SLI GTX GeForce 660 DCII OC & PSU Requirements

This is a semi-difficult question to ask because for one, I think I already know the answer, and two, I am not sure where to post this question precisely, either way, I am hoping that someone who is more apt than I is able to answer this question thoroughly.

My Scenario

I had just received a second ASUS GeForce GTX 660 DirectCUII OC, for three reasons. One, I had just upgraded my motherboard to an ASUS Sabertooth 990FX R2.0 which allows two graphic cards to run in SLI (or CrossFire) in two PCIe 3.0 x16 slots. Two, because after searching for 2 months for an ASUS GeForce GTX 560 DCII OC (my previous card) and getting burned by an eBay reseller I discovered that the ‘ASUS GeForce GTX 560 DCII OC’ are pretty much impossible to find, even though I had purchased mine only a year ago. Lastly three, I loved my original ASUS GeForce GTX 560 DCII OC so much (mostly because it idled at an impressive 30c to 60c ‘<- under load’) that when I decided to upgrade, I decided to go with a better model of what I already had.

I have never ran an SLI and/or a CrossFire rig before, and I am doing this partly for performance reasons, partly for curiosity and experimental reasons, and partly to play next gen games for another few years without worrying whether my graphics card will be up to the task. I have built 5 personal rigs, and maybe 20 plus personal computers for work and other people within the last 19 years or so, and although I would not say that I am an ‘expert’ when it comes to developing a well-balanced and stable PC, I am pretty familiar with how computers operate internally. My question is a multi-part one, and I am hoping to get some feedback from some veteran gamers who have ‘currently’ built an SLI rig, with ‘modern’ components. I am fully aware of all of the pros and cons of configuring a rig like this (i.e.: micro-stuttering, drivers, scaling, etc…), however, technology evolves fast, and what one might have experienced a few years ago generally should not be compared with the type of results that you might expect with today’s technology. With that said, here is my issue.

My Setup

Currently I am running a well-balanced system, and everything runs peachy keen. Here are my specs so that you may get a better idea of what I am working with:

• (MoBo) ASUS Sabertooth 990FX R2.0
• (CPU) AMD FX-8120 Zambezi 32nm
• (RAM) Kingston HyperX DDR3-1600 – 9-9-9-24 – (4 x 4GB = 16GB)
• (GPU) ASUS GeForce GTX 660 DirectCUII OC
• (HD) Seagate Barracuda SATAII 932GB
• (LCU) Corsiar Hydro Series H100 Liquid CPU Cooler
• (FAN) Kingston HyperX Internal Fan (For RAM)
• (FAN) Thermaltake TMG SLI 80mm Dual PCI Slot Cooler
• (FAN) Cooler Master 140mm
• (FAN) Enermax UCMA12 120mm
• (FAN) TriCool 140mm x 2
• (FAN) Generic 140mm x 2

• (PSU) Thermaltake R2 600W ATX 12V 2.3

Note: in addition, I have DOCP enabled on my motherboard to regulate my CPU, RAM, and NB frequencies, which also shifts the voltages being used on these components.

My Problem

Everything is currently running off of a Thermaltake R2 600W ATX 12V 2.3 PSU right now, and I am wondering whether I “can/should” install (and SLI) my secondary GPU (ASUS GeForce GTX 660 DCII OC), or upgrade my PSU first. Now, I have already calculated what sort of draw (or how many Watts) I would generally need to run my current rig (including my rig with an additional GPU in SLI), using eXtreme Power Supply Calculator Lite, ASUS Power Supply Wattage Calculator, and newegg’s Power Supply calculator with mixed results. In addition, all three of these websites push you to purchase PSU’s, therefore, one can only wonder how accurate these calculators are, seeing as though each website obtains some level of earnings from either directly purchasing a PSU through their web-service, or clicking on advertisements. Moreover, I have personally calculated the draw from each of my components (with a few exceptions), and from what I can tell, I ‘should’ be able to install my secondary card, run it in SLI, and be fine, however, I do not know this for sure, and I do not want to risk plausibly damaging a component or two. Here is what I have calculated for each component, which is derived from manuals and official websites:

• (MoBo) ASUS Sabertooth 990FX R2.0 [ ??? ] <= Cannot Find
• (CPU) AMD FX-8120 Zambezi 32nm [ 125w ]
• (RAM) Kingston HyperX DDR3-1600 – 9-9-9-24 – (4 x 4GB = 16GB) [ 6.3w ]
• (GPU) ASUS GeForce GTX 660 DirectCUII OC [ 150w ]
• (HD) Seagate Barracuda SATAII 932GB [ 24w ]
• (DVDR) ASUS DRW-24B ATA [ 20w ] <= (No Official Source / Approximate)
• (LCU) Corsiar Hydro Series H100 Liquid CPU Cooler [ 8.4w ]
• (FAN) Kingston HyperX Internal Fan (For RAM) [ 1.08w ]
• (FAN) Thermaltake TMG SLI 80mm Dual PCI Slot Cooler [ 4.8w ]
• (FAN) Cooler Master 140mm [ 1.68w ]
• (FAN) Enermax UCMA12 120mm [ 4.08w ]
• (FAN) TriCool 140mm x 2 [ 4.8w ]
• (FAN) Generic 140mm x 2 [ 8.4w ] <= (No Official Source / Approximate)

• TOTAL: 373.54w

• (MoBo) ASUS Sabertooth 990FX R2.0 [ 15 ] <= (No Official Source / Approximate)
• (CPU) AMD FX-8120 Zambezi 32nm [ 170w ]
• (RAM) Kingston HyperX DDR3-1600 – 9-9-9-24 – (4 x 4GB = 16GB) [ 9.6w ]
• (GPU) ASUS GeForce GTX 660 DirectCUII OC [ 150w ]
• (HD) Seagate Barracuda SATAII 932GB [ 30w ]
• (DVDR) ASUS DRW-24B ATA [ 30w ] <= (No Official Source / Approximate)
• (LCU) Corsiar Hydro Series H100 Liquid CPU Cooler [ 8.4w ]
• (FAN) Kingston HyperX Internal Fan (For RAM) [ 1.215w ]
• (FAN) Thermaltake TMG SLI 80mm Dual PCI Slot Cooler [ 4.8w ]
• (FAN) Cooler Master 140mm [ 1.68w ]
• (FAN) Enermax UCMA12 120mm [ 4.08w ]
• (FAN) TriCool 140mm x 2 [ 5.8w ]
• (FAN) Generic 140mm x 2 [ 14.4w ] <= (No Official Source / Approximate)

• TOTAL: 444.96w

Add the second card, and I get the following totals:

Minimum: 523.54
Maximum: 594.96

Now, by looking at the maximum value, I myself agree that it would probably be within my best interest to upgrade my PSU before I attempt to SLI an additional GPU, however, some of these ‘power consumption’ values are rounded up, or estimated on the high-end. In other words, I could have more headroom with my current PSU than I am calculating. Most of these “approximate” values are based on the highest possible values for these components, in an attempt to ensure that I am not under calculating.

I am only asking this question because, currently, I do not necessarily have the funds to purchase a new PSU, and this GPU is simply sitting behind my desk, collecting dust. In addition, I have found a few discussion posts (some within Tom’s Hardware) stating that one should be able to run either SLI and/or CrossFire on a 600W PSU. Any professional opinions regarding this matter would surely be appreciated, and I thank you for your time.
2 answers Last reply
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  1. i am one to always error on the side caution instead pushing a PSU to hard. I would wait. It should work yes but is it worth risking your whole system on the chance it doesn't and fries it or just kills your system earlier then it should from over taxing the PSU. Plus with a older PSU capacitor wear may have already decreased your units capability.
  2. Yes, atomicWar, I am appreciative for the fact that you were able to respond to my post within a quick and friendly manner, although, I am looking for some more ‘in-depth’ input upon this matter. I too (for the most part) do not attempt to overly stress any of my components (including my PSU), however, that is my own personal preference, not a thorough account upon what sort of ‘pros and cons’ one could expect if they were to plausibly push a component close to its maximum potential. Which, in this case, is a 600W PSU. With that said, maybe I should reiterate my question.

    As mentioned, “I am hoping to get some feedback from some veteran gamers, who have ‘currently’ built an SLI rig with ‘modern’ components.” In addition, I am ‘hoping’ to get an ‘in-depth’ and/or ‘detailed’ take on what I can expect if I were to push my PSU close to its maximum potential. While also keeping in mind that I have calculated (to the best of my ability) the maximum draw that I would need from my PSU (if I were to SLI the two GPUs mentioned above) with 5.04 to 76.46 of available output (watts) to spare. Moreover, I do not see how I could potentially ‘overload’ any of my components if I were to ‘max’ out my PSU, seeing as though PSUs are generally designed to only supply a specific quantity of output, and no more. For example, if I were to connect a small list of components and/or devices to my current PSU, and these components and/or devices required more voltage, amperage, and/or wattage than my current PSU could supply, I do not see why these components would simply not function, why my PSU will not shut off due to OCP or OPP being trigger, and why I could be potentially “risking my whole system”.

    I am definitely not an electrical engineer, however, I cannot quite wrap my head around the idea of overloading any of my components if my PSU can only supply a specific level of power, and is a high-quality Thermaltake. Power Supply Units are one of the many components that I ‘do not skimp on’, because I know that if I were to purchase an inferior PSU, I could ‘then’ be exposing my system to potential electrical risks. I have blown fuses from PSUs in the past, years ago, after around 2 years (or so) of use, and this was mainly brought on by the fact that (at one point) I was ‘maxing out’ my PSUs, because I thought that neon lights looked cool within side my computer case. I was a teenager at the time, what do you expect. Anyways, at the time that this happened, I either replaced the fuse or simply replaced my PSU and everything was back in order. I do not see how the same could not potentially occur if I attempt to draw close to my current PSUs maximum level of output, with approximately 5.04 to 76.46 of watts to spare.

    I want to stress the fact that I simply want to be ‘informed’ upon the whys and how something like this could and/or could not work. I appreciate anybody who has their own ‘personal preference’ and/or their own ‘opinion’ regarding this matter, however, I am looking for a more detailed and/or educated response towards my question. I do not mean any disrespect towards anyone who likes to run/operate their system a certain way, however, I am looking for individuals who are (or have) invested their time in understanding how a scenario similar to this could play out, ‘thoroughly’. Thanks in advance towards anybody who is able to assist me with this matter. I will probably end up purchasing a new PSU, even though I am looking at dumping around $130 USD (minimum) on a decent PSU, however, I am still interested in hearing from some ‘experienced’ users in regards to this matter. To see if, first), I am able to do this, second), what to expect if I do this, third), to receive thorough and/or semi-thorough explanations upon what to expect if I do this, and fourth), to better understand the ‘modern’ relationship with Power Supply Units and the components in which they are powering. Thanks again in advance.
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