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BoeingGuy

ATI Radeon 4870 X2--Power Supply?

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Hi all,I'm researching buying a 4870 X2 since all MS games will run better that way. Will I need a better PSU/Power Supply, seeing as the 4870 X2 consumes 245 more watts than the 8800 GT?Thanks!

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Hi,A review here: http://www.hardocp.com/article.html?art=MT...GhlbnRodXNpYXN0And another here:http://www.anandtech.com/video/showdoc.aspx?i=3354&p=8You could estimate the power needed by these reviews. I'm not familiar with your PSU, but if it's able to keep up 600W it should be OK.Ulf BCore2Duo X6800 3.3GHz4GB RAM Corsair XMS2-8500C5BFG 8800GTX, Creative SB X-FiFSX Acc/SP2, Vista 32

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>Hi all,>I'm researching buying a 4870 X2 since all MS games will run>better that way. Interesting, how did you come to that conclusion?

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Hi Boeinguy,I'm wondering now about just how much overkill we are doing now with powersupplies. I used two different suggested PS configurators to determine what I needed for my current rig:QX9650@4.2Gh/1.4125v vCore2 15K.3 SCSI drives2 SATA 3Gb/s drives4GB DDR38800GT/OC to 7004 fans2 optical drivesNow, add this:Alesis powered 8 Channel mixerRoland A90Ex stage pianoKorg Wavestation A/D sound module4 port powered USB hubNow here's the clincher: recently I bought a 1,500W APC UPS which displays load in watts. When I am running FSX full tilt, fully overclocked, THE SUCKER SHOWS 320W, that's it! That's absolute peak. It's usually bouncing around between 290 and 305W.So, why the heck did I buy a 750W PS? I think the recommendations on wattage rating for PC powersupplies represents serious overkill, unless I am missing something in this. Perhaps the LCD on this new APC UPS is bogus, I don't know. Can't see any reason why I can't run 4870 x2 so just may. The FPS drop is troublesome though compared to my 8800GT. I'd love the headroom for first person shooters, but be a drag to take a hit in FSX.NoelQX9650 w/ Retail HSF|ASUS P5E3 Premium WiFi|4GB Muskin Ascent 7-6-6-18 1T DDR3-1600|EVGA 8800GT|Seagate SATA 2 x 2|Seagate Cheetah 15K.x|XP Pro SP2|Vista 64--maybe never to be installed

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>So, why the heck did I buy a 750W PS?Maybe because your PSU isn't able of delivering 750W continuously? What model do you use?You would increase the load about 200W when going from a 8800GT to the 4870 X2. http://www.anandtech.com/video/showdoc.aspx?i=3354&p=8I would never purchase a PSU that's barely able to deliver the watts and amps needed. I would go for a lot of headroom and having the PSU to performe well without any risk for overheating. If you did buy a 500W PSU, you would have to replace it if you would go for a 4870 X2. IMO a 750W PSU isn't overkill.Ulf BCore2Duo X6800 3.3GHz4GB RAM Corsair XMS2-8500C5BFG 8800GTX, Creative SB X-FiFSX Acc/SP2, Vista 32

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I agree. I fail to see how any single card graphics solution system needs any more than 500W quality power supplied, yet people around here talk of 1000W+ supplies to handle "the load" on such systems. I manage to survive on "only" a 480W PSU with my system.Gary

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>I agree. I fail to see how any single card graphics solution>system needs any more than 500W quality power supplied, yet>people around here talk of 1000W+ supplies to handle "the>load" on such systems. I manage to survive on "only" a 480W>PSU with my system.>>GaryMy guess is that you wouldn't survive with the 4870 X2.Ulf BCore2Duo X6800 3.3GHz4GB RAM Corsair XMS2-8500C5BFG 8800GTX, Creative SB X-FiFSX Acc/SP2, Vista 32

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Thanks for the replies guys, for now I'm sticking with the 8800 GT.Djt, I came to that not-so-fixed conclusion because ATi drivers don't seem to have a problem with MS games. NVIDIA seems to be constantly plagued by driver errors when it comes to MS games.Well that's what happened to me. An unstable overclock that I failed to notice/test caused my card to keep crashing. Lowering the Core/Shader/Mem clocks by 20 MHz stabilized everything again.Cheers,

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>>So, why the heck did I buy a 750W PS?>>Maybe because your PSU isn't able of delivering 750W>continuously? What model do you use?>>You would increase the load about 200W when going from a>8800GT to the 4870 X2.>http://www.anandtech.com/video/showdoc.aspx?i=3354&p=8>>I would never purchase a PSU that's barely able to deliver the>watts and amps needed. I would go for a lot of headroom and>having the PSU to performe well without any risk for>overheating. If you did buy a 500W PSU, you would have to>replace it if you would go for a 4870 X2. IMO a 750W PSU isn't>overkill.Ulf, I bought the thing because the configurator, and many comments in here, suggested this is what is needed. I question this now. I have allegedly one of the best PS available, a PC Power n Cooling 750W with big 12v rail. With my very overclocked PC, and MULTIPLE other pieces of hardware connected, I don't even get to 50% of the rated capacity. I maintain it's overkill that has come from people using configurators and from all the other "knowledge" in forums such as this, where people have good intentions but may really not know what they are talking about from an electrical engineering standpoint. Even so, it's chump change to buy a 750W PS :()

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Noel,I get your point. I'm no expert so I trust you being right on this one. But I still have a feeling that you should have headroom between your actual peak load and the PSU peak capacity. Is this a mistake by me?Ulf BCore2Duo X6800 3.3GHz4GB RAM Corsair XMS2-8500C5BFG 8800GTX, Creative SB X-FiFSX Acc/SP2, Vista 32

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One of the most important things today with power supplies is the ability of the 12v rail(s) to meet the demand of the GPU or other hardware. I know - I have a Sapphire ATI X1950XT which draws 30 amp at 12v, my PSU gave 18A on each of two 12v rails so I kept having crashes. I now have a PSU which gives 54 amps on a single 12v rail and things work fine. Except I am a bit concerned now that the previous under-supply might have damaged my GPU, which apparently can happen.So the new moral is that the total wattage is not necessarily the best paramater to look at. Lots of good info on this topic at the Sapphire forum. http://www.sapphiretech.com/en/forums/forumdisplay.php?f=4NigelVancouver

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>Noel,>>I get your point. I'm no expert so I trust you being right on>this one. But I still have a feeling that you should have>headroom between your actual peak load and the PSU peak>capacity. Is this a mistake by me?>>Ulf BSure, headroom sounds wise. But 120% headroom? Remember, with the numbers I gave, this is a penryn and 8800 overclocked significantly, so the headroom was their bigtime. Anyway, I only bring it up for this who believe they need to go buy a 1,000W PS if they add an X2 video card, or even in crossfire. It appears I can install TWO X2 cards and still have breathing room.QX9650 w/ Retail HSF|ASUS P5E3 Premium WiFi|4GB Muskin Ascent 7-6-6-18 1T DDR3-1600|EVGA 8800GT|Seagate SATA 2 x 2|Seagate Cheetah 15K.x|XP Pro SP2|Vista 64--maybe never to be installed

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>One of the most important things today with power supplies is>the ability of the 12v rail(s) to meet the demand of the GPU>or other hardware. >>I know - I have a Sapphire ATI X1950XT which draws 30 amp at>12v, my PSU gave 18A on each of two 12v rails so I kept having>crashes. I now have a PSU which gives 54 amps on a single>12v rail and things work fine. Except I am a bit concerned>now that the previous under-supply might have damaged my GPU,>which apparently can happen.>>So the new moral is that the total wattage is not necessarily>the best paramater to look at. This is my understanding as well, so this is why I bought one with a 60A 12v rail, or thereabouts.

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>Djt, I came to that not-so-fixed conclusion because ATi>drivers don't seem to have a problem with MS games. NVIDIA>seems to be constantly plagued by driver errors when it comes>to MS games.I

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>>Sure, headroom sounds wise. But 120% headroom? Remember,>with the numbers I gave, this is a penryn and 8800 overclocked>significantly, so the headroom was their bigtime. Anyway, I>only bring it up for this who believe they need to go buy a>1,000W PS if they add an X2 video card, or even in crossfire. >It appears I can install TWO X2 cards and still have breathing>room.>Well, my discussion was about adding a 4870 X2 to a pc, which was the OP's question. You would probably end up with your system peaking between 520W and 560W.I quote my first response to your original post:>Maybe because your PSU isn't able of delivering 750W continuously? >What model do you use?>You would increase the load about 200W when going from a 8800GT to >the 4870 X2. http://www.anandtech.com/video/showdoc.aspx?i=3354&p=8>I would never purchase a PSU that's barely able to deliver the watts >and amps needed. I would go for a lot of headroom and having the PSU >to performe well without any risk for overheating. If you did buy a >500W PSU, you would have to replace it if you would go for a 4870 >X2. IMO a 750W PSU isn't overkill.I totally agree that using a 750W with your present config with a 8800GT is overkill.Ulf BCore2Duo X6800 3.3GHz4GB RAM Corsair XMS2-8500C5BFG 8800GTX, Creative SB X-FiFSX Acc/SP2, Vista 32

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It's been awhile since I looked at calculating electrical power with Ohm's Law. I believe, and could be wrong, but the problem is compairing 120v AC power supplied by UPS to the 5/12v DC supplied by the computer PS.The UPS power load display is what the computer PS is using to operate. That would be different from what the computer is demanding from the PS.If you want to determine how much load is on the PS, you would need a load meter on the PS not the UPS.Maybe someone current in Ohm's Law can better explain. From what I recall, power (watts) at 12 volts at a given amperage would be different than 120 volts at the same amperage.P=IxE or Power/Wattage (P) equals current/amperage (I) times voltage (E).120 volts times 20 amps = 2400 watts12 volts times 20 ampes = 240 wattsHope I didn't mess this up.Regards,Richard

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>It's been awhile since I looked at calculating electrical>power with Ohm's Law. >>I believe, and could be wrong, but the problem is compairing>120v AC power supplied by UPS to the 5/12v DC supplied by the>computer PS.This sounds believeable Richard. Thanks for the insight. I DOES however, suggest a 1,500W UPS was . . . overkill :()

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>It's been awhile since I looked at calculating electrical>power with Ohm's Law. >>I believe, and could be wrong, but the problem is compairing>120v AC power supplied by UPS to the 5/12v DC supplied by the>computer PS.>>The UPS power load display is what the computer PS is using to>operate. That would be different from what the computer is>demanding from the PS.>>If you want to determine how much load is on the PS, you would>need a load meter on the PS not the UPS.>>Maybe someone current in Ohm's Law can better explain. >>From what I recall, power (watts) at 12 volts at a given>amperage would be different than 120 volts at the same>amperage.>>P=IxE or Power/Wattage (P) equals current/amperage (I) times>voltage (E).>>120 volts times 20 amps = 2400 watts>>12 volts times 20 ampes = 240 watts>>Hope I didn't mess this up.>>Regards,>>RichardWatts are the true power ratings. So when you put a watt meter on the 12v hardware, it's measuring watts. On the 12v side, the amperage is increased to compensate for the low voltage, and it's reporting in watts. The UPS' watt meter is measuring how much power the PC draws, thru it's powersupply. I can imagine, due to various resistances involved between the components, there would be a slightly inexact representation as one over the other. I'm also seeing how the demand source (the pc CPU/GPU and other power users) has to *suck* hard, to pull in the requisite power. Therefore, the demand side will be HIGHER (in watt demand), while the source power can simply push along what is needed, which will display as less wattage. I wonder what the conversion factor would be? Have to tinker with that idea . . .NoelOr, inherent inefficiencies in the conductors involved will widen this disparity.QX9650 w/ Retail HSF|ASUS P5E3 Premium WiFi|4GB Muskin Ascent 7-6-6-18 1T DDR3-1600|EVGA 8800GT|Seagate SATA 2 x 2|Seagate Cheetah 15K.x|XP Pro SP2|Vista 64--maybe never to be installed

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Thats because you are looking at the inverted load being supplied to the AC side of the PSU and NOT the DC demand the PSU is delivering to the internal systemHUGE difference... If I had time I would post the formulas for that, look them up on the net... check into VA and conversionsAnyone running less than 600watts on a quad core and overclocking is pushing their luck even with a mid-grade video card and that also depends on the PSU maker. A PC Power and Cooling PSU delivers where most would be lucky to deliver 65-75% of the advertised ability. I dont know how many times I have solved performance problems where no crash was seen, only poor performance by replacing the PSU with the right unit. Usually the system temps dropped significantly at the same time.EDIT: I see Richard already stepped in and somewhat corrected this complete misconception of watt draw. AC input and DC output are 2 different animals. Then there are the rails and how they are designed which also factors in. One would be glad they have that 750watt PCP&C unit after calcualting everything correctly because then HEAT and overhead current also play into a system for stability and performance.Goes hand in hand with many other misconceptions I still see posted around hereThe minimum UPS I would personally spec for a clocked quad core system and a 24inch LCD monitor with several hard drives and a decent video card would provide 658 W @ 1096 VA

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There are raw formulas to estimate VA and convert it to power however there is much more to testing for efficiency between input and output draw than simply guessing and using basic formulas or even using meters at home. A bench test unit designed specifically for that purpose is required and PCP&C uses such a system when rating their PSU's and checking them for QCThe EFF rating is based on the full load ability of the PSU, therefore the ability is variable based on the load and HEATη (EFF) = Σ Po,ii------- X 100P inThat 750watt PSU is worth its weight in gold for a cool and stable system, and it overts future upgrade costsI do agree with a dual core processor and a typical mid range video card on 2GB of memory, 750watts is very overkill. I would still not run any system today with 3D hardware/use on less than a 500-600 TRUE watt PSU. Most el'cheap-o crap sold to be 500-600watts only delivers 65-75% of that

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>There are raw formulas to estimate VA and convert it to power>however there is much more to testing for efficiency between>input and output draw than simply guessing and using basic>formulas or even using meters at home. A bench test unit>designed specifically for that purpose is required and PCP&C>uses such a system when rating their PSU's and checking them>for QC>>The EFF rating is based on the full load ability of the PSU,>therefore the ability is variable based on the load and HEAT>>η (EFF) = >>Σ Po,i>i>------- X 100>P in>>>>That 750watt PSU is worth its weight in gold for a cool and>stable system, and it overts future upgrade costs>>I do agree with a dual core processor and a typical mid range>video card on 2GB of memory, 750watts is very overkill. I>would still not run any system today with 3D hardware/use on>less than a 500-600 TRUE watt PSU. Most el'cheap-o crap sold>to be 500-600watts only delivers 65-75% of that Nick I am going to install a 4870 or 4870x2 I'm pretty sure. I'm thinking I'm still ok with that, and I base it on this utility as an estimator: http://www.extreme.outervision.com/PSUEngineThey have all my parts represented except the 4870x2. I used the 3870x2, and it comes out to 620W PS rating. I'm guessing I'll be ok still with the 750W from PC P&C. You think?

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If its a PCP&C unit... yes, you will be fineThe trick with PSU's past their "Watt" and "Amp" rating game and "Multiple Rail" game is the Efficiency ratingSince that unit as I recall has a 82-85% EFF rating you are definitely good to go. It will actually peak at around 800-840 if I remember the specs on that one correctly. Its not duty cycle rated for that 800+watt load but it will peak under high stress without failureYou get what you pay forThe older PCP&C 750 does not come with the 6+8 pin ATI PCIe plugs but their newer version does. You should get the adapter with the x2 card. ..and do make sure they are both connected.That online calculator tends to display power needs by a 15-20% overhead margin. Make sure you did not miss anything in its list because it can thow off the estimate very easily the way that page is designed. It is a decent estimate since it does take into account overhead but they do not post that.On my systems, system A show a 748W PSU is needed and system B requires 925. Both of those are about 20% higher (including a 5% margin of overhead) than I actually need but I do use a 750 in system A and a 1000w unit in system B none the less. You never know when a upgrade may push that over the top and you always want to keep at least 10-15% in reserve for overhead. The system runs much cooler that way.I skip the capacitor age estimate on that page because the PCP&C units I use have duty rated caps for the life of the unit.you get what you pay for;-)

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Thank you for your thoughts Nick. I have a nice UPS now too. Any predictions on whether ATI 4870 cards will do better in FSX with driver revisions, or do you think this is unlikely?QX9650 w/ Retail HSF|ASUS P5E3 Premium WiFi|4GB Muskin Ascent 7-6-6-18 1T DDR3-1600|EVGA 8800GT|Seagate SATA 2 x 2|Seagate Cheetah 15K.x|XP Pro SP2|Vista 64--maybe never to be installed

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