Help calculating PSU wattage!

LudoFrancis

Hi All,

I am currently running the below specs;

CPU: AMD FX 8350
GPU: AMD R9 290
MOBO: MSI 970 Gaming
RAM: 32GB X4 Slots
PSU: Corsair CX750M
HDD: 1TB Seagate Barracuda (I will buy a SSD in the future to run alongside this)

CPU Cooler: NZXT Kraken x41 (w/ x1 140mm fan)
Case Fans: x4 140mm
Optical drives: None

Anyway, I want to buy a second graphics card and I wanted to know if I need to upgrade my PSU to a larger wattage to support these cards running in crossfire, which I’m sure I have to do.

If anybody can tell me what would be a safe wattage, that would be great!

truedoom

Went through PC parts picker with your setup (and added the second GPU)

you're running at about 730watts so the 750 watt may not be enough...in theory it should, but can't be sure.

Especially if you are going to add any extra hdd or optical drivers or anything really like that.




Maybe look at a Corsair CX850M instead.

(some of the parts may not be exact in that list, it was the closest I could get )

Xenoronin

I'd say 750 would most likely do. 275W x2 = 550W (Am i correct in looking at TDP for this?)
Then there is the CPU. 125W (some suggest might be closer to 140W running at full tilt) (Same question as above)

675W at max draw leaving 75W to power everything else. Yeah. I think it should just work.
You will most likely never be running CPU and both GPUs at 100% unless you are running some weird benchmarks. If you are looking to overclock that CPU though you might run into issues.

LudoFrancis

Xenoronin wrote: »

I'd say 750 would most likely do. 275W x2 = 550W (Am i correct in looking at TDP for this?)
Then there is the CPU. 125W (some suggest might be closer to 140W running at full tilt) (Same question as above)

675W at max draw leaving 75W to power everything else. Yeah. I think it should just work.
You will most likely never be running CPU and both GPUs at 100% unless you are running some weird benchmarks. If you are looking to overclock that CPU though you might run into issues.

I don't plan on overclocking, but I may add an SSD sometime in the future. Which could take a bit of power.

If both the CPU and GPU run 100% at the same time, would it still work with the 750w? Or should I just upgrade?

LudoFrancis

truedoom wrote: »

Went through PC parts picker with your setup (and added the second GPU)

you're running at about 730watts so the 750 watt may not be enough...in theory it should, but can't be sure.

Especially if you are going to add any extra hdd or optical drivers or anything really like that.




Maybe look at a Corsair CX850M instead.

(some of the parts may not be exact in that list, it was the closest I could get )

Thanks! Still a bit unsure of what to do though

Digital Solitude

750w with a good brand will be enough.

SSDs are extremely low power.

Peak load with an overclocked cpu is about 716w according to http://www.extreme.outervision.com/PSUEngine so a 750w will most likely do the job too, as he adds a 34w buffer

LudoFrancis

Digital Solitude wrote: »

750w with a good brand will be enough.

SSDs are extremely low power.

Peak load with an overclocked cpu is about 716w according to http://www.extreme.outervision.com/PSUEngine so a 750w will most likely do the job too, as he adds a 34w buffer

Thanks for the help!

jonerkinsella

In my current rig I have an i7-3770 (non k) .R9 290 , 8gig ram ,2 ssd ,1 hdd and a Corsair AX1200i . The Corsair psu has a digital watt meter built in . At full wack playing games with a g27 plugged in ...the most the watt meter on the psu registered was 333 watts. Nothing was over clocked manually.

I used to look at the psu wattage calculators , but after seeing what power I was actually consuming... they allow for a hell of a lot of headroom.

Digital Solitude

jonerkinsella wrote: »

In my current rig I have an i7-3770 (non k) .R9 290 , 8gig ram ,2 ssd ,1 hdd and a Corsair AX1200i . The Corsair psu has a digital watt meter built in . At full wack playing games with a g27 plugged in ...the most the watt meter on the psu registered was 333 watts. Nothing was over clocked manually.

I used to look at the psu wattage calculators , but after seeing what power I was actually consuming... they allow for a hell of a lot of headroom.

He's SLIing 290s which is why he needs so much.

The calculators take peak load PSUs into account, which for all purposes are crap but have higher wattage ratings

jonerkinsella

Digital Solitude wrote: »

He's SLIing 290s which is why he needs so much.

The calculators take peak load PSUs into account, which for all purposes are crap but have higher wattage ratings

Yehh...so the 750w should be plenty for him to xfire .

robcon

This review will give you an idea of what to expect when this psu is really pushed.

http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=416

Gumbi

jonerkinsella wrote: »

Yehh...so the 750w should be plenty for him to xfire .

Nah. 8350s suck juice compared to Intel chips, especially overclocked, and a pair of 290s can draw a lot too.


Plus, you want a PSU with headroom for efficiency. 850 at least IMO, esp if overclocking.

..Brian..

I agree. I have (and am currently) run a 3570k and two 290's off a 750w. From what I recall I usually hover around the 650w mark but was getting spikes of up to about 730w being pulled from the wall. This was all at stock voltages so no overclocking.

I upgraded to a 1000w which died unfortunately so I had to RMA it. Haven't gotten around to putting it back in yet.

So I'd say 750w would be OK for stock but if you want to OC I'd puck up an 850. Also I wouldn't want to be running my PSU at like 90 - 95% under load all the time.

Gumbi

..Brian.. wrote: »

I agree. I have (and am currently) run a 3570k and two 290's off a 750w. From what I recall I usually hover around the 650w mark but was getting spikes of up to about 730w being pulled from the wall. This was all at stock voltages so no overclocking.

I upgraded to a 1000w which died unfortunately so I had to RMA it. Haven't gotten around to putting it back in yet.

So I'd say 750w would be OK for stock but if you want to OC I'd puck up an 850. Also I wouldn't want to be running my PSU at like 90 - 95% under load all the time.

Difference is, an 8350 sucks juice compared to a 3570k. A LOT more. So I'd definitely say get 850 minimum.

LudoFrancis

Gumbi wrote: »

Difference is, an 8350 sucks juice compared to a 3570k. A LOT more. So I'd definitely say get 850 minimum.

I think I might just have to do so!

Serephucus

..Brian.. wrote: »

I agree. I have (and am currently) run a 3570k and two 290's off a 750w. From what I recall I usually hover around the 650w mark but was getting spikes of up to about 730w being pulled from the wall. This was all at stock voltages so no overclocking.

This means your 750W PSU is only pulling about 650W max. Worth bearing in mind.

..Brian..

Hold on, is it not the other way around? If the power monitor shows 730w being pulled from the wall, isn't the PSU producing about 600w at 80% efficiency?

Serephucus

Yeah, bad wording on my part. I should have said there's around 600W being pushed to the machine or something.

..Brian..

Haha yeah I was scratching my head there for a sec! The PSU still needs to be able to handle all that power though so I'd still recommend 850w especially with a AMD cpu.