sapphire r9 390 - VX550W corsair

Masteryopa

New Member
im here with another hardware forum since I need some more help. I recently upgraded my GPU from a AMD radeon 6950HD to a Sapphire r9 390 8GB.

First thing I read about the 390 is that its very power consuming, recommended by sapphire is a 750W PSU. Though many different reviews and forums suggets that a 550W is enough as long as you dont do any heavy overclocking. During black friday I blindly bought a CX750W corsair and extra 8GB RAM.

After reading a few reviews I got some mixed feelings about it. Many people said its a budget PSU and that many had gotten a defected PSU which might even result in crashing their entire motherboard. Others mentions it makes alot of sound or just works terribly after just a few weeks.

I immedietly regret my purchase, though im slightly uncertain if I can return the item. So my question is. Should I stick with my current PSU(links can be found below), or should I try the budget PSU with 750W?

Current PSU : http://www.newegg.com/Product/Product.aspx?Item=N82E16817139004
New PSU : https://www.komplett.se/product/773...at/corsair-cx-750m-750w-psu#technical-details
(language is swedish if you need to google translate the komplett website words)

Though from a very famous swedish tech website. They tried a complete build with intel core 7, 16GB RAM etc with the 390 and even with overclocking they only managed to reach 490Watt. Without overclocking 410W. So shouldn't my 550W PSU be enough?

Here is the website with the tests :

http://www.sweclockers.com/test/21190-sapphire-radeon-r9-390-nitro/7#content

What do you think? Should my PSU be enough or should I risk using the budget model PSU with 750W?
 

johnb35

Administrator
Staff member
Recommended wattage for that video card is 650 watts. The cx750 will be fine wattage wise, can't say if you'll have other issues with it though.
 

H4rdR3s37

Member
VX550 is enough if you don't have many power hungry parts and PSU is not very old. VX550 is quite old model so it may not be at full shape anymore.

Generally video card "recommended wattages" should always be ignored. Sweclockers article shows why. Personally I have BAD problem, I have only 520W PSU and video card minimum is 600W. I'm so scared :rolleyes:

In any case, if you want better PSU, buy something better than mediocre CX750.
 

C4C

Well-Known Member
VX550 is enough if you don't have many power hungry parts and PSU is not very old. VX550 is quite old model so it may not be at full shape anymore.

Generally video card "recommended wattages" should always be ignored. Sweclockers article shows why. Personally I have BAD problem, I have only 520W PSU and video card minimum is 600W. I'm so scared :rolleyes:

In any case, if you want better PSU, buy something better than mediocre CX750.

I was scared to run my R9 280X on a 600w. I would NEVER run my R9 390 on less than a 600w. Why? Because of headroom and power draw. You want to max at around 80% power usage so your PSU doesn't have to work so hard.
 

H4rdR3s37

Member
I was scared to run my R9 280X on a 600w. I would NEVER run my R9 390 on less than a 600w. Why? Because of headroom and power draw. You want to max at around 80% power usage so your PSU doesn't have to work so hard.

I have never understood that headroom thing. If maximum consumption is at least 100W lower than PSU wattage, there is no need for "headroom". As for power usage, generally PSU works with best effiency around 60-75% of maximum load. So leaving too much headroom would also mean PSU is working outside of best effiency area.
 

C4C

Well-Known Member
I have never understood that headroom thing. If maximum consumption is at least 100W lower than PSU wattage, there is no need for "headroom". As for power usage, generally PSU works with best effiency around 60-75% of maximum load. So leaving too much headroom would also mean PSU is working outside of best effiency area.

Right, so in your case you're overworking your PSU, and thus reducing the life expectancy of it.
Why not go with a recommended product and not risk that? Max TDP for MY build is 509w. That's an 84.8% usage on a 600w psu before fans, HDD's and other power drawing items.

TL;DR

550w is not enough, 600w is alright with a trusted brand/model like a Corsair CX600.
Given your power bill will be higher with a 750w PSU, you aren't hurting anything by having too much power, only too little.
 

H4rdR3s37

Member
Right, so in your case you're overworking your PSU, and thus reducing the life expectancy of it.
Why not go with a recommended product and not risk that? Max TDP for MY build is 509w. That's an 84.8% usage on a 600w psu before fans, HDD's and other power drawing items.

No. I'm optimizing load levels to match load that PSU has highest effiency. There are no valid reasons to leave PSU headroom. That is just myth.

Because that "recommended" wattage has absolutely no use. Basic example:

http://www.geforce.com/hardware/desktop-gpus/geforce-210/specifications

Maximum Graphics Card Power (W) 30.5 W
Minimum System Power Requirement (W) 300 W

So if my rig eats 70 watts without graphics card and 100 watts with graphics card, I need at least 300W PSU :rolleyes:

You can put any recommendation about video card PSU, but it has no use if other components are not known. How can video card manufacturer know what other components you have? It cannot. So recommendations can safely be ignored if better information is available.

550w is not enough, 600w is alright with a trusted brand/model like a Corsair CX600.
Given your power bill will be higher with a 750w PSU, you aren't hurting anything by having too much power, only too little.

550W is enough, but of course it depends other parts. Corsair CX600 is only mediocre quality. Corsair "good quality" is another common myth. Yes, Corsair makes good products but also not so good. And CX600 is not so good.

Using too high power PSU means higher power bill and more expensive PSU. Advantage is what? There are no advantages unless planning to overclock or add more parts later.
 

C4C

Well-Known Member
Please back these claims up.

- Leaving no headroom means your PSU is working at a higher load than it should.
- I've never had a Corsair PSU crap out, and the CX600(M) seems to have amazing reviews and stability.
- You aren't spending that much more for a higher wattage PSU.

I am done arguing over something that seems quite basic. You can always find your true usage using a kill-a-watt meter. If you don't overclock then a 600W is good.
 

johnb35

Administrator
Staff member
Given your power bill will be higher with a 750w PSU
Using too high power PSU means higher power bill

No, that is not true. Your system will only use as much power as it needs. Just because you use a higher wattage power supply doesn't mean your power bill will go up. The bill will be the same no matter if you use a 1000 watt psu or 650 watt psu.
 
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H4rdR3s37

Member
Please back these claims up.

- Leaving no headroom means your PSU is working at a higher load than it should.
- I've never had a Corsair PSU crap out, and the CX600(M) seems to have amazing reviews and stability.
- You aren't spending that much more for a higher wattage PSU.

I am done arguing over something that seems quite basic. You can always find your true usage using a kill-a-watt meter. If you don't overclock then a 600W is good.

- True but leaving too much headroom will lower PSU effiency.
- CX600 is Channel Well Tech made, medium quality not high quality.
- Why spend more anyway? Why buy PSU headroom and gain nothing?

No, that is not true. Your system will only use as much power as it needs. Just because you use a higher wattage power supply doesn't mean your power bill will go up. The bill will be the same no matter if you use a 1000 watt psu or 650 watt psu.

Too much watts on PSU = effiency will be lower = power bill will be higher. Bill will not be same with 1000W and 650W PSU unless effiency is same. And most probably it will not be.
 

H4rdR3s37

Member
Not necessarily. Go read just about any jonnyguru PSU review.

If too many (and I mean way too many) watts, then almost surely. Putting too many watts on PSU will result following:

- Low load effiency is terrible. If computer is on 24/7, that can make lot difference. PSU manufacturers have no real interest improving effiencies under 20% load because 80+ starts from 20%. So going way under 20% usually means very bad effiency and even lower load levels mean terrible.

- Load power is not enough for PSU to achieve optimal effiency.

Both things will mean more power consumption. Taking that 650W vs 1000W PSU in following scenario:

Idle power 60 watts
Typical load (gaming) 400 watts
Absolute maximum load 520 watts

1000W PSU:

Idle power: 6% of PSU maximum
Typical load: 40% of PSU maximum
Absolute maximum load: 52% of PSU maximum

650W PSU:

Idle power: 11% of PSU maximum
Typical load: 61% of PSU maximum
Absolute maximum load: 80% of PSU maximum

Assuming both PSU same quality and general effiency (80+ Bronze for example), 1000W PSU power bill will be much higher because effiency will be lower.

Also worth to remember that 80+ standard requires quite good effiency for 100% load. That means good quality PSU's have not any problems with load levels 10% (or much more) over maximum. So 600W PSU will handle at least 660W without any problems, not 100% on every unit but quite safe assumption.
 

voyagerfan99

Master of Turning Things Off and Back On Again
Staff member
Assuming both PSU same quality and general effiency (80+ Bronze for example), 1000W PSU power bill will be much higher because effiency will be lower.

Reagrdless if you have a 600W PSU or a 6000W PSU if you pull 430W from each of them you're only pulling 430W! That doesn't change! Yes it won't be as efficient on a larger PSU but the change between the two on an electricity bill will be almost nothing.
 

beers

Moderator
Staff member
Both things will mean more power consumption.
You indicated the same point twice.

An easy comparison:

EVGA 650w G2
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=429

EVGA 1600w G2
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story3&reid=391

Differences around ~150w are about 2% in efficiency. Above that the larger unit wins every efficiency test by about the same margin. Even standby loads are more efficient on the larger unit.

But sure, if you wanted a cost analysis:
650wg2 -> 150w 24/7 @ 87% Eff = 172 AC Watts
1600wg2 -> 150w 24/7 @ 85% Eff = 176 AC Watts

At $0.15/kWh you're arguing about $5.26 over an entire year 24/7.

Is it a difference? Okay. Enough to argue incessantly about? Not particularly.


--------------------

This is getting pretty off-topic. The CX750 should do what you want.
 

H4rdR3s37

Member
You indicated the same point twice.

An easy comparison:

EVGA 650w G2
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=429

EVGA 1600w G2
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story3&reid=391

Differences around ~150w are about 2% in efficiency. Above that the larger unit wins every efficiency test by about the same margin. Even standby loads are more efficient on the larger unit.

But sure, if you wanted a cost analysis:
650wg2 -> 150w 24/7 @ 87% Eff = 172 AC Watts
1600wg2 -> 150w 24/7 @ 85% Eff = 176 AC Watts

At $0.15/kWh you're arguing about $5.26 over an entire year 24/7.

Is it a difference? Okay. Enough to argue incessantly about? Not particularly.

Not so easy comparison. That larger unit is much larger and also 3,5 times more expensive. Difference is not much but going to 80+ gold from 80+ bronze makes about same difference. This off topic went out of bounds so for me is fine if we continue with original topic.

As for question, if you can return that CX750, do it and buy better one. I recommend good quality 650W PSU over medium quality 750W like CX750. That old VX550 is probably 5 years old (or even more), replacing it is therefore advisable.
 

Darren

Moderator
Staff member
But sure, if you wanted a cost analysis:
650wg2 -> 150w 24/7 @ 87% Eff = 172 AC Watts
1600wg2 -> 150w 24/7 @ 85% Eff = 176 AC Watts

At $0.15/kWh you're arguing about $5.26 over an entire year 24/7.

Is it a difference? Okay. Enough to argue incessantly about? Not particularly.

This is always my line of thought when people debate power supply efficiency for the sake of cost. Same with power hungry hardware for that matter.

People recommend the CX line for good reason, they're cheap but still of decent quality. Not the best, but for the vast majority of users it's all you'd ever need. I immediately replaced my CX600 that had a dead fan with a CX600M without much thought. It was cheaper than pretty much every other comparable wattage unit at Microcenter. Pretty much every build I do for people I just toss a CX600 in for simplicity's sake and call it a day.
 

Okedokey

Well-Known Member
The difference in headroom and efficiency is cents. Not worth considering. The efficiency between bronze and gold is also false economics, you'll never pay it off.
 
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