12v rails

Wingfan · September 8, 2014

Ive been told for awhile that a single 12v rail is the best way to go. My question is mine (EVGA NEX750B) has 4 each with 20a. Is this going to present any problems for me? I plan on Crossfireing in the near future.

Thanks for any help/suggestions

PS I got it for $39.99, one of the main reasons for the purchase

quan289 · September 8, 2014

The NEX750B isn't particularly a good PSU, but for $39.99, it's not badly priced.

The purpose of multi-rail is to provide any extra layer of protection in an event of a component drawing too much power off of a single connector. Single rail doesn't have this protection, so it can theoretically draw the entirety of its 12v off of a single connector. In this case, the NEX750B limit up to 20A per 12v rail (240w) - a little higher as the OCP is typically set higher than what it is rated for. For a single card, it likely isn't going to caused a problem, as if there's any shut down due to the OCP setting off, you could run the GPU off of one connector on the 12v2 and another on the 12v4 rail which leaves you effectively up to 40A for your GPU.

However, certain GPUs in certain crossfire situation, the rather low OCP trip point may cause some problems for you. For example, this R90x Lightning from MSI can draw up to nearly 300w peak during gaming load. As I have stated, the OCP is typically set higher, so you may be able to run one of these cards per rail; however, during Furmark, it nearly got up to 400w load which would likely trip the OCP. Also, if you were to overclock the GPU with increased voltages, that too may cause the OCP to set off.

This is why a single rail may be ideal for some people. Of course, you could get a better quality MR that is capable of supply that setup while still having that benefit of safety such as the Antec HCP-850 Platinum (which is a rather expensive premium power supply).

Either way, even if the NEX750B was a single rail, being an entry level power supply, I wouldn't used it for such a high-end setup.

Wingfan · September 9, 2014

The NEX750B isn't particularly a good PSU, but for $39.99, it's not badly priced.

The purpose of multi-rail is to provide any extra layer of protection in an event of a component drawing too much power off of a single connector. Single rail doesn't have this protection, so it can theoretically draw the entirety of its 12v off of a single connector. In this case, the NEX750B limit up to 20A per 12v rail (240w) - a little higher as the OCP is typically set higher than what it is rated for. For a single card, it likely isn't going to caused a problem, as if there's any shut down due to the OCP setting off, you could run the GPU off of one connector on the 12v2 and another on the 12v4 rail which leaves you effectively up to 40A for your GPU.

However, certain GPUs in certain crossfire situation, the rather low OCP trip point may cause some problems for you. For example, this R90x Lightning from MSI can draw up to nearly 300w peak during gaming load. As I have stated, the OCP is typically set higher, so you may be able to run one of these cards per rail; however, during Furmark, it nearly got up to 400w load which would likely trip the OCP. Also, if you were to overclock the GPU with increased voltages, that too may cause the OCP to set off.

This is why a single rail may be ideal for some people. Of course, you could get a better quality MR that is capable of supply that setup while still having that benefit of safety such as the Antec HCP-850 Platinum (which is a rather expensive premium power supply).

Either way, even if the NEX750B was a single rail, being an entry level power supply, I wouldn't used it for such a high-end setup.

Thanks for the info

As of right now this is what im using it for:

G3258 4.5GHz

MSI Z97M Gaming

PowerColor R9 280

G. Skill Sniper 8GB

So for what i have its good, but probably not for when I upgrade to a 2nd 280 and a 4790K?