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HX or TX series PSU for my power hungry GPU?


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Forgive that newbie question ...


Dear friends, power supplies like the HX620W uses independent triple +12V power rails, each supporting 18A. According Sapphire's technical specification, my Radeon HD-3850 *AGP* needs a +12V rail supporting 30A through two molex connectors. Can I power this GPU with a power supply like the HX620W or I must buy a TX series power supply with single +12V rail but with higher amps in that rail?


In other words, how a HX series PSU handle a GPU that needs more than 18A in the +12V rail?

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  • Corsair Employees

The HX series supplies are actually single rail, the only true multi-rail PSU that we have is the HX1000 which has 2x 12v rails each rated at 50A. The HX620 has a single 12v rail rated at 50A. Here is a quote from PowerGuy explaining why the HX620 and HX520 were originally advertised as triple rail.


Taken from HERE:


The answer is no to each of these, as the PSU is actually a single-rail design.


The reason for this confusion is due to the ATX specification changes from ATX 2.0 to ATX 2.2.


At one point there was a 240va limitation per output, which meant any PSU with more than 20A of +12V output would have to have multiple "rails". As these weren't usually separate +12V sources, they were typically just separate OCP points on each physical trace, thus creating a 20A OCP point on 2 or 3 or 4 or 6 or however many "rails" were in the design.


As we were designing the product, the ATX spec changed from the 240va limitation being a requirement to being merely a recommendation, but we already had packaging, manuals, and labels finished and a significant amount of money in them. The decision was made to change the PSUs functionality so that it only had one "rail", but to leave the specs as they were so we wouldn't take a huge loss of money on packaging and such.


It's a bit confusing but for most users it does not matter. For our customers who want to know (those who read forums or email us) we will answer honestly. It's spec'd as a 3-rail design but functions as a single-rail design.


There is a single OCP/OVP point, a single +12V source inside the HX520/HX620 supplies.

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