MEMORY
WD SATA2 80/250GIG HD
RAIDMAX SMILIDON GAMING CASE
XP MEDIA CENTER EDITION
ok well i'm going to try either later tonight or probably tomorrow in putting it all together. if it boots and runs, cool. If not, i'll just go pick up a new power supply. They arent all that much money so it's not that big a deal. another 480-500w psu looks like it'll run me $30-$60
If you do decide to purchase a new PSU - you might want to consider an Antec Earthwatts 500W PSU. I just purchased one online from Frys on sale for $49.99 - NO rebate required - marked down from $89.99. A real deal. The Frys stores in San Jose CA area also have the same special in their stores and you save the shipping - I bought mine online and paid $8 for ground shipping. By the way - this unit is certified to have 80% or better efficiency accross most power ranges.
You might also find this link helpful: Recommended Sub-$150, high-efficiency PSU's
You can buy an adapter to take the 20-pin and turn it into 24-pin. You don't need anymore power then what you already have at the moment, so buying a new PSU wouldn't really be the most economical option until you need the extra power. The adapters are in the range of $2-3, and as with all technology, a better power supply will be cheaper by the time you upgrade to something that needs more power ;^)