bp9801 Posted August 21, 2015 Posted August 21, 2015 Most likely because the majority of people don't know what their system uses for power, and don't know that they need at least 33A on the +12V rail, and an R9 290X when pushed to it's limits could consume up towards 335W's. I believe that most 750W PSU's will have enough amperage on the +12V rail to power the card, and have enough juice leftover to power the other components in the system, so that's why they recommend it. You could theoretically use a really good 500W PSU (if it fits the 33A on the +12V rail) on a modest Sandy/Ivy/Haswell/Devil'sCanon/Broadwell/Skylake system (which is pretty power efficient). Only 335W? This review puts the stock load number at 386 for the XFX, 397 for the PowerColor. Overclocked puts the XFX up and over 400W. That's the whole system... And do you want to run a system on a PSU that's 75% loaded? Share this post Link to post Share on other sites More sharing options...
El_Capitan Posted August 22, 2015 Posted August 22, 2015 Most likely because the majority of people don't know what their system uses for power, and don't know that they need at least 33A on the +12V rail, and an R9 290X when pushed to it's limits could consume up towards 335W's. I believe that most 750W PSU's will have enough amperage on the +12V rail to power the card, and have enough juice leftover to power the other components in the system, so that's why they recommend it. You could theoretically use a really good 500W PSU (if it fits the 33A on the +12V rail) on a modest Sandy/Ivy/Haswell/Devil'sCanon/Broadwell/Skylake system (which is pretty power efficient). Only 335W? This review puts the stock load number at 386 for the XFX, 397 for the PowerColor. Overclocked puts the XFX up and over 400W. That's the whole system... And do you want to run a system on a PSU that's 75% loaded? Why not? Great PSU's can handle 100% load without a sweat. Besides, the only time a system will get loaded is when you're playing games, as most of the power consumption comes from the graphics card(s). Share this post Link to post Share on other sites More sharing options...
ccokeman Posted August 22, 2015 Posted August 22, 2015 Most likely because the majority of people don't know what their system uses for power, and don't know that they need at least 33A on the +12V rail, and an R9 290X when pushed to it's limits could consume up towards 335W's. I believe that most 750W PSU's will have enough amperage on the +12V rail to power the card, and have enough juice leftover to power the other components in the system, so that's why they recommend it. You could theoretically use a really good 500W PSU (if it fits the 33A on the +12V rail) on a modest Sandy/Ivy/Haswell/Devil'sCanon/Broadwell/Skylake system (which is pretty power efficient). Only 335W? This review puts the stock load number at 386 for the XFX, 397 for the PowerColor. Overclocked puts the XFX up and over 400W. That's the whole system... And do you want to run a system on a PSU that's 75% loaded? Why not? Great PSU's can handle 100% load without a sweat. Besides, the only time a system will get loaded is when you're playing games, as most of the power consumption comes from the graphics card(s). True, That being said GPU manufacturers base the PSU requirement on the card and system not just the card. I ran 3 GTX 260's on a Corsair TX 750 and was pulling close to 850w with the whole system but the PSU just kept chugging along and still powers the computer I built my aunt 4 years ago. Share this post Link to post Share on other sites More sharing options...
Waco Posted August 22, 2015 Posted August 22, 2015 Most likely because the majority of people don't know what their system uses for power, and don't know that they need at least 33A on the +12V rail, and an R9 290X when pushed to it's limits could consume up towards 335W's. I believe that most 750W PSU's will have enough amperage on the +12V rail to power the card, and have enough juice leftover to power the other components in the system, so that's why they recommend it. You could theoretically use a really good 500W PSU (if it fits the 33A on the +12V rail) on a modest Sandy/Ivy/Haswell/Devil'sCanon/Broadwell/Skylake system (which is pretty power efficient).Only 335W? This review puts the stock load number at 386 for the XFX, 397 for the PowerColor. Overclocked puts the XFX up and over 400W. That's the whole system... And do you want to run a system on a PSU that's 75% loaded?Yes. They're most efficient at 80% to 90% load, generally. Share this post Link to post Share on other sites More sharing options...
bp9801 Posted August 22, 2015 Posted August 22, 2015 Most likely because the majority of people don't know what their system uses for power, and don't know that they need at least 33A on the +12V rail, and an R9 290X when pushed to it's limits could consume up towards 335W's. I believe that most 750W PSU's will have enough amperage on the +12V rail to power the card, and have enough juice leftover to power the other components in the system, so that's why they recommend it. You could theoretically use a really good 500W PSU (if it fits the 33A on the +12V rail) on a modest Sandy/Ivy/Haswell/Devil'sCanon/Broadwell/Skylake system (which is pretty power efficient).Only 335W? This review puts the stock load number at 386 for the XFX, 397 for the PowerColor. Overclocked puts the XFX up and over 400W. That's the whole system... And do you want to run a system on a PSU that's 75% loaded?Yes. They're most efficient at 80% to 90% load, generally. True, and like Frank said, what the PSU requirements are listed at is for the whole system. I'd much rather go for a PSU a touch over the requirement because who knows what I'll run in it. So, don't really see why it matters when you said the whole system was pulling it in the review. Share this post Link to post Share on other sites More sharing options...
Waco Posted August 22, 2015 Posted August 22, 2015 The whole system pulled 400 watts..yet the recommendation is 750. Even a decent 450 watt PSU would be fine! Share this post Link to post Share on other sites More sharing options...
bp9801 Posted August 22, 2015 Posted August 22, 2015 The whole system pulled 400 watts..yet the recommendation is 750. Even a decent 450 watt PSU would be fine! Some/most 450Ws can do 36+ amps on the +12V rail, so you'd be OK there, if you don't mind using a Molex connector and adapter for the other 6 or 8-pin cable. Share this post Link to post Share on other sites More sharing options...
ccokeman Posted August 22, 2015 Posted August 22, 2015 You can only push so much power through a card based on the 75w from the PCIe slot and 75w from a 6pin or 150w from an 8 pin PEG connection off the PSU. Although the spec is rated such they can carry more than the rated spec. Total board power is an indicator of what you can expect a card to pull when running in spec. So just for the video card running 1x 6 pin = 150w to the GPU board 1x 8 pin = 225w to the GPU board 1x 6pin and 1x 8 pin = 300w to the GPU board So rated potential + the system config potential gets you to the end of your calculation. so you can figure out just what you need. Bank on the potential of the card and then figure out what you need from there. Share this post Link to post Share on other sites More sharing options...
cchalogamer Posted August 23, 2015 Posted August 23, 2015 Because people tend to buy really crappy power supplies. Simply put Waco answered this one PERFECTLY from the start GPU makers have to market and spec based on the things idiots too lazy to do a little research will buy. Units like this do exist and they might have a hope of outputting 500w so there you go. As for running a PSU @ 75% load...yeah they are designed to do it (well GOOD units are anyway). Minimum I would slap on a 290X/Haswell build would be a 500w to give a little extra breathing room, but you could certainly do less and be fine. Share this post Link to post Share on other sites More sharing options...
Waco Posted August 23, 2015 Posted August 23, 2015 I run power supplies at 90%+ load 24/7 at work. If they're built properly, that's where they'll run happily for years. Share this post Link to post Share on other sites More sharing options...
ccokeman Posted August 24, 2015 Posted August 24, 2015 I run power supplies at 90%+ load 24/7 at work. If they're built properly, that's where they'll run happily for years. I cannot disagree! I did run an 800w Mushkin PSU in my daily rig for years overclocked and running from 2 GTX 580s up to 2 R9 290's running F@H before it finally died..... I shed a tear that day since it was a $150 fix! Share this post Link to post Share on other sites More sharing options...
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