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Powerful enough PSU for ATI 6790?

Discussion in 'How to: Building a PC, Modding, Overclocking' started by hitman47222, Oct 12, 2011.

  1. hitman47222

    hitman47222 Dedicated Member

    Hi , I am currently planning on buying a new video card to replace my out-aged ATI 4730 , I selected ATI 6790 since it seems the best i can get with my budget, Anywayz I was wondering if my PSU can handle it? On ATI 6790 Page it says a 500 Watt or greater power supply is required , I have a GIGABYTE PSU 550P .. Its supposed to have 450 continuous output and 550 Peak combined wattage. here is a link to the PSU GIGABYTE - PC Components - Power Supply - Superb series - Superb 550P , So what i am wondering is whats difference between peak and continuous output ? And do i need a 500 watt continuous output PSU to run the 6790 or i can use mine? I am really low on budget since i am also planning to buy a new CPU .. So i hope i can run it on this.

    Anywayz thanks in advance
  2. Digerati

    Digerati Super Moderator Techie7 Moderator

    It sounds like you would be pushing it with that card, but note those suggested minimums are based on what they think the average user has in his computer (CPU, RAM, number of drives and fans, etc.). You may have more RAM or a more hungry CPU. Here is my canned text on sizing up PSUs.
    Use the eXtreme PSU Calculator Lite to determine the minimum and recommended power supply unit (PSU) requirements. Plan ahead and plug in all the hardware you think you might have in 2 or 3 years (extra drives, bigger or 2nd video card, more RAM, etc.). Be sure to read and heed the notes at the bottom of the calculator page. I recommend setting Capacitor Aging to 30% (see my note below), and if you participate in distributive computing projects (e.g. BOINC or Folding@Home) or extreme 3D animated gaming, I recommend setting both TDP and system load to 100%. These steps ensure the supply has adequate head room for stress free (and perhaps quieter) operation, as well as future hardware demands. Research your video card and pay particular attention to the power supply requirements for your card listed on your video card maker's website. If not listed, check a comparable card (same graphics engine and RAM) from a different maker. The key specifications, in order of importance are:
    1. Current (amperage or amps) on the +12V rail,
    2. Efficiency,
    3. Total wattage.
    Don’t try to save a few dollars by getting a cheap supply! Digital electronics, including CPUs, RAM, and today's advanced graphics cards, need clean, stable power. A good, well chosen supply will provide years of service and upgrade wiggle room. Look for power supply brands listed under the "Good" column of PC Mech's PSU Reference List. Another excellent read is Tom’s Hardware, Who’s Who In Power supplies: Brands, Labels, And OEMs. Note that some case retailers “toss in” a generic or inadequate PSU just to make the case sale. Be prepared to “toss out” that supply for a good one with sufficient power.

    Most PSUs have an efficiency rating of around 70%. This means for every 100 watts of power a PSU draws from the wall, only 70 watts is delivered to the motherboard, with the rest wasted in the form of heat. The best supplies are 85 to 90% efficient, and as expected, cost more. I strongly recommend you pick a quality supply with an efficiency rating equal to or greater than 80%. Look for 80 PLUS and EnergyStar Compliant labels. 80 PLUS PSUs are required to have fairly linear efficiencies. This is important to ensure the PSU is running at or near peak efficiency regardless the load or power demands. Non-linear PSUs typically are most efficient when the load is in a narrow range between 70 and 90% of the PSU’s capacity and the efficiency may drop dramatically above and below those amounts.

    Too big of a PSU hurts nothing but your budget. Your computer will draw from the PSU only what it needs, not what the PSU is capable of delivering. If a computer needs 300 watts it will draw 300 watts regardless if the PSU is a 400W, 650W, or 1000W PSU. In turn, the PSU, regardless its size will draw from the wall only what it needs to support the computer. In this example, it will draw 300 watts, plus another 45 – 90 watts, depending on the PSU’s inefficiency.

    As noted, the eXtreme Calculator determines minimum and recommended requirements. If the calculator (with the changes I suggested) recommends a 400 watt minimum, a quality 400W supply will serve you just fine. However, a quality 550W – 600W supply will have, among other things, larger heat sinks to dissipate potentially more heat. It might have a larger fan too. The 400W supply will run most of the time closer to capacity, while the larger supply will be loafing along, rarely breaking a sweat. To help the smaller heat sinks get rid of the wasted 80 watts (20% of 400) of heat, the fan in the 400W supply may need to run full speed, while the fan in the larger supply, with bigger sinks just loafs along too – but in near silence. Also, it is typical for manufacturers to use higher quality parts, design, and manufacturing techniques in their higher power supplies.

    Note: Capacitor Aging. All electronics “age” over time. Electrons flowing through components bang around and create friction and heat causing wear and tear, altering the electrical characteristics of the device. Over time, this weakens the device resulting in eventual failure. Power supplies have always suffered profoundly from aging effects resulting in a loss of capacity. In recent years, capacitor technologies have improved. The best PSUs use the best (and most expensive) capacitors which suffer less from aging effects than older capacitor types. If planning on buying a new, high-end PSU, setting capacitor aging to 10% may result in a more realistic recommendation. However, headroom “buffer” will be significantly reduced. You can expect your PSU to last 5 years or longer. Since it is better to buy too big rather than too small, and since it is hard to predict what your power requirements will be in 3 years, using 30% for Capacitor Aging ensures you have enough headroom for virtually any upgrade.

    Don't forget to budget for a good UPS with AVR (automatic voltage regulation). Surge and spike protectors are inadequate and little more than fancy, expensive extension cords. ​
  3. hitman47222

    hitman47222 Dedicated Member

    Well on that Calculator , With ATI 6790 Selected and the rest of my specs , It said 249W recommended and 199W minimum , Does that mean i am clear to buy it? Also.. Can you explain whats the difference between continuous output and peak output in a PSU?
  4. Digerati

    Digerati Super Moderator Techie7 Moderator

    That seems low. What are your computer specs?

    It is pretty much what it sounds like. Continuous is what it can "cruise" at, all day long and not over heat, or become unstable. Peak is what it is capable of when you whomp on it - when the CPU and GPU and all your RAM are at maximum utilization and all your drive motors are ramping up. These are the "peak" demand times and typically only last a few seconds at a time - any longer and the PSU will overheat or become unstable and shutdown - causing the computer to hard "crash", which can result in data loss and/or a corrupt hard drive.
  5. hitman47222

    hitman47222 Dedicated Member

    Hmm, Ok.. One last question : I want your advice on this , I am gonna buy it and try it with this PSU ... However what i wanna know is .. What should i expect to see if its not working? I mean aside from crashing when i launch PC , If i boot PC and i find everything is fine .. Can i continue or its a big risk? Also keep in mind that the rest of PC is pretty low on power , I have a dual core and just 3GB Ram , No CD/DVD Rom or any extra PCI Cards , 1 HDD with only 500GB
  6. Digerati

    Digerati Super Moderator Techie7 Moderator

    There's no way to answer that. It there was, troubleshooting computers would be easy.

    A good PSU will shutdown to avoid damage to itself and to the components it powers, if it senses a fault. A stressed PSU can produce unstable and unpredictable, depending on which device is affected most.

    I suspect you will not have any problems. The size of that PSU is fine. I am not familiar with Gigabyte PSUs, but they are my preferred motherboard maker and I have used a few Gigabyte graphics cards (including in my machine I am using now) with no problems. They are a reputable company so I have every reason to expect their PSUs are of equal quality.
    Last edited: Oct 13, 2011
  7. hitman47222

    hitman47222 Dedicated Member

    Alright man, Thanks for the help.