Update! Quick Question regarding PSU for A8N-SLI

[jdogg707]

Well, I have decided to upgrade to two video cards using the system in my sig. I have one 6800GT and just got through buying another. After reading all the debate about Dual Rail PSU's, I decided to sell my Enermax 600W Noisetaker, and get a good single rail PSU for my SLI setup. After doing a good bit of digging, I have narrowed my selection down to two:

PC Power and Cooling 510 SLI and OCZ PowerStream 520

The PCP&C has 38A on the 12V rail, while the OCZ has 33A. The PCP&C has two PCI Express connetors, while the OCZ has only one. Both has 24 Pin support, and both have more than enough leads for the devices I will be connecting to it. I have heard PCP&C PSU's have dead-on rails, while the OCZ has adjustable rails. The big deciding factor here is cost, the OCZ is 146.99 shipped, while the PCP&C is 250.95 shipped. Please let me know what you guys think! I want stability from this PSU and no issues with the SLI, plus maybe an extra hard drive or two added down the line.

Thanks for the input!


Updated:

I finally got my second card and installed it with my current PSU. I am a little worried about the rails that I got under one run of 3DMark03, 12V - 11.68, 5V - 5.053, 3.3V - 3.216. The system hasn't suffered from any problems, and completed the run, but those looks extremely low to me. What do you guys think?

 

[FastEddie]

Either of those would suit you in spades. So would an Antec True 550 12vEPS for alot cheaper.

 

[Vtach]

I have the antech 550 np so far...

 

[jdogg707]

Ok, so you guys arel iking the 12vEPS, does it has PCI Express support?

 

[Algere]

Originally posted by: jdogg707
Well, I have decided to upgrade to two video cards using the system in my sig. I have one 6800GT and just got through buying another. After reading all the debate about Dual Rail PSU's, I decided to sell my Enermax 600W Noisetaker, and get a good single rail PSU for my SLI setup.

:roll: If the 600W Noisetaker was lacking, makes you wonder why VoodooPC would use a 600W Noisetaker as their preferred PSU for their custom configured SLI rigs.

 

[jdogg707]

Thanks for the info! I am going to get my SLI combo and see what happens when I add another card. I might not be buying another PSU at all! My current rails are 11.904 on the 12V, 5.026 5V, and 3.248 on the 3.3V. I think I'll go with the Powerstream if I do replace it, because I just can't see spending that $250 on a PSU right now.

 

[Algere]

Alright, here's what I've gathered.

The 600W Noisetaker 2.0 has a 18A max limt per +12V rail & a combined 35A total shared between the 2. Pretty much means that if one rail were to utilize 18A, there would be 17A left on the other rail, or if 16A were used on one rail, the other rail would have 16A to use - whatever combination totaling 35A.

I just had a interesting "chat" in another thread with F4810 and what I've or we found out in comparison to a PSU like the Neopower is...

Antec Neopower
RAIL 1/18A powers... everything else that uses +12V
RAIL 2/15A powers... CPU only


Enermax Noisetaker v2.0
RAIL 1/18A max. powers... PCIe, 4-pin peripherals (hard drive, optical, etc.), & 3-pin peripherals (floppy)
RAIL 2/18A max. powers... MB, CPU, & SATA

As you can see, on top of the ability to share amps between the rails. The Enermax has better distribution of what components are connected to what rail.


EDIT: Errored when I said 16A on 1 rail gives you 16A on another rail. Clearly 16+16 doesn't equal 35A. I was thinking about the specifications of the 32A total on the 485W Noisetaker in my head.

 

[FastEddie]

Originally posted by: jdogg707
Ok, so you guys arel iking the 12vEPS, does it has PCI Express support?

You don't need to have PCI-E support as an adapter will do just fine. You are going to spend about $100 more for those bells and whistles that you really don't need.

And I've been explaining for days the current dual rail psu's on the market aren't designed for SLI boards, regardless of marketing label is slapped on the box. Get a single rail psu that supplies around 24amp or better on the 12v rail, and you'll be there in spades.


Read this thread for an indepth discussion on the subject, after the initial garbage--->
Dual Rail PSU

 

[jdogg707]

Originally posted by: FastEddie

Originally posted by: jdogg707
Ok, so you guys arel iking the 12vEPS, does it has PCI Express support?

You don't need to have PCI-E support as an adapter will do just fine. You are going to spend about $100 more for those bells and whistles that you really don't need.

And I've been explaining for days the current dual rail psu's on the market aren't designed for SLI boards, regardless of marketing label is slapped on the box. Get a single rail psu that supplies around 24amp or better on the 12v rail, and you'll be there in spades.


Read this thread for an indepth discussion on the subject, after the initial garbage--->
Dual Rail PSU

That thread is the reason I am looking to switch my current PSU. I'll see what happens with my two GT's once they get here and will reassess from there.

 

[Algere]

Originally posted by: FastEddie

Originally posted by: jdogg707
Ok, so you guys arel iking the 12vEPS, does it has PCI Express support?

You don't need to have PCI-E support as an adapter will do just fine. You are going to spend about $100 more for those bells and whistles that you really don't need.

And I've been explaining for days the current dual rail psu's on the market aren't designed for SLI boards, regardless of marketing label is slapped on the box. Get a single rail psu that supplies around 24amp or better on the 12v rail, and you'll be there in spades.


Read this thread for an indepth discussion on the subject, after the initial garbage--->
Dual Rail PSU

On another thread some have run fine with dual rails & SLI. I believe that when the Antec Neopower e.g. & power supplies with similar +12V distribution designs were released, they weren't released with dual PCIe requirements in mind and from the implementation that one rail is entirely dedicated to powering the CPU. One can assume Antec (& others if applicable) anticipated that CPU power requirements (e.g. Prescott & future CPU's in mind) would soar way passed the power requirements that a single video card would need, which is true IMO.

Also if VoodooPC offered the dual railed 600W/18A per rail Noisetaker as the only PSU option for their SLI rigs, wouldn't one believe they would've tested it prior to offering it as an option?

 

[Algere]

In addition, purely speculation but not impossible of course but what if...

When single rail PSUs have their actual rated +12V amps maxed out, it would cause stability issues/fluctuations since their amp rating is really high ergo not able to utilize all of the rated amps stably. In contrast, since dual rails don't have such a high amp rating per rail , it can utilize more if not all of it's rated amps without stability issues arising.

Assuming of course the higher the amp rating on a rail, the higher the chance stability will fail on that rail & in turn, overall system failure.

 

[FastEddie]

Algere--VoodooPC would have better served the buyer with a single rail unit. Both rails on dual rail psu's are fixed, where the 12v AUX connector (one rail) will never max 15a let alone the 18a found on the 600W Noisetaker, the second rail could, not will, but could. My point is that none of these SLI labeled psu have really been designed for these SLI boards. It's just a marketing ploy. These units were made for Intel PCI-E systems, and some (with the 24-pin 12vEPS power connector) have been rated for multi-processor boards. But they are limited because of such a low amp rating on both rails.

 

[Algere]

Originally posted by: FastEddie
Algere--VoodooPC would have better served the buyer with a single rail unit. Both rails on dual rail psu's are fixed, where the 12v AUX connector (one rail) will never max 15a let alone the 18a found on the 600W Noisetaker, the second rail could, not will, but could. My point is that none of these SLI labeled psu have really been designed for these SLI boards. It's just a marketing ploy. These units were made for Intel PCI-E systems, and some (with the 24-pin 12vEPS power connector) have been rated for multi-processor boards. But they are limited because of such a low amp rating on both rails.

First of all, you're assuming 15A for a CPU (+12V 4-pin aux.) isn't possible for tommorow's CPU, with dual core & what not coming, I don't see how can't you see it not consuming alot of power & secondly the 18A rail on the Enermax doesn't just power the CPU, it powers the MB & SATA drives as well.

Hence this...

Source (Enermax Noisetaker 2.0 +12V distribution specs)
Source (Antec Neopower +12V distribution specs; last page)

Antec Neopower
RAIL 1/18A powers... everything else that uses +12V
RAIL 2/15A powers... CPU only


Enermax Noisetaker v2.0
RAIL 1/18A max. powers... PCIe, 4-pin peripherals (hard drive, optical, etc.), & 3-pin (floppy)
RAIL 2/18A max. powers... MB, CPU, & SATA

With the Neopower, the CPU gets it's own rail which is more than enough for now. The problem with the Neopower's design is that every other +12V dependant component vies for power on the other rail. Not the case with the Enermax (as shown above). The way Enermax has implemented it's dual rail design allows half (roughly) of the load of the entire system to be powered by one +12V rail while the other half of the load is powered by the other rail. The shared amp feature allows flexibility in that if one rail needs more amps than the other, it can borrow from the other rail.

e.g. CPU = rail 1 / video card(s) = rail 2

Dual Core CPU > single video card
For argument sake we'll say the dual core CPU sucks more power than a single video card. You'd want more amps on rail 1 then 2. Amp sharing allows you to take some amps from rail 2 that isn't fully utilized by the video card and distribute it onto rail 1 - the rail the CPU is using.

Dual video cards (SLI) > Single Core CPU
This scenario, the dual card SLI implementation would require more juice than the single core CPU. Then you'd want to borrow the unused amps from the CPU's rail 1 and give the unused amps to power up the SLI'd cards on rail 2.

 

[FastEddie]

Algere--You're right. I didn't even think of dual core, which is purported ro work out of the box on the A8N SLI. Man, I would be unloading those wimpy dual rail psu's quick.

I agree. Now the 12v AUX connector (one single rail) is plenty to run the processor and trace lengths from the dimm sockets to the cpu. That line won't get maxed (might with dual core), it's the second 12v rail. Yes, 18a is pretty decent. Buts it's like always driving your car, every time you put the key in and start it, with your foot to the floor. I'll note this one more time---you don't want to run a psu at or close to 100% of it's ability!

 

[Algere]

I believe when Antec released the Neopower around mid '04 or about. They probably had the idea that future CPU's would be dual cored & suck up lots of power and there wouldn't be any dual video card systems (SLI) out. Which I can assume is probably the design behind the Neopower (more power to CPU, less to other components) which is fine for non-SLI systems IMO.

Fast forward to late '04 and SLI arrives on the scene & PSU specs are required to change as the Neopower doesn't have enough power to power 2 gfx cards on one single rail as you've said.

I'll note this one more time---you don't want to run a psu at or close to 100% of it's ability!

Amen

 

[Vtach]

Ok you think my performence of my set up or lack of is due to my antech 550 and not enough power for my ps, with the 20 pin connector?
ie amd fx55 bfg 6800gt 1 gig carsair 550 xms <single card only atm> or you think its a bios issue?
I have orederd the thermake take adapter

 

[jdogg707]

Update at top!

 

[Algere]

Is that a BIOS reading?

Anyways FWIW the +12V & 3.3V line is within 3%. Anything within the preferred +/- 5% margin is good enough.

 

[jdogg707]

Originally posted by: Algere
Is that a BIOS reading?

Anyways FWIW the +12V & 3.3V line is within 3%. Anything within the preferred +/- 5% margin is good enough.

No, not a BIOS reading, but an Asus Probe reading. I have found that the readings in Asus Probe and the BIOS are extremely similar. As long as those readings aren't low, I think I'll probably keep what I have for a bit longer.

 

[scruffles]

for anyone who is wondering if the stock psu thta comes with the antec 350 watt case will work, it does! though i'm only running one graphics card for now.

3500+ 64, stock fan, asus sli board, 10000 raptor 74 gig, 1 gig corsair value, and Chaintec 6600gt

all on stock 350 antec smart power psu.

 

[Algere]

Originally posted by: jdogg707

Originally posted by: Algere
Is that a BIOS reading?

Anyways FWIW the +12V & 3.3V line is within 3%. Anything within the preferred +/- 5% margin is good enough.

No, not a BIOS reading, but an Asus Probe reading. I have found that the readings in Asus Probe and the BIOS are extremely similar. As long as those readings aren't low, I think I'll probably keep what I have for a bit longer.

The voltages are good enough IMO (I guess I already said that ), they're similar to the Neopower's* low +12V rails - albeit within safety range, from reviews I've seen.




*Not obsessed with the Neopower, just a point of reference since it's a popular dual rail PSU model. :thumbsup:

 

[Algere]

If it eases your mind a bit & IIRC I think it's required to be within 10%.