0.30 V drop only on +5V rail during Prime95 - Is this normal?

I ran into a strange problem with Prime95 on a previously completely stable 3.60 GHz overclock speed after adding in a Scythe S-Flex 1,200RPM 120mm fan. Previously I did multiple 9+ to 11+ hour stress tests on the same settings and got a clean results but yesterday my computer blue screened. I disconnected the fan but the power issue is still the same so the fan is not the cause, just the reason why I noticed the power problem on the +5 V rail in the first place.

I inspected the fan and it draws power from the hot yellow +12 V rail line and returns it properly to the black neutral line right next to the yellow and I don't see any resistor packs on the lines so it doesn't seem to include a undervolt mod on the lines from the factory.

POW: OCZ PowerStream 520W SLI ADJ ATX2.0 EPS12, +3.3V 28A, +5V 40A, +12V 33A

I decided to look at possible power supply issues and noticed that previously my system's +5 V rail was running at +5.07 V and it would dip to ~4.72 V during Prime95 Blend within about a minute or two. I have an adjustable power supply so I used the potentiometer to up that rails' voltage to ~5.21 V and now it drops to +4.85 V after a minute and dips occasionally to +4.83 V after a few minutes of running it. I can't push my rail any higher or the green LED on the power supply turns read indicating that it is out of range and then Asus Probe II will also shown a warning. Still the +3.3 V does not change and +12 V drops only 0.05 V during Prime95 stress testing.



Now is this type of a drop normal for my power supply?

Below is the thread that I'm using as a working log of the overclocking issues with my computer.

[H]ard|Forum > [H]ard|Ware > Overclocking & Cooling
Overclocking Air: Intel i7 920, Asus P6T, G.Skill DDR3-1600 C8, Xigmatek HDT-1284E



Below is my current system config for reference.

[size=-2]
MOB: ASUS P6T, LGA 1366, Intel X58 ICH10R, 3 SLI, 6 DIMM, 6 SATA - FW: 0603, AiTweaker XMP, Turbo Off, HT On, SpeedStep On, C-Step On, (Settings) Auto
CPU: Intel Core i7 920, 2.66 GHz, 4C, 8 MB, 4.80 GT/s QPI, 45nm, 130 W, D0 (SLBEJ) 3901A238 - 3.60 GHz, BCLK 180, Multi 20, CPU 1.20 V (Manual), QPI 1.21250 (Auto)
FAN: Xigmatek HDT-1284EE 120mm Hydro Bearing Fan 800-1500 RPM 4 Heatpipes - 41 C Idle, 81 C Load
RAM: G.Skill 6gb (3 x 2 GB) DDR3 1600 (PC3 12800) 8-8-8-21 2T 1.60 V - XMP Profile 1, Ratio 2:8, Frequency 720 MHz (1,440 MHz), DRAM 1.60 V

VID: eVGA nVidia GTX 260 896 MB G92 192c 576/999 MHz PCI-e 2.0 16x 2xDVI 1xSVid 1xHDTV - 600/1100 MHz, DVI to LCD, HDMI 60' to 50" Plasma TV.
CAP: AverMedia AVerTV Combo PCI-e M780R ATSC/NTSC Capture MPEG-2 Hardware Encoder - MCE Remote, IR Receiver

CAS: Lian-Li PC-V1200 Plus Mid-ATX Aluminum 4x5.25 6x3.5 2x120mm - Best case to date in my opinion.
POW: OCZ PowerStream 520W SLI ADJ ATX2.0 EPS12, +3.3V 28A, +5V 40A, +12V 33A

SSD: Intel X25-M 80GB MLC SSD SATA II 3 GB/s - FW: 8820
HDD: Western Digital Caviar SE16 500 GB WD5000AAKS 16 MB SATA-II - (4) in (2) RAID-1 (Mirror) Arrays

ENC: MacAlly G-S350SU External HDD Enclosure 3.5" eSATA USB 2.0 Aluminum, Universal 12V Adapter - (2) external WD GP 1TB for Movies
ENC: i-Rocks 9410 External HDD Enclosure 3.5" eSATA USB 2.0 Aluminum, Univeral 12V Adapter - (2) external WD GP 1TB for Backups
HDD: Western Digital Caviar GP Green 1 TB WD10EACS 16 MB SATA-II - (2) external Movies, (2) external for Backups

CON: JMicron JMB363 PATA and SATA Controller, PCIe 1x, 1 PATA, 1 SATA, NCQ, Hotplug, RAID 0,1,0+1,JBOD
CON: JMicron JMB322 SATA II 3 GB/s Controller, PCIe 1x, 2 SATA, NCQ, Hotplug, RAID 0,1,JBOD
NIC: Realtek 8111C PCIe GigE
SOU: Realtek ALC1200 8 channel, HD Audio, Coax/Opt S/PDIF - Analog for Speakers, Motherboard Digital S/PDIF to nVidia GTX 260 S/PDIF for DVI->HDMI

DVD: NEC ND-3550A 16x DVD+-RW SL/DL 48X CDR PATA - FW: 1.07
BLU: LG GGW-H20L Blu-ray 6x BD-RE 16x DVD SL/DL 48x CDR SATA - FW: YL05

MON: HP LP2475w 24-inch LCD H-IPS Monitor Wide Gamut 102% NTSC 6-12ms Response - 1920x1200x32 60Hz, DVI, GIG122/GIG052, Bri 15, Con 80, 9300K
KBD: Microsoft Natural Keyboard Pro USB/PS2 Media Keys
MOU: Microsoft IntelliMouse Explorer 3.0 Optical USB/PS2 Scroll-Wheel 5-Button
JOY: CH Products Fighterstick USB 3 axes 24 buttons
THR: CH Products Pro Throttle USB 3 axes 24 buttons
PED: CH Products Pro Pedals USB 3 axes

ROU: Linksys BEFSR81 EtherFast Cable/DSL Router 8-port Switch 100MBps FW: 2.51.3

OSS: Microsoft Windows 7 Release Candidate Build 7100
[/size]


Rail +5 V on After Prime95 Blend Stress Test - +5.02 V



Rail +5 V on Prime95 Blend Stress Test - +4.78 V



Power usage during Boot-up - 251 W



Power usage during Idle OS - 234 W



Power usage during Prime95 Blend Stress Test - 384 W





Intel Core i7 920 2.66 GHz D0, Asus P6T 0603, G.Skill 6GB DDR3-1600 C8 2T, Xigmatek HDT-1284EE - CPU 3.6 GHz (180 x 20) 1.20 V, DRAM 720 Mhz 2;8 8-8-8-21 2T 1.60 V, QPI 1.2125 V - Prime95 Blend Stopped 76C Peak - PowerStrip



Intel Core i7 920 2.66 GHz D0, Asus P6T 0603, G.Skill 6GB DDR3-1600 C8 2T, Xigmatek HDT-1284EE - CPU 3.6 GHz (180 x 20) 1.20 V, DRAM 720 Mhz 2;8 8-8-8-21 2T 1.60 V, QPI 1.2125 V - Prime95 Blend 5-Min 76C Peak - PowerStrip

It's technically within spec because the atx spec calls for +- 5% from norm but it's real close to being out of spec. Voltages to be in spec can be 4.75v-5.25v

4.72V is out of spec. Barely, but still. 5.21V to 4.83V is in spec, but it's very close to the edge. However, a drop in the +5V rail will probably not affect a stress test very much if at all, and considering the problem started occurring after you added a fan which runs solely off the +12V rail, I doubt the voltage drop on the +5V rail has anything to do with it.

Probably the most detailed listing I've seen in a thread like this.

The flaw I see here is that OCZ sells a lot of mediocre to bad quality PSUs. What you may also be experiencing at the moment outside of the voltage drop is also ripple because you're hanging around 75% of the max. If you load the video card at the same time using something like 3Dmark, you may be over 80% possibly causing that 5v to leave spec further.

With around $2000 worth of equipment (SSDs, OC'd i7, Tv Tuner, GTX 260), you really do not want to potentially damage any of those items. I'd say you look into replacing that with a quality 550W - 600W unit if you intend to stay single card.

shadow_419 said:

It's technically within spec because the atx spec calls for +- 5% from norm but it's real close to being out of spec. Voltages to be in spec can be 4.75v-5.25v

Click to expand...

Zero82z said:

4.72V is out of spec. Barely, but still. 5.21V to 4.83V is in spec, but it's very close to the edge. However, a drop in the +5V rail will probably not affect a stress test very much if at all, and considering the problem started occurring after you added a fan which runs solely off the +12V rail, I doubt the voltage drop on the +5V rail has anything to do with it.

Click to expand...

Being in or out of spec is not so much the issue as seeing the voltage drop 0.3 V on the +5 V rail while it hardly moves at all on the +3.3 V and +12 V rails. It makes me concerned about the power supply. Although according to the sticker this OCZ model supposedly has a very high 40 Amp rating for the +5 V rail that is higher than most power supplies in that high-performance category. Makes me wonder if that 40 A is just another one of those marketing embellishments that see so much with power supplies.

Biskquik said:

Probably the most detailed listing I've seen in a thread like this.

The flaw I see here is that OCZ sells a lot of mediocre to bad quality PSUs. What you may also be experiencing at the moment outside of the voltage drop is also ripple because you're hanging around 75% of the max. If you load the video card at the same time using something like 3Dmark, you may be over 80% possibly causing that 5v to leave spec further.

With around $2000 worth of equipment (SSDs, OC'd i7, Tv Tuner, GTX 260), you really do not want to potentially damage any of those items. I'd say you look into replacing that with a quality 550W - 600W unit if you intend to stay single card.

Click to expand...

Thanks, I tried to give as much possible information up-front as possible because of the issue I'm having overclocking this chip past 3.6 GHz while others are flying by with 3.8-4.0 GHz on air.

I personally like some of the modular units from Corsair or SeaSonic so I might actually be looking towards one of the bit stronger power supplies, 600-750 because from what little I remember about PSU efficiency is that it is best at ~40-50% load and then it degrades quickly with more load or temperatures.

The older OCZ from 4-years ago that I'm using now was a very good power supply at the time with a very high +12 V 33 Amp power load when I used it for my AMD Opteron 175 system with nVidia nForce4 chipset motherboard. It was more than powerful enough that it only used ~250 W during peak load so it was at the 50% mark. I thought that I could just continue using it but when I did the power usage test today and saw it hit 385+ W at Prime95 I thought that this was a little too close to 520 W rating that is often times over advertised.

It's called cross loading. Read one of the reviews on power supplies here at [H]ardOCP and you'll see what happens when one of the rails (+12v in this case) has a high load while the others have light loads. Better designed power supplies deal with cross loads better.

shadow_419 said:

It's called cross loading. Read one of the reviews on power supplies here at [H]ardOCP and you'll see what happens when one of the rails (+12v in this case) has a high load while the others have light loads. Better designed power supplies deal with cross loads better.

Click to expand...

Yes, I knew about cross-loading but I thought it it would affect the +12 V rail also at the same time, but it only drops 0.05 V instead of 0.10 or 0.15 V as I would expect.

It's time for me to take another look at current power supply reviews and pick another one.

Still, I'm curious to find if my 0.30 V drop is a normal occurrence, a warning sign or a sure sign of impending doom.

A drop is normal, but a drop so close to the min spec for tolerance would concern me.

JakFrost said:

Being in or out of spec is not so much the issue as seeing the voltage drop 0.3 V on the +5 V rail while it hardly moves at all on the +3.3 V and +12 V rails.

Click to expand...

Being out of spec is the issue, because computer components are designed to handle input voltages across the entire range of the specification. As long as the voltage is within that range, there shouldn't be a problem.

JakFrost said:

I thought that I could just continue using it but when I did the power usage test today and saw it hit 385+ W at Prime95 I thought that this was a little too close to 520 W rating that is often times over advertised.

Click to expand...

385W from the wall is about 280W DC load considering the 73% efficiency of that PSU at that kind of load (assuming the Kill-A-Watt is reporting accurately which it may not be doing given that your PSU has APFC): http://www.slcentral.com/ocz-powerstream-520adj-power-supply/page6.php

The Powerstream 520W is actually a fairly decent Topower unit, so it should be good enough for your current rig assuming it hasn't degraded too much over the years. With that said, getting a new PSU certainly wouldn't be a bad idea, and if you have the budget for it, I recommend you do so regardless of whether or not your current one is causing any problems. 73% efficiency may have been decent back in 2005, but nowadays, that's pretty much unacceptable, especially since you can get 500W 80Plus PSUs quite inexpensively.

shadow_419 said:

A drop is normal, but a drop so close to the min spec for tolerance would concern me.

Click to expand...

When I started slightly adjusting the +5 V rail while the system was running Prime95 to up the voltage just a tad the readings started bouncing around like crazy hitting as low as +4.35 V and staying there for a period of time even when I was raising the voltage on the rail very slightly. This type of behavior alarmed me since it seemed that the power regulation on this supply is not stable on the +5 V rail.

This is exactly the same conclusion that was found in the review article that Zero82z pointed to.

SLCentral - OCZ PowerStream 520ADJ Power Supply

"The problem reared it's ugly head during test two when the 5V load was greater than the load on the 12V. At this moment, I noticed all of the voltages bouncing back and forth by as much as .2V or MORE! Although the voltages spent most (not all) of their time at one number, this is something that would typically tear up your computer hardware."

After I read this this seemed exactly what was happening in my system and now I'm researching a new power supply to buy since this old one will be retried along with my old AMD Opteron system that it was meant for.

Zero82z said:

73% efficiency may have been decent back in 2005, but nowadays, that's pretty much unacceptable, especially since you can get 500W 80Plus PSUs quite inexpensively.

Click to expand...

Great Article Link

Thank you for linking that that article, it seems that they found the same problem with my power supply that I just found on this new rig. I was surprised that this power supply was listed as one of the recommended ones on a few reviews and also I believe on this HardForum Power Supplies section sticky from that time.

OCZ Choice From 4-Years Ago

I primarily chose it due to this recommendation and also because it had a standard 80mm fan in the back and I chose it because I have a split-compartment case the Lian-Li PC-V1200 Plus and I thought that it would be a good idea if the intake fan was in the back of the power supply pushing the air since there really isn't much space to push the air out from under the power supply. There is only about 1-inch of space with a special stand-off from the bottom of the power supply to the bottom of the case but luckily there are vent holes drilled there to push the air out of the bottom of the case and since my case is on wheels there is about 1.5-inches of space below the case.

This isn't exactly the best ventilation setup for a power supply but since most of the good power supplies these days come with 120mm down-blowing fans I have no choice but to use that.

The only alternative that existed previously with a back fan was the PC Power & Cooling supplies but it seems that since OCZ Technology took them over there are quite a lot of dead-on-arrival complaints from users buying these power supplies on Newegg. On top of that those power supplies were known to be loud. That doesn't exactly make me feel like I have a choice at this point but to go with a 120mm fan supply.

Unless someone can recommend a great alternative with a back blowing fan.

In any case it is time to retire it along with my old AMD Opteron system and upgrade to a 80+ efficiency power supply with more stable +5 V rail.

Power Load

I'm doing research into power supplies and I have to decide which one to buy. Judging from my power usage numbers and taking them at face value knowing that Active Power Factor Correction circuitry is not hiding some huge transient loads that the Kill-a-Watt P3 isn't seeing I have to say that my Idle load is ~230 W and maximum CPU load is ~390 W. If I was to throw in a maximum GPU load then the number would climb into +400 W. I might risk doing just that for a minute or two to see how much juice this rig could pull but I'm concerned about burning out this power supply knowing how it has problems already at ~390 W peak CPU load.

Still the question remains, how much power should I buy considering that I'm not an SLI fanboy since I always think that the next gen card usually does better than 2x SLI last gen cards so I switch to that instead. There are (4) 7,200 RPM drives in this case along with a TV capture card and a DVD and Blu-ray burner but of course not everything is going to be used to the maximum at the same time.

I have to figure out where my normal gaming load would be between idle and peak with a bit of CPU and GPU usage at the same time so I'm going to do a little load test.

I also used the liked-and-hated eXtreme Power Supply Calculator Lite v2.5 to plug in some numbers from my current system and to add some memory and another SSD into the mix, put in correct overclocking numbers, 100% peak load, and 20% capacitor aging and it threw back 617 W recommendation at me. That seems to be almost perfect for the power supply that I have in mind below.

But is a new 620 W power supply the right size for my loads or should I go higher?

Power Supply Choices

I am a fan of Corsair and Seasonic since these two companies usually end up with very good overall power supply results and use good quality design and products. They might not win the best awards but they are consistent with good products so I'm going to do some research now on their power supplies.

I am considering the power supply below right now and I'll be focusing my review research on this model to see if it turns up any skeletons in the closet.

CORSAIR CMPSU-620HX 620W ATX12V v2.2 and EPS12V 2.91 SLI Certified CrossFire Ready 80 PLUS Certified Modular Active PFC Compatible with Core i7 Power Supply - Retail
Cost: $139.99 (-$20.00 rebate) = $119.99

JakFrost said:

This is exactly the same conclusion that was found in the review article that Zero82z pointed to.

SLCentral - OCZ PowerStream 520ADJ Power Supply

"The problem reared it's ugly head during test two when the 5V load was greater than the load on the 12V. At this moment, I noticed all of the voltages bouncing back and forth by as much as .2V or MORE! Although the voltages spent most (not all) of their time at one number, this is something that would typically tear up your computer hardware."

Click to expand...

Actually, that isn't really true. Jon saw those results when using a load on the +5V rail that was higher than the load on the +12V rail. This is not a normal crossloading pattern for a modern system, and you are most certainly putting much more of a load on the +12V rail than you are on the +5V rail. However, what you're experiencing is certainly not ideal behaviour.

JakFrost said:

I'm doing research into power supplies and I have to decide which one to buy. Judging from my power usage numbers and taking them at face value knowing that Active Power Factor Correction circuitry is not hiding some huge transient loads that the Kill-a-Watt P3 isn't seeing I have to say that my Idle load is ~230 W and maximum CPU load is ~390 W. If I was to throw in a maximum GPU load then the number would climb into +400 W. I might risk doing just that for a minute or two to see how much juice this rig could pull but I'm concerned about burning out this power supply knowing how it has problems already at ~390 W peak CPU load.

Still the question remains, how much power should I buy considering that I'm not an SLI fanboy since I always think that the next gen card usually does better than 2x SLI last gen cards so I switch to that instead. There are (4) 7,200 RPM drives in this case along with a TV capture card and a DVD and Blu-ray burner but of course not everything is going to be used to the maximum at the same time.

I have to figure out where my normal gaming load would be between idle and peak with a bit of CPU and GPU usage at the same time so I'm going to do a little load test.

Is a new 620 W power supply the right size for my loads?

Power Supply Choices

I am a fan of Corsair and Seasonic since these two companies usually end up with very good overall power supply results and use good quality design and products. They might not win the best awards but they are consistent with good products so I'm going to do some research now on their power supplies.

Click to expand...

If you won't be going with a multi-GPU system in the future, then I would recommend 500W or more. The Corsair HX620 or TX650 would be good choices, as would the Antec Truepower New 550W and 650W models (made by Seasonic) and Antec Earthwatts 500W or 650W (made by Delta Electronics and excellent PSUs as well). If you want a little more power, I would suggest the Corsair HX750, Seasonic M12D 750W, or Antec Truepower New 750W.

Zero82z said:

If you won't be going with a multi-GPU system in the future, then I would recommend 500W or more. The Corsair HX620 or TX650 would be good choices... If you want a little more power, I would suggest the Corsair HX750, Seasonic M12D 750W, or Antec Truepower New 750W.

Click to expand...

The recommendations that you listed without Antec in the picture look almost like the Newegg Power Search results that I got myself when I did a search for modular power supply 600-800 W from Seasonic or Corsair.

I'm favoring the Corsair 620HX modular model because in all the time that I've been gaming I never could get myself to buy into SLI since the benefits were too low for the price to pay.

My system is capable of SLI with my GTX 260 card if I threw a 750 W power supply at it but I could never justify the need before. However, now I have a 24" good quality H-IPS screen running at 1920 x 1200 so that SLI might be good if I want full resolution gaming but the cost of another card is another $200 that I don't really have right now. I guess that if I do choose to jump onto the SLI bandwagon sometime in the future I'll just have to sell-off the 620 W power supply and upgrade to the 750 W model at that time.

Corsair 620HX is my choice. I'll buy it now as not to wait. I've done a bit of reading of good reviews about it and it's all positive.

PS: For my friend's Ultimate HTPC build I used the Corsair 520HX and that was a good power supply choice so that is also the reason why I'm choosing the 620HX for myself.

The HX620 will do great.

Zero82z said:

The HX620 will do great.

Click to expand...

I placed the order yesterday but I'm a little curious if I should have paid the extra $25-30 and purchased a 750 W power supply like one of the two below just in case I ever get another video card and decide to go SLI.

I have to read up on some of the video card reviews again and this time pay more attention to the SLI results that I have been ignoring previously since I've been discounting SLI when I used to use a 19" CRT at 1280x1024 but now with this 24" LCD at 1920x1200 SLI might offer actual benefits.

The only thing is that while not playing any games the system would draw ~250 W of power during normal usage from a 750 W power supply, only using a third of the capacity. This might throw energy efficiency out of the window on the power supply since it isn't being used very much. Have to read up on the efficiency curves also.

Using that power calculator thing when I throw in 2 cards for SLI it throws back 681 W meaning a 750 W is not exactly out of the question.

I'm debating whether I should cancel my order and just spend the extra $25 for the 750 W power supply.

CORSAIR CMPSU-750HX 750W ATX12V 2.3 / EPS12V 2.91 SLI Ready CrossFire Ready 80 PLUS SILVER Certified Modular Active PFC Power ... - Retail
Cost: $164.99




SeaSonic M12D SS-750 750W ATX12V V2.3/EPS12V V2.92 SLI Ready CrossFire Ready 80 PLUS SILVER Certified Modular Active PFC ... - Retail
Cost: $179.99 - $30.00 rebate = $149.99

JakFrost said:

The only thing is that while not playing any games the system would draw ~250 W of power during normal usage from a 750 W power supply, only using a third of the capacity. This might throw energy efficiency out of the window on the power supply since it isn't being used very much. Have to read up on the efficiency curves also.

Click to expand...

Two things: each 80Plus level has a minimum efficiency requirement for 20% load, which is 80% for 80Plus standard, 82% for Bronze, 85% for Silver, and 87% for Gold. The second thing is that at such a low load, a few percent difference in efficiency has an almost negligible effect on actual power usage since 5% of 200W for example is only 10W which is a drop in the bucket. So it's really nothing to worry about. By the way, The HX750/850 and Seasonic M12D 750W/850W are all certified 80Plus Silver and have an efficiency of 85% or higher at 20% load.

JakFrost said:

I placed the order yesterday but I'm a little curious if I should have paid the extra $25-30 and purchased a 750 W power supply like one of the two below just in case I ever get another video card and decide to go SLI.

Click to expand...

The HX620 is enough for SLI with most cards, but a 750W or higher PSU would be preferable.

Zero82z said:

By the way, The HX750/850 and Seasonic M12D 750W/850W are all certified 80Plus Silver and have an efficiency of 85% or higher at 20% load.

The HX620 is enough for SLI with most cards, but a 750W or higher PSU would be preferable.

Click to expand...

Newegg just shipped my Corsair 620HX so it's too late to cancel but I have the option of refusal on delivery, and I'll get all my money back. I did this once already and it worked fine, I already apologized in advance to them for doing it last time and possibly having to do it again with this order and I offered to pay for the shipping but they said not to worry.

I'm doing research on the Seasonic M12D and Corsair 750HX power supplies to determine if I want to spend a little more to get those.

Is 750 W Necessary?

I don't really know if I'll need 750 W for a simple SLI for GTX 260 because that 620HX might be able to handle it considering the fact that I won't be maxing out the CPU and both GPU's to full even while playing the most demanding games. Of course having the extra headroom would be a good idea but I'm having a hard time deciding. The thermals in the bottom of the case are not so great either so having the extra head room in the power supply might be a good idea also. I'm leaning towards the 750 W now and I have to decide which one to get, Corsair 750HX or Seasonic M12D 750W.

I'm reading this article now about the efficiency of the power supply and noise and it seems that the power supply is most efficient at low loads which is great since most of the time it would be running around the ~250 W range being the most efficient.

AnandTech - Seasonic M12D 850W: DC-to-DC Perfection?

JakFrost said:

Is 750 W Necessary?

Click to expand...

Will an HX620 blow up if you run your PC on it with two cards in SLI? No. Will an HX750 run cooler and last longer compared to an HX620 under those load condition? Yes. 750W isn't necessary, but it is preferable.

JakFrost said:

http://images.anandtech.com/reviews/psu/2008/seasonic-m12d/eff-comp.png

http://images.anandtech.com/reviews/psu/2008/seasonic-m12d/acoustics.png

Click to expand...

Don't hotlink images.

Zero82z said:

Will an HX620 blow up if you run your PC on it with two cards in SLI? No. Will an HX750 run cooler and last longer compared to an HX620 under those load condition? Yes. 750W isn't necessary, but it is preferable.

Don't hotlink images.

Click to expand...

Yes, I agree with you about the 620HX being enough but the 750HX giving more head room. Since I'm having this nagging doubt in my mind since last night I'm going to take the hit and spend the extra $25 on the 750 W to give myself extra head room.

There might be another GTX 260 down the line for me and it's better to be prepared ahead of time with a more powerful power supply now. Spending the extra $25 is worth not having to go through the hassle of selling the power supply and installing a new one with cabling.

PS: I removed the hotlinked images since you mentioned it. I really wish that HardForum would reconsider the rules since linking to useful graphs like the ones from review articles is probably not doing very much to eat up bandwidth from hosts like review sites. Plus, these hotlinks with URL links around them provide a kind of word-of-mouth advertisements to the review sites. I always reference and attribute the source of info and link to the source of the images in my posts. I do that a lot for products from Newegg and sometimes from AnandTech and no issues so far. Even with mods commenting in my threads.

JakFrost said:

I removed the hotlinked images since you mentioned it.

Click to expand...

You should remove the ones in your other posts as well.

JakFrost said:

PS: I removed the hotlinked images since you mentioned it. I really wish that HardForum would reconsider the rules since linking to useful graphs like the ones from review articles is probably not doing very much to eat up bandwidth from hosts like review sites. Plus, these hotlinks with URL links around them provide a kind of word-of-mouth advertisements to the review sites. I always reference and attribute the source of info and link to the source of the images in my posts. I do that a lot for products from Newegg and sometimes from AnandTech and no issues so far. Even with mods commenting in my threads.

Click to expand...

The Issue is that you're using the bandwidth of those sites without permission. If you want to use the images host them on a site like imageshack and then link there.

Well, I got the new Corsair 750HX power supply today and I am very happy with it. I tested it and it is okay, installed it, and ran a Prime95 stress test on it for a few hours to make sure that it works okay. Everything is fine and there were no problems with any voltage drops during the stress test on any of the rails.

I love the packaging with the velvet bag for the power supply and the cables. The thin black ribbon cables make cable management a breeze and I don't need to go crazy tying the cables together as before because the case is neat right away.

I also replaced my SATA cables with new blue ones with a metal latch to get a secure lock on the cables but found that the Intel SSD doesn't use the click lock and the crappy JMicron internal ports are of the SATA I variety and don't even allow cables with click-locks to connect.

I'll post pictures and details of this power supply tomorrow. I'm planning a full CPU and GPU load test along with hard drives and optical drives to see if I can get maximum power draw out of it. Should be fun.

PS: Bad news, one of my Western Digital Caviar 500 GB drives died today. This happened after I connected it to the new power supply but I have been getting failure events on some of hard drives for a few weeks now. I think that the old power supply just was killing my drives and it finally finished this one off. The SMART Status today changed on it to BAD so I used WD's web site to do a quick Advanced RMA on the drive and I should have a replacement in a few days. Good thing that WD gives such long warranty even on OEM drives, because the production date on the drive is 2006-08-15.

Good to hear that everything is working out (more or less). It's a shame about the HD, but at least you should be getting a replacement pretty quickly.

New Power Supply

Here are the pictures of the load testing on the new Corsair HX750W power supply.

This power supply already seems more efficient since on CPU Load my old OCZ PowerStream 520W pulled 384 W but this new one only does 326 W, for a difference of 58 W. On Idle the old one did 234 W and new one 200 W for a difference of 34 W. Overall it seems more efficient.

I did not run a CPU & GPU Load test on the old power supply but on this one I did a Prime95 8-threads and also did 3DMark Vantage GPU Test 2 - New Calico and hit a peak of 424 W.

One thing about this power supply is that the +5 V rail and the others are absolutely stable, unlike my other power supply that had a 0.30 V drop in the +5 V rail under load and probably further fluctuations that I didn't notice. This was the most important reason for this power supply.

I included the output from my APC Back-UPS XS 1500 VA showing the various power usage of the computer, monitor, router, cable modem, and desk lamp during the different stress test scenarios. Basically the numbers are Idle 302 W, CPU Load 423 W, and CPU + GPU Load 510 W.


750 W Is Too Much Honestly

I think that the 750 W power supply is too much honestly. The peak CPU + GPU test showed only 423 W and CPU Load 326 W for a 98 W difference. Now if we include a second video card into this picture it would likely pull less than 98 W because in SLI mode the second card is never fully used so it doesn't draw so much more power. At the maximum my system with nVidia GTX 260 in SLI would draw 521 W which would be handled just fine by the Corsair HX620W model. In reality when doing just the GPU load tests that I didn't post the power draw is around the ~330 W for most of 3DMark Vantage and with SLI it would be less than 428 W so a 620 W power supply would be more than enough.

At this point I paid the extra $25 ($45 with rebate) for the 750W power supply and frankly it is not worth it! However, I already opened and installed this power supply and a bit of it got a little scratched on the side so I'm stuck with it. The other power supply is already going to be delivered tomorrow so I can Refuse Delivery on it so it goes back and I get a refund.

If I just ran the full CPU + GPU Load test on the old power supply and saw the ~482 W result I would have probably went with the 620 W model and it would have been enough.

I'm sure that having the extra 130 W head room with this 750 W model over the 620 W model is not a bad thing to have but if you consider that it cost me $45 more for a ephemeral benefit then it was not worth it. Especially when normal maximum usage will usually be either CPU load with 326 W maximum draw or GPU with slight CPU load which ends up almost the same at ~330 W. With SLI that would be the same for CPU load and GPU load with a maximum of ~428 W. So a 620 W power supply should handle this type of a load just fine with 200 W head room. Now I'm stuck with a 750 W power supply that is only loaded at 200 W (26%) when the computer is idle, 326 W (46%) when CPU loaded or doing gaming, with a possibility of SLI for ~428 W (57%) load. That is a huge waste of potential for this power supply since it will never go above 60% usage.

I'm sure that some of you will point out that the efficiency of this power supply is the best at roughly 50% load so that it would be the most efficient when it is loaded but frankly the little ~3% change in efficiency is so small that any energy savings attributed to it are probably fractional compared to the extra $25 ($45 with rebate) costs of it. It would probably take months of non-stop usage at 50% load to get the money back and nobody does that.

I should have listened to some of the smarter reviewers like Christoph Katzer from AnandTech who say that the latest craze with huge power supplies is just an unnecessary marketing fad and a race for watts to nowhere that nobody really needs. Word of warning to you folks, don't overbuy a power supply that you don't need.

The only saving grace for the Corsiar HX750W power supply is that it includes 4-PEG (6/8-pin) connectors for the PCI-e graphics cards and new cards that require the 8-pin PEG connector where as the Corsair HX620W only includes 2-PEG (6-pin) connectors. That is about the only reason that I am not quite angry about this power supply since I know that if I go with SLI in the future or when I replace my GTX 260 with something else this power supply will be ready.



Results From Corsair HX750W

Kill-a-Watt Power Meter
Intel Core i7 920 2.66 GHz D0
Asus P6T 0603
G.Skill 6GB DDR3-1600 C8 2T
Xigmatek HDT-1284EE
Corsair 750HX

Idle - 200 W



CPU Load - 326 W



CPU + GPU Load - 424 W







Power Usage - Idle - Kill-a-Watt 196 W, APC UPS 302 W





Power Usage - CPU Load - Kill-a-Watt 326 W, APC UPS 423 W





Power Usage - CPU + GPU Load - Kill-a-Watt 424 W, APC UPS 510 W





Lian-Li PC-V1200 Plus Case - Corsair 750HX - Drive Bay



Lian-Li PC-V1200 Plus Case - Intel Core i7 920 2.66 GHz D0, Asus P6T 0603, G.Skill 6GB DDR3-1600 C8 2T, Xigmatek HDT-1284EE, Corsair 750HX - Case Inside

JakFrost said:

750 W Is Too Much Honestly

I think that the 750 W power supply is too much honestly. The peak CPU + GPU test showed only 423 W and CPU Load 326 W for a 98 W difference. Now if we include a second video card into this picture it would likely pull less than 98 W because in SLI mode the second card is never fully used so it doesn't draw so much more power. At the maximum my system with nVidia GTX 260 in SLI would draw 521 W which would be handled just fine by the Corsair HX620W model. In reality when doing just the GPU load tests that I didn't post the power draw is around the ~330 W for most of 3DMark Vantage and with SLI it would be less than 428 W so a 620 W power supply would be more than enough.

At this point I paid the extra $25 ($45 with rebate) for the 750W power supply and frankly it is not worth it! However, I already opened and installed this power supply and a bit of it got a little scratched on the side so I'm stuck with it. The other power supply is already going to be delivered tomorrow so I can Refuse Delivery on it so it goes back and I get a refund.

Click to expand...

If you recall, I suggested the HX750 only if you intend to add a second GPU in the future. For a single GPU, I said the HX620 would be more than fine.

Also, I'm sure that if you really wanted to return the HX750, the little scratch on the side wouldn't be such a big deal.

Zero82z said:

If you recall, I suggested the HX750 only if you intend to add a second GPU in the future. For a single GPU, I said the HX620 would be more than fine.

Also, I'm sure that if you really wanted to return the HX750, the little scratch on the side wouldn't be such a big deal.

Click to expand...

You gave me very good feedback and advice. I had the doubts about the Corsair HX620W jumping around in my head because of "what if I want SLI..." so I jumped on the 750 W. You gave a good recommendation and feedback so I really appreciate that.

I'm just a little pissed that I'll only be using ~50% of this power supply max but that has advantages in terms of efficiency, acoustics, and thermals so it's not like this was a bad choice at all. The only reason why I'm not really freaking out about the price are the extra connectors on this power supply.

I won't be returning the Corsair HX750W since I think that the 4-PEG 8-pin connectors might be one of those things that I might need in the future even if I don't go for SLI since it's very possible that the next generation of cards will require 8-pins instead of just 6-pins. Having 4 connectors opens up the possibility of SLI also. Since I'm running 1920 x 1200 that means that SLI isn't so far fetched either if I want to do full resolution with 4x AA/AF and keep 60 FPS rates on newer games.

If I have to consider the fact that the $25 (or $45 after rebate) is the money that I pre-spent to avoid the future hassle of time and effort spent for uninstalling a power supply, selling it on eBay, buying a new one, and then installing it. The extra money spent is a small price to pay for the additional effort of upgrading a power supply in the future. (Hopefully, nVidia or ATI won't go super power-saving crazy and start backing down on GPU power requirements, then all of this forethought will be for naught.)

Oh, and the most important thing is that my +5 V rail is now completely stable and hopefully this will prevent my other hard drives from getting killed by my power supply like I believe the last one did. I am happy that I did this power supply upgrade since it also cleaned up the inside of my case. As you can see there is no more power cable clutter and the thin black ribbon cables keep things very neat even before I tied them up for cable management.