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A64 NF4 and NF3 Power Supply Requirements: Amps and Split Rails


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OK, time for a serious discussion:

 

Many of you are having basic overclocking issues. Most blame their memory, or the board, when if you have not recently invested in a PSU it is most likely the problem.

 

YOU NEED A 24 PIN PSU TO MAKE THE NF4 BOARD WORK PROPERLY! Epspecially with the 5v memory option. No discussion on this.

 

If you have an overloaded 12v rail with less than the 25A that DFI recommends, don't even attempt to overclock. You will have CPU errors that cannot be fixed by upping the voltage. The memory controller is on the CPU for A64 and "starving" it for power results in not only CPU errors, but also memory controller errors. Forget the NF2 and Intel chipset logic in terms of your PSU and power requirements. It does not apply here. A64 is a completey different animal.

 

What kind of PSU and how many watts/amps are really required?

 

You must have a 24 pin for the NF4 board.

 

I will use the OCZ Powerstream PSU's as and example. I am not saying you need to buy an OCZ PSU, but they are an option. There are many good (and bad) PSU's out there.

 

The OCZ 520W Powerstream has 28A 3.3v, 30A 5v and 33A 12v. Many are using this for overclocking with SLI, even with 2 x 6800 Ultras. This proves to be competely stable. I would recommend being conservative with the 12v accessories (especially cathodes) with 33A on the 12v rail available though.

 

The 600w model has 28A 3.3v, 46A 5v and 20A, 18A on the "split rails" for a combined 38A.

 

Now as for the subject of split 12v rails. IF you loaded all of your gear onto one rail (impossible and I will explain why), then you would have an overload situation. On the OCZ 600w powerstream, the 18A rail is "assigned" to the CPU lead only. The rest of the gear, including the video cards runs off the 20A line. You have 38A available spread over the 2 rails. If you had a less capable PSU with split rails, then loading might be an issue. You would not want 25A split over 2 rails for example.

 

I realize that many do not agree that split rails can work with SLI. I have a DFI SLI rig running 270 x10, for 2700mhz with 2 x 6800 Ultras in the lab. No issues at all, and she is steady as a rock. We have many, many customers running the same, or even higher overclocks with SLI. The fact is that it pretty isolates the CPU from all else as much as possible, which is a good thing. This results in more stable overclocks. Anyone that doubts whether split rails can work has not tried a strong, good quality PSU.

 

I hope this helps many of you out there that are struggling. I am not trying to sell PSU's, just sharing my tech support and personal testing experience with you.

 

Take this info to the bank and withdraw the cash for that new PSU to replace your 18A 12v rail 20 pin overclock blocker. :)

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Thanks... I hope this becomes "sticky" thread material or is integrated into an FAQ...

 

A question though:

Do you know approximately what percentage of the first rails power consumption is used by the CPU, and what percentages are used by all other items on the second rail? how well are they balanced? Your post has certainly alleviated some of my concerns, now I just want to know how much margin I might have (in theory)

 

and since you represent OCZ, can you tell us any parameters we should look for in a power supply that might level the playing field in terms of how they are rated, particularly since we know that not all Power supplies are created equal despite "equivalent" specs? I thought goign by Amps would be safer than just watts, but is there more to look at? is there a standard testing methodology that rates PSUs in a standard way?

 

Thanks again for your post!

 

Edward

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Thanks... I hope this becomes "sticky" thread material or is integrated into an FAQ...

 

A question though:

Do you know approximately what percentage of the first rails power consumption is used by the CPU, and what percentages are used by all other items on the second rail? how well are they balanced? Your post has certainly alleviated some of my concerns, now I just want to know how much margin I might have (in theory)

 

and since you represent OCZ, can you tell us any parameters we should look for in a power supply that might level the playing field in terms of how they are rated, particularly since we know that not all Power supplies are created equal despite "equivalent" specs? I thought goign by Amps would be safer than just watts, but is there more to look at? is there a standard testing methodology that rates PSUs in a standard way?

 

Thanks again for your post!

 

Edward

 

The rails are pretty much discrete. They really don't share power. So given that your CPU has 100% access to the available 18A. All other components share the 20A line.

 

The temperature that a PSU is rated at is a critical factor. Some rate at 30c, some at 40c and some at 50c. Rating at colder temps is bad, since a PSU looses efficiency and power at higher temps. Many so called 500-550w PSU's are really just a decent 350w model, re-rated at a lower temp or most likely just "inflated" to it's new rating.

 

Weight has always been a good indicator of quality. A light case is good. A light PSU is certainly not. Oversized, higher rated components weigh more. Pick some PSU's up at your local super store. Look at the watt ratings and lift. I am certain you will chuckle when you lift some of these "fly weight" units.

 

I weighed 3 PSU's I have laying around. Here is what I got to the nearest 1/2 lb.:

 

300w Sparkle 3.5lbs.

 

430w Enermax 4.0lbs

 

470w OCZ 5.0lbs

 

All of these are or were considered quality units. You can see how weight scales with wattage.

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Here's a link to a thread with a rather large list of recommended PSU's. Also some companies you want to avoid, most of them due to the OEM who made them. Please don't argue over the list here, go there if you disagree with it so if you persuade the knowledgable thread creator otherwise, he'll edit the list.

 

http://www.xtremesystems.org/forums/showthread.php?t=56231

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LOL, that is quite a list in that link. I can't completely agree or disagree, but it's his opinion ann he is entitled to it.

 

I can't engage in that manner of discussion due to the fact that OCZ has the Powerstream and Modstream PSU's on the market. I am glad to see we made the list. :)

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The temperature that a PSU is rated at is a critical factor. Some rate at 30c, some at 40c and some at 50c! Many so called 500-550w PSU's are really just a decent 350w model, rerated at a higher temp or most likely "inflated" to it's new rating.

I think you meant to say "lower temp" since the output of a PSU drops as the temp increases.

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Hi Andy...

 

Now as for the subject of split 12v rails. IF you loaded all of your gear onto one rail (impossible and I will explain why), then you would have an overload situation. On the OCZ 600w powerstream, the 18A rail is "assigned" to the CPU lead only. The rest of the gear, including the video cards runs off the 20A line. You have 38A available spread over the 2 rails. If you had a less capable PSU with split rails, then loading might be an issue. You would not want 25A split over 2 rails for example.
This is why I have and favor this psu.

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Where does the Modstream 520 fall in terms of power and relability with the DFI NF4? Looking at one in the near future.

 

B

 

I have a personal DFI NF4 running a Modstream 520w. I have a single video card and a Winchester CPU running at 2600mhz. I have had issues so far an I have complete stabilty. The 28A on the 12v rail should be good for all single video card applications, For SLI with anything more than 2 x 6600GT, I would suggest something along the lines of the 600w Powerstream.

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