eXtreme PSU calculator telling me 575 watts is ok..community says 750W??

[phatazzbp]

Specs:

AMD FX8350
H100i Watercooled
2 sticks 1866 DDR RAM
SLI EVGA GTX 970 ACX 2.0
1 SSD
1 7200 RPM HD
Windows 7 64 bit Home Edition
4 Case Fans(2 LED)
Corsair HX650 PSU
5 USB items(keyboard, mouse, gamepad, Logitech G930 headset, one external HD)

Ive ordered that second GTX 970, but unsure on whether to upgrade the PSU to a 750 or an 850W. Currently the HX850 is cheaper then the HX750 due to rebates, but the Calculator is telling me the HX650 is sufficient. Not sure what to do. Any help would be appreciated.

 

[InvalidError]

The 970s are under 200W each, as is the FX8350 unless you are after some extreme OCing, so 600ish watts sounds correct if you do not mind running the PSU close to full load assuming it can deliver this much power on the 12V rail(s) - I have not looked at the specs. 750W gives you some extra breathing room for aging, momentary peaks, future add-ons and other stuff.

If you can get the 850W model cheaper than the 750W model, that might not be a bad idea.

 

[madmatt30]

Too much conflicting info with the gtx 970s mate
Your cards are capable of pulling 200w+ easily irregardless of the 145w tdp for the 970 stated everywhere.
I reckon your current PSU will power that setup but you're going to be incredibly close to its limits which is never sensible.
I'd be wanting a good 750w PSU personally myself.

 

[Whtwolf]

It is better to have some extra headroom over what the calculator recommends. Go with the 850W and you can add more components in the future without worrying about the PSU.

 

[Barzo]

The community is right, also the HX 850 comes with six 8-pin PCIe power connectors.

 

[juanjostorreshernndez]

Your PSU can power it, but you will be pushing the limits reducing your PSU lifespam. Thas is why all recomend a 700W-750W minimun PSU.
http://www.realhardtechx.com/index_archivos/Page6986.htm
You must also take into acount that your OC specs from AMD use a lot of power, so you need more power in order to do OC activities.

 

[holyrage]

well if ur running sli on a FX that means you are doing some intense OC so yah 750 watts sounds about right IMO if u can get that thing to 5ghz~ than u will have no bottlenecks

 

[Math Geek]

the "community" in this case i highly uninformed!!

your system is pulling 200 watts max if it is highly overclocked. plus the gpu is another 160w for the 970. you're looking at ~360 w total need. that is 30 amps on the 12v rail. you will need about 40 amps to be safe and your psu has 54 amps. you are so far beyond safe it is not even worth worrying about.

let's say the "community" assuming 200w for the 970 is right (which is utter nonsense by the way). that makes 400w power need which is 33.3 amps and roughly a minimum of 42 amps to be safe. you still have 54 amps which is again so much more than needed it is overly safe.

you are fine with that psu and could add more to the system with no worries. believe me i know what "the community" believes and it is not based on any fact or actual math but rather some sort of psu mythology no one actually understands but repeats anyway.

 

[juanjostorreshernndez]

the "community" in this case i highly uninformed!!

your system is pulling 200 watts max if it is highly overclocked. plus the gpu is another 160w for the 970. you're looking at ~360 w total need. that is 30 amps on the 12v rail. you will need about 40 amps to be safe and your psu has 54 amps. you are so far beyond safe it is not even worth worrying about.

let's say the "community" assuming 200w for the 970 is right (which is utter nonsense by the way). that makes 400w power need which is 33.3 amps and roughly a minimum of 42 amps to be safe. you still have 54 amps which is again so much more than needed it is overly safe.

you are fine with that psu and could add more to the system with no worries. believe me i know what "the community" believes and it is not based on any fact or actual math but rather some sort of psu mythology no one actually understands but repeats anyway.

Complete disagree with you, the PSU world is not only maths, you are mising some other things like efficiency and voltage regulation for instance, as your OC specs will put the PSU close to full load, the PSU temps will be high reducing efficiency and maybe some drop close to the limits on voltage regulation wich is 5% from nominal value on that +12v rail, and producing high ripple and noise ratios, that can directly impact on overall sistem stability.
The PSU has better efficiency when is at 50% load, that is why, its recommended higher wats over total comsumption in order to be in that range, and taking into acount some future updates too.
I recommend you to read some articles about PSUs from Hardwaresecrets site for instance.
SO never say community is not based on any fact or actual math but rather some sort of psu mythology no one actually understands but repeats anyway.
cause that is not true.

 

[madmatt30]

I can push my 970 to 230w if I max it out - the low tdp spec by amd is for a reference board & cooler - seeing as EVERY model available is a custom board with custom voltages & power phases that low tdp rating is worthless.
The 970 chipset is capable of running at 140w - there isn't a card available that doesn't use at least 170w minimum though at stock settings at 100% load.

 

[Math Geek]

it's ok to disagree but unless you can show me proof, this still falls under the mythology i speak of. i see power readings for this card oc'ed in an oc'ed i5 and i7 system regularly that does not break 400w. throw all the technical terms out there you wish but in the end there is nothing to back up what you are saying.

i have taken into account effeciency and such with the calculations. note i said "power need which is 33.3 amps and roughly a minimum of 42 amps to be safe" this accounts for only 80% usage. at 400w = 33.3 amps, his 54 amps in a high quality psu is only used at 33.3/54 = 61.6%

i don't care what kind of "effeciency" and such you believe you are considering, but ~62% usage is well withing any safe recommendation based on any real or imaginary specs you can find. show me from anwhere you can find where it states using a quality psu at 62% or less is in any way unsafe and not recommend please

also note that right here on this site every quarter, they do a system build and regularly use this size psu and oc everything and such. you're saying they don't know what they are doing and just get lucky every quarter? http://www.tomshardware.com/reviews/high-end-performance-pc-build,4018-7.html Q3 on the 1600 machine he used a 750w psu for a super power hungry 290x and he measured only 500w used total. this time around with a 980 and everything overclocked he measured 479w which is 40 amps. safe usage is still only 50 amps which this psu could handle fine as well.

the midrange pc used this quarter chose 500w for a i5, gtx 970 system knowing he would oc it as high as possible. again totally clueless or know something you don't?

if 750w is COMPLETELY NECESSARY for the 970 as you say, then why does the 290x which uses 2x the power, not hiccup at all on the same 750w? should that system have NEEDED 1000w to run using you're logic?

i am not trying to berate you but you are simply not correct and we need to spread information that is both useful and correct to those who come here to ask.

 

[madmatt30]

^ aren't we talking about 970sli here ??
Not a single 970
I run a 970 with a oc fx6300 on a 500w which I'm happy with.
I would be dubious about a 8350 (even at stock) with a 970 on less than 550w.
By the same standard I would personally want a minimum 750w for 970sli with an 8350 to allow a little bit of headroom.
650w is really really pushing your luck with a sli setup & an overclocked 8350 IMO.
Will it run it,likely yes but there's a good chance that at some point in time you're going to push it over the limit.

These 3rd party factory over clocked 970's are not particularly low wattage cards in the least ,theyre just well optimised for their comparitive performance/power draw ratio.
The 290x doesn't draw twice as much power but more like 150%.

 

[juanjostorreshernndez]

it's ok to disagree but unless you can show me proof, this still falls under the mythology i speak of. i see power readings for this card oc'ed in an oc'ed i5 and i7 system regularly that does not break 400w. throw all the technical terms out there you wish but in the end there is nothing to back up what you are saying.

i have taken into account effeciency and such with the calculations. note i said "power need which is 33.3 amps and roughly a minimum of 42 amps to be safe" this accounts for only 80% usage. at 400w = 33.3 amps, his 54 amps in a high quality psu is only used at 33.3/54 = 61.6%

i don't care what kind of "effeciency" and such you believe you are considering, but ~62% usage is well withing any safe recommendation based on any real or imaginary specs you can find. show me from anwhere you can find where it states using a quality psu at 62% or less is in any way unsafe and not recommend please

also note that right here on this site every quarter, they do a system build and regularly use this size psu and oc everything and such. you're saying they don't know what they are doing and just get lucky every quarter? http://www.tomshardware.com/reviews/high-end-performance-pc-build,4018-7.html Q3 on the 1600 machine he used a 750w psu for a super power hungry 290x and he measured only 500w used total. this time around with a 980 and everything overclocked he measured 479w which is 40 amps. safe usage is still only 50 amps which this psu could handle fine as well.

the midrange pc used this quarter chose 500w for a i5, gtx 970 system knowing he would oc it as high as possible. again totally clueless or know something you don't?

if 750w is COMPLETELY NECESSARY for the 970 as you say, then why does the 290x which uses 2x the power, not hiccup at all on the same 750w? should that system have NEEDED 1000w to run using you're logic?

i am not trying to berate you but you are simply not correct and we need to spread information that is both useful and correct to those who come here to ask.

REMEMBER is a 970 SLI config in a highly OC AMD rig.

 

[Math Geek]

nice catch matt. my morning coffee is finally kicking in and i do realize now that i missed the part from the op about sli. my apologies to everyone for this glaring mistake so let me rerun the numbers to match this revelation

200w system + 2x 175w 970 (seems to be normal stock wattage) = ~46 amps. 80% usage would be about 58 amps. you have 54 amps, so though the psu will be pulling about 85% of the psu all out. it would work but not recommended to do this for very long even in a quality psu. so it seems you should upgrade that psu a little. look for at least 60 12v amps and you're good. it don't matter if it's 650w or 1000w so long as you cover the minimum amps.

here are 3 that will more than cover your needs http://pcpartpicker.com/parts/compare/evga-power-supply-120g10650xr%2Cevga-power-supply-120g10750xr%2Cxfx-power-supply-pro750wp1750snlb9/


again my bad for missing the sli part. i need to wake up before answering questions.

 

[juanjostorreshernndez]

thats ok.

 

[phatazzbp]

Thanks for the responses and discussion guys. I will go ahead and upgrade the PSU. Do you think it would be alright to run my current setup for a few weeks before I get the new PSU? Or is it not even worth doing at this point?

 

[Math Geek]

all the numbers i used were overestimates to be safe and you're just under recommended needs. you should be ok for a couple weeks but i would upgrade that psu as soon as you can. avoid any oc as well until you upgrade and you should be good to go in the short term.

 

[madmatt30]

Assuming your running oc on the 8350 I would either go back to stock clocks on the CPU for a couple of weeks OR in msi afterburner drop your power limit to 80-85% on both cards temporarily.
& this advice is just to err on the side of caution until you replace your PSU - that should drop your max GPU wattage to 170w apiece max & let's be fair - for those couple o weeks you will still get insane performance from those cards.

Mathsgeek - I did kind of assume you were missing something somewhere mate ;-) from other posts I can see your not a novice so you were confusing me.

 

[Dark Lord of Tech]

You need a decent 750w.

 

[madmatt30]

^ late to the party ;-)

 

[Math Geek]

Mathsgeek - I did kind of assume you were missing something somewhere mate ;-) from other posts I can see your not a novice so you were confusing me.

i was confused as well since i knew you were also not new to the game. then you clarified "sli" and my eyes got wide knowing i had made a mess of things.

at least it got sorted out and the op will be up and running with an insane amount of gpu power!!

 

[InvalidError]

as your OC specs will put the PSU close to full load, the PSU temps will be high reducing efficiency

Wrong cause-to-effect relationship here: while heat does have an effect on PSU efficiency, the main factor affecting it is simply the PSU's performance curve dictated by the design itself and would still be there even if you kept the PSU at a perfectly constant temperature.

When comparing the HX650 with the HX850 at 600W (90% load vs 70%), we are talking 89% efficiency vs 91%, which is only a ~12W difference. Not enough to cause much of a temperature increase in any PSU with a fan in it.

 

[juanjostorreshernndez]

as your OC specs will put the PSU close to full load, the PSU temps will be high reducing efficiency

Wrong cause-to-effect relationship here: while heat does have an effect on PSU efficiency, the main factor affecting it is simply the PSU's performance curve dictated by the design itself and would still be there even if you kept the PSU at a perfectly constant temperature.

When comparing the HX650 with the HX850 at 600W (90% load vs 70%), we are talking 89% efficiency vs 91%, which is only a ~12W difference. Not enough to cause much of a temperature increase in any PSU with a fan in it.

You are right, only 2 degres acording to this review:
http://www.hardwaresecrets.com/article/Corsair-HX650-Gold-Power-Supply-Review/1705/8