Question: Do I Need a New PSU?

[Starbuck1975]

Last summer I built a new rig, but didnt have the budget for a new GPU. Here is my current build, which has been running stable since I built it:

MOBO: ASRock Z68 PRO-3
CPU: Intel x5-2500K
GPU: eVGA GEFORCE 8800GT
MEMORY: 2x4GB Mushkin Enhanced Silverline
OS Drive: OCZ Solid 3 60GB
Back-up Drives: 2xSamsung SpinPoint 1TB
Legacy Drives: 2xLegacy Hard Drives (from my old build)
PSU: ENERMAX Liberty ELT500AWT ATX12V 500W PSU

I am about to upgrade my GPU to either a 560Ti or 6950.

If I run the newegg PSU calculator on my current rig, it tells me I need 542W.
If I run the newegg PSU calculator with the 560Ti, it tells me I need 594W.
If I run the newegg PSU calculator with the 560Ti, it tells me I need 633W.

I guess my current rig is technically over the limit, but seems to be running fine. Given that I will be upgrading my GPU, will I need a new PSU, or can I risk it with my current PSU?

If I do need a new PSU, what would you recommend? 600W? 700W? more?

 

[lehtv]

Your current PSU specs: http://www.enermax.com/home.php?fn=eng/product_a1_1_2&lv0=1&lv1=8&no=22

452W on the +12V rail and two PCIe connectors. At stock your 2500K will consume under 100W, and a 560Ti/6950 consumes ~160-170W... I think you'd be fine with that unit. System load during gaming should be less than 300 watts, or a bit more than 300W if the graphics card and CPU are overclocked moderately. When stress testing the system you might use 400 watts. I would not overclock much just to be on the safe side.

 

[BoomerD]

Most of the PSU calculators are very inaccurate.

If you REALLY want to know...measure your current power consumption from the wall:

http://www.amazon.com/P3-Internation...5625132&sr=8-1

it looks like your PSU is listed at 80+, but for ease of calculation, figure it at 80%.

OR, just accept that Lehtv is right.
(he usually is)

 

[Magic Carpet]

If I do need a new PSU, what would you recommend? 600W? 700W? more?

Generally, you change PSU if

x) you get coil-whine under load
x) not enough / short cables to attach necessary equipment
x) you need more power

I don't think, this is the case here.

 

[Starbuck1975]

I just checked my PSU. I am probably not using the correct technical terms, but since it is a modular PSU, there are 6 black ports and 2 red ports to which I can attach power cables. One of the red female ports has a cable running to my existing GPU. I checked my extra cables, and I have a second red cable. I assume either of the two GPUs I am considering will require both red ports with cables attached? If that is the case, I have both the cables and ports to do so.

What is the worse case scenario if my system places more of a burden on the PSU than it can handle?

To be clear, I am running the CPU, MOBO, 4 hard drives, 1 SSD, an optical DVD-RW and several fans off the PSU.

I don't overclock, so lehtv I will take your advice just to be safe.

My only concern is that the PSU you linked is not the exact one I purchased. I can't seem to find the specs on mine, but here are the details from the invoice:

ENERMAX Liberty ELT500AWT 500W ATX12V SLI Certified CrossFire Ready 80 PLUS Certified Modular Active PFC Power Supply
Item #: N82E16817194003

http://www.newegg.com/Product/Product.aspx?Item=N82E16817194003

 

[Magic Carpet]

Starbuck1975,

Do yourself a favor and buy this. You will be able to measure actual power consumption of just about anything you plug in to a power socket. It's handy.

With regards to "newegg PSU calculator"... just ignore it. It's a power meter for idiots. You will be fine and if not... I can ship you my own PSU, for free ;-P

 

[know of fence]

Currently PSU calculators typically recommend twice your actual max. comsumption, because that's when power supplies hit their maximum efficiency at about 50% load.
The only thing you really risk is losing efficiency on your PSU (bigger power consumption) and a louder power supply fan as you move from 50% load to 100%.
Here's a calc from ASUS just for laughs.
http://support.asus.com/powersupply.aspx

I do agree with Magic Carpet, having a watt meter and maybe even documenting your measurements will definitely ground you in reality. They have the potential to detect major power waste culprits.

 

[currahee440]

Nice rig. Very similar to mine. A lot of people overshoot their requirements for power... but there is far more to it than watts you should know this right? because you bought an enermax PSU!
I suggest you get a new PSU. Newegg shows that the unit can provide up to a maximum of 32A combined on both 12V1 and 12V2.

I looked at a review quickly to see how well the PSU performed. It seems that it was able to push out to 680W but fizzled out a little bit later. The 12V rail was severely undervolted at 10V and the UCP didn't work.

I run a Core i5 2400 (OC'd to 3.6-3.9GHz), GTX 470, 2 DDR3 sticks, 2 SSDs, 4 hard drives, ASUS Xonar DX, a WiFi card, a TV tuner, and an ASUS P8P67LE motherboard and it's well powered by an Antec Neo ECO 520C.

My 520C can handle it because it can provide 40A for 12V. Yours can only handle 32A so I can see this being disastrous if you tried to upgrade. It's not necessarily the card upgrade itself, but rather how many other components need 12V power.

I would say shoot for a 550W-600W unit. Make sure the 12V amperage is around or above 40A and you should be fine.

Update: I have a PSU calculator, it shows that you will use 465W and recommends a 515W unit. For 12A usage it says you will need an estimated 36.2A. Hope this helps. So I would say get a PSU that is higher than 40A.

 

[know of fence]

Bear with me trying to wrap my head around this dark past chapter of PC building.
14 A (170 W TDP reference design) required for Gefore 560ti; 8A (95W) for CPU; 32 A (384 W) available total even with system and drives, still there is plenty -> 10A left for drives and fans. CPU and drives on one rail, GPU on the other.

The only issue I see is that a single rail overheats around 20A. Thus there was a 240VA-DC maximum and rails were separated. (ATX V12 2.2 norm)http://en.wikipedia.org/wiki/Power_supply_unit_(computer)

Enermax says on the sticker, its rails hold 22A (thicker wire?) which is above the 2.2 norm limit for wire overheating, but it should allow for more flexibly when hooking up SATA drives, which can use 3.3V, 5V or 12V.
OP's PSU is indeed ATX12V Ver 2.2" complient according to NewEgg, which would mean that the rails actually are physically separate.
http://www.newegg.com/Product/Produc...82E16817194038 32A on both rails but 22A on a single one, that's the reason why people got rid of this confusion. My completely oblivious guess would be that both red connectors are one split rail. The other rail being the 24 pin connector.

But none of this rail stuff probably matters with todays PSUs since apparently nobody adheres to this 240VA-DC limitation. There is no limits to single rail current at all, rails are only labled as separate. While hungrier cards (like the 560ti) simply have two connectors in parallel.
I wonder if there are any safeties preventing the card from starting up with just one 6pin connector.

ATX12V v2.3
Effective March 2007 and current as of 2011. Recommended efficiency was increased to 80% (with at least 70% required), and the 12 V minimum load requirement was lowered. Higher efficiency generally results in less power consumption (and less waste heat), and the 80% recommendation brings supplies in line with new Energy Star 4.0 mandates.[14] The reduced load requirement allows compatibility with processors that draw very little power during startup.[15] The absolute over-current limit of 240VA per rail was removed, allowing 12V lines to provide more than 20A per rail.

Just trying to figure this stuff out, please correct me if I'm wrong.

 

[lehtv]

My only concern is that the PSU you linked is not the exact one I purchased. I can't seem to find the specs on mine, but here are the details from the invoice:

ENERMAX Liberty ELT500AWT 500W ATX12V SLI Certified CrossFire Ready 80 PLUS Certified Modular Active PFC Power Supply
Item #: N82E16817194003

http://www.newegg.com/Product/Produc...82E16817194003

You're right. I can't find that on Enermax's site. Thankfully the newegg page has a photo of the specs on the side of the PSU, showing 384W on the +12V combined. You'll be fine if you don't OC.

 

[Starbuck1975]

You're right. I can't find that on Enermax's site. Thankfully the newegg page has a photo of the specs on the side of the PSU, showing 384W on the +12V combined. You'll be fine if you don't OC.

Thanks lehtv. I dont overclock, but if ever I feel the need to, that would prompt me to upgrade my PSU.

What about the previous post that mentions my 12V rail is only rated to 32A. I don't understand the implications for what that means, but since you didn't address it, assume it is a non-issue?

Do yourself a favor and buy this. You will be able to measure actual power consumption of just about anything you plug in to a power socket. It's handy.

So this device would allow me to determine how much juice my rig is pulling at different loads?

 

[lehtv]

What about the previous post that mentions my 12V rail is only rated to 32A. I don't understand the implications for what that means, but since you didn't address it, assume it is a non-issue?

Amperes can be converted to watts with the equation Watts = Amperes * Voltage. So it just means the maximum rated capacity of the rail. In this case since you have two +12v rails, 32A (*12V = 384W) refers to the combined capacity of those rails. Each rail individually should be limited to 22A (*12V = 264W), assuming there are functioning protections in place that shut the PSU down if that limit is reached.

So this device would allow me to determine how much juice my rig is pulling at different loads?

Exactly. I own one and it's been pretty interesting and informative to find out how much power my exact build is using in different load scenarios. (You can see the results in the link in my sig.)

 

[Starbuck1975]

Follow up question just so I understand the calculations.

The 12v rail powers the CPU and GPU only correct? My CPU draws 76W idle and 148w at load. A 6950 GPU draws 174W idle and 312W at full load. Won't that exceed the capacity of my 12V rail? How common is it for both to be at full load simultaneously?

 

[Blastman]

Your current PSU specs: http://www.enermax.com/home.php?fn=eng/product_a1_1_2&lv0=1&lv1=8&no=22

452W on the +12V rail and two PCIe connectors. At stock your 2500K will consume under 100W, and a 560Ti/6950 consumes ~160-170W... I think you'd be fine with that unit. System load during gaming should be less than 300 watts, or a bit more than 300W if the graphics card and CPU are overclocked moderately. When stress testing the system you might use 400 watts. I would not overclock much just to be on the safe side.

This.^

Follow up question just so I understand the calculations.

The 12v rail powers the CPU and GPU only correct? My CPU draws 76W idle and 148w at load. A 6950 GPU draws 174W idle and 312W at full load. Won't that exceed the capacity of my 12V rail? How common is it for both to be at full load simultaneously?

Those numbers are way too high. Those PSU calculators tend to way overestimate the power requirements for systems. Also, the CPU/GPU/MB draw some load from the 3.3/5.0 rails, it's just that these days they draw mostly from the 12v.

I did a bit of checking. In this xbitlabs article the i5-2500 drew 106.8w at full CPU load -- and that's including a 6970 that is idling at 20-25w watts. Without a graphics card that i5 will load at well under 100w -- probably ~ 80w.

A 6950 will draw maybe ~ 150-160w tops at full load -- in this test xbitlabs it drew 161.4 while playing Crysis. Sure, you might run some ridiculous OCCT program that can load it a little higher, but under any realistic scenario a 6950 GPU will not come close to loading over 200w.

So lets say 80 + 160 = 240w. Add another 50w for HDD/fans etc, and you will likely not hit over 300 watts with that system. So lehtv's estimates were dead on.:thumbsup:

As an example this guy posted his power usage using a overclocked i7-920 (3.2) and an overclocked 560 Ti. He was using 297w while playing BF3. That system should be a little more power hungry than your setup.

An overclocked i7-3936 (4.3) + 6950 only used 326w while playing Crysis. So, I don't see your system going over 300w.

That 500w Enermax will power your system no problem.