Adding New GPU for Mining

[notaek]

I have been mining for a while, and I have a rig with 4 7970's.  I have another computer that I am going to eventually load up with graphics cards as well, specifically for litecoin.  Right now, I have one 7970 in that computer and the computer is running on a 600w power supply.  My question is, do you think I will have to buy a new power supply before I get a new graphics card?  Which graphics cards might be able to run with a 7970 on a 600w power supply? 

Upgrading the power supply is inevitable, I just want to know if I can add another card before doing so.

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[nethead]

better buy one, since you have money to buy more grafic cards, you will have another 100$ to buy a psu.
Also i would invest in asics right now, exept if you plan on playing games too

[notaek]

better buy one, since you have money to buy more grafic cards, you will have another 100$ to buy a psu.
Also i would invest in asics right now, exept if you plan on playing games too

Yeah, when you put it that way it makes more sense.  I usually buy a new graphics card every 2 weeks or so, and I figured if I could skip the PSU cost now and add a new card in instead, it would boost my overall hash rate sooner.  I am going to stick to GPU's and probably migrate all of them over to litecoin when ASICs drop, so I want to continue upgrading my systems.  What PSU are you talking about that only costs 100$?  All the ones I was looking at that will be able to support 6 graphics cards cost 200 and up.

[ssateneth]

Use a kill-a-watt. Make sure you arent pulling more power than what the power supply is rated for (factoring in inefficiencies). Also make sure to load balance if it's multi-rail. Quality of power supply makes a huge difference too. If it's a no-name, it probably will shut off/explode long before you hit it's rated capacity, or it will send out dirty power (Either too high/too low voltage, very bad ripple, or both). Get a good quality PSU. I have an NZXT HALE90 power supply rated for 750 watts continuous. It draws about 835 watts with 7 GPU's attached to it. It runs 24/7 with absolutely no problems at all. Assuming 88% efficiency, I still have about 15 watts of headroom on it.