Is 625 watts enough?

[TheInternal]

Howdy all.

The short:
running a Athlon FX 8320 system with 2-way Geforce 280 GTX SLI on my older 625 watt Enermax Modu82+ PSU. That should be enough power, right?

The Long:
I recently did a partial rebuild on a computer, powered by a 625 Enermax Modu 82+ 625 watt PSU (http://www.newegg.com/Product/Produc...82E16817194027). I'm running into some issues and am trying to eliminate some variables. Namely, the CPU keeps throttling to lower MHz (defective motherboard, maybe?), even at stock settings (despite never going over 45C at 100% load)... and I am getting occasional display driver stopped functioning correctly errors... which MIGHT be due to a defective card, though inadequate power hasn't been ruled out (since I've not got another PSU that I can readily test it with).

The full system:

- AMD Athlon FX 8320 (http://www.newegg.com/Product/Produc...82E16819113285)

- Cooler Master Seidon 120M (http://www.newegg.com/Product/Produc...82E16835103179)

- GIGABYTE GA-990FXA-UD3 rev. 4, BIOS version F2 (http://www.newegg.com/Product/Produc...82E16813128514)

- 2 x EVGA Geforce 280 GTX in SLI (http://www.newegg.com/Product/Produc...82E16814130753)

- 2 x 4 GB Crucial Ballistix 1866 DDR3 RAM (http://www.newegg.com/Product/Produc...82E16820148560)

- Samsung 830 256 GB SSD (http://www.newegg.com/Product/Produc...82E16820147135)

- Western Digital Black 1 TB (http://www.newegg.com/Product/Produc...82E16822136284)

- ENERMAX MODU82+ EMD625AWT 625W ATX12V Ver.2.3 (http://www.newegg.com/Product/Produc...82E16817194027)

- DVD-RW drive

- old Antec P180B case

 

[nwo]

150-200W per card... so yeah, I'd say a 625W would be enough, but it might be cutting it close if you are going to OC anything since you will not have a lot of room for OCing. You could OC CPU or GPUs, but definitely not both. GPUs especially tend to spike in power consumption when OCed, moreso than CPUs.

 

[lehtv]

I would suggest selling the 280's for $50 each and upgrading to a modern card. A single R9 270 or 7870, for example, will perform much better than 280 SLI, use up less power than one 280, and make much less noise. Also it will have more VRAM.

Both load and idle power consumption will go way down. Unless your cost of electricity is high, this upgrade probably won't pay itself back until several years from now (by which time you'd have got rid of the 280's anyway), but it will nevertheless bring back some of the cost.

And to answer your question, it should probably work at stock, but I would not be surprised at all if overclocking the cards (or even the CPU) made the PSU unstable. Have you tried running just one card?

 

[nwo]

I didn't even pay attention to the VRAM, but 512MB VRAM is extremely low most games released in the last couple of years. Heck, even playing Diablo 3 on my 4870 512mb VRAM is choppy at times.

If you play any new demanding games such as BF4, then an upgrade to a 7850 or 7870 with 2GB or VRAM would be advisable to get smooth frame rates at 1080p. I couldn't even smoothly play BF4 on a 1GB 7790 with the settings turned down. Although I was getting 40+ fps, it just felt so much worse and way choppier than it runs on my 7870 2GB.

 

[lehtv]

I didn't even pay attention to the VRAM, but 512MB VRAM is extremely low

The 280's have 1GB of VRAM though

Although I was getting 40+ fps, it just felt so much worse and way choppier than it runs on my 7870 2GB.

That's probably more to do with the fact that the 7870 GPU is 2x faster, than that it has 2x the VRAM

 

[nwo]

The 280's have 1GB of VRAM though



That's probably more to do with the fact that the 7870 GPU is 2x faster, than that it has 2x the VRAM

Sorry I misread the 280s, thought they had 512mb for some reason.

My 7790 has 1GB of VRAM too.

Frame rates did not reflect the 2x performance difference. I have my frame rates capped at 60fps. I get 60fps constant with a 7870 and like I said I get an average of 40-50 fps with my 7790 but it feels extremely choppy.

 

[lehtv]

I have my frame rates capped at 60fps. I get 60fps constant with a 7870 and like I said I get an average of 40-50 fps with my 7790 but it feels extremely choppy.

Well no wonder! If your framerate is locked to 60, you're syncing the framerate with your monitor's refresh rate (either with Vertical Sync or some other framerate cap), which makes it very smooth. Any framerate below that will obviously look horribly choppy in comparison. Personally I don't even bother playing a game at settings that make it go below a minimum framerate of 50.

So the reason for smoother gameplay is NOT the VRAM, it's the higher performance which allows the framerate to be synced to the monitor's refresh rate.

 

[nwo]

Well no wonder! If your framerate is locked to 60, you're syncing the framerate with your monitor's refresh rate (either with Vertical Sync or some other framerate cap), which makes it very smooth. Any framerate below that will obviously look horribly choppy in comparison. Personally I don't even bother playing a game at settings that make it go below a minimum framerate of 50.

So the reason for smoother gameplay is NOT the VRAM, it's the higher performance which allows the framerate to be synced to the monitor's refresh rate.

Ah, that makes a lot of sense now.

Thank you.

 

[Imran60]

I think, 625 watts are not enough to running the system. You should to increase the watts to run the system.