What Makes a PSU SLI Compatible? Got Answers Here!

[Algere]

Originally posted by: GuitarDaddy
I have worked with 2 guys on two seperate threads lately in the CPU/overclocking forum using the Enermax 600 with 18a and 17a rails. In both cases their boards run fine with a single midrange GPU at stock speeds, but they can't raise HTT over 230-235 even with the CPU and RAM underclocked without hard crashing.

That tells me the rail suppling the mobo is running at max capacity, and when you try and increase HTT, the increased power required by the chipset overloads the power supply

Is it possible to set the PCIe 16X slot to run in 8X mode via BIOS with that one video card? If so and the motherboard follows power consumption specs of 8X PCIe, that should give them an extra 2-3A to play around with on that rail (CPU, MB, & SATA).

P.S. If possible have them set the other unused PCIe 16X slot to 1X unless it's already set to 1X. IIRC 1X = 0.5A, 2X = 1A, 4/8X = 2.1A, & 16X = 4.4~5.5A of 12V power.

Update: Possibly against your findings : see here. OC'd A64 @ 2.6 GHz & dual 6800 GTs goin' solid.

 

[TantrumusMaximus]

Originally posted by: FastEddie

Originally posted by: Algere

I feel like a broken record for saying this but check Falcon Northwest & VoodooPC. They both use that exact PSU (not exact; active PFC, other regular) for SLI systems. Assuming you believe they test those PSUs before making it an available option for such configurations.

Because someone else is using these in their builds doesn't justify the argument that dual rail psu's are perfectly fine to use in SLI builds. That's a cyclic response. That's like saying, Because Ford uses these tires, these tires are good. It's meaningless in any functional argument.

Agreed however Falcon Northwest isn't Ford. They are more like Porsche or Lotus. They don't build CRAP.

 

[jelliott]

My OCZ 600 has been running my system flawlessly.

 

[ribbon13]

Knowing electronics makes PSUs seem so much less complicated.

 

[FastEddie]

Originally posted by: jelliott
My OCZ 600 has been running my system flawlessly.

You're one of the lucky ones. Have you tried any oc'ing?

 

[jelliott]

sure have... only to see if it would run.. but since im no overclocker, its not OC'ed now.

cpu was 2.4 vid cards were 400/1100

maybe i have a freak of nature? lol

 

[FastEddie]

I've noted one other user that had no problems at stock, but would bsod when trying to oc. Which is why I asked.

 

[jelliott]

i dont doubt people are having problems... MAYBE what should be done is list the problematic PSU's.. or a lit of PSU's that work fine .. MAYBE all dual rail PSU's are not all alike... dunno..
but several people are running this same psu and oc'ing to the moon with ultras... :shrugs:

 

[Robor]

Originally posted by: Insomniak

Originally posted by: McArra
TT purepower 680W is also supposed to be for SLI setups and has 3 12V rails, 2 of them with 15A and another one with 8A, for a total of 38A. This is the PSU I will receive next week, is supposed to be really really powerful. I'm not using SLI though, I'm an AGP owner.

Amps still aren't additive - if any of your devices need more than 15A, like an A8N-SLI Deluxe, then you're boned.

This is the PS I purchased for my A8N. It's not a "dual rail" but actually a "tri rail" as it's got 2 15a 12v and a 3rd 8a 12v. So far it's running rock solid with a A64 3200+ @ 2500 and a single BFG 6800GT OC. At some point I will get another 6800GT and SLI them but until then I don't know if my PS is going to be enough to power them. If it's not I'm going to be pretty pissed. Funny but the TT 680 was advertised as being designed for SLI systems. :disgust: :roll:

 

[destroyerjjbg]

seeing asus power specs for a8n sli it dosnt to be very high

http://usa.asus.com/products/mb/socket939/a8nsli-d/overview.htm#

then i think tt 680w 3 12v rails will be enough u can see power specs to sli rig from nvidia too

http://www.nzone.com/object/nzone_sli_howto.html

"
NVIDIA SLI System Type Minimum Recommended PCI Express Power Supply
High-End: GeForce 6800 Ultra 500-550W, +12V @ 30A
Mid-Range: GeForce 6800 GT or 6800 420-480W, +12V @ 25A
Entry-Level: GeForce 6600 GT 350-420W, +12V @ 20A

If the power supply specifies two 12V windings (i.e. 12V1 and 12V2), then these current numbers can be added together to check against the specifications described above. "

Its look like the amps on double rail psu can be added

i think like algere says double rail psu will be limited by the rails power consumption configurations,that`s in case that amps aren`t addictive but its look like they are.

At any rate u can buy silverstone st65zf with quad 12v rails, but i dunno how it performs

http://www.silverstonetek.com/products-65zf.htm

any link to people with sli rig and overclock to see any double rail psu?

thx

 

[dfinder]

A ha lots to be known... thanks for the collection

 

[Algere]

Its look like the amps on double rail psu can be added

i think like algere says double rail psu will be limited by the rails power consumption configurations,that`s in case that amps aren`t addictive but its look like they are.

Total system power consumption is additive to an extent but that's not the same as when someone may think that it's possible to add the amps of two or more 12V rails together to power up a CPU (single component). That's where the confusion comes from when one says amps are additive while another says different.


For example, if a CPU required 16A of 12V power in total & a 3 rail PSU has the following configuration:

12V1/15A = CPU & motherboard (2x2 4-pin & 24-pin)
12V2/18A = PCIe video card (6-pin)
12V3/15A = Hard drive, fans, optical drive, etc. (3/4-pin)

The PSU comes up short when it comes to the power requirements necessary for the CPU. In that case amps aren't additive. The CPU can't borrow/use 12V power from rail 2 and/or 3 since it's seperate from rail 1.

An exception would be a gfx card that receives 12V from both PCIe slot & power plug because a power plug can be on one rail while a PCIe slot can be powered by another. Therefore amps are additive but they're (12V rails) not physically combined in a sense that one rail combines with another which then forms some kind of super 12V rail which then powers a video card.

 

[DemonSamurai]

I am currently building a new AMD 3500+ computer in a full tower ATX case with a Gigabyte SLI motherboard, dual 6800 GT's and 4 SATA drives. The good news, I suppose, is that I have no intention of overclocking any of my components. My goal is to build a system that is both fast and very quiet. I have been leaning toward the Enermax Noisetaker EG701AX-VE SFMA 2.0 SLI (600W). Another big contender is the Antec NeoPower 480 (480W) ATX12V v2.0 due to its modular setup to improve airflow and a single (quiet) 120mm fan. Both have +12V1 at 18A, but the Antec +12V2 is only 15A and not at 18A like the Enermax.

The Turbo-Cool 850 ETX (SSI) mentioned in this thread is an honorable mention, but I understand that when it becomes available next month, its price will be in the $400-$500 range. Too much money for me.

A lot of people, here and other forums, seem to like the OCZ power supplies. Looking at the manufacturers web site, I don't see where these power supplies have enough connectors for (4) SATA drives. I'm I wrong? Also a consideration is the length of the cables since I have purchased a full tower ATX case. The OCZ ModStream power supply cabling appear short.

Any suggestions/recommendations? This is no attempt to hijack the thread. It just seems the perfect place to ask.

 

[Algere]

Wouldn't get the Neopower for SLI. It's basically a 24A 12V PSU when you count up the amps based on your intended setup. The 15A rail powers the CPU only & the other 18A rail powers everything else that uses 12V. Keeping that in mind, it's been said that the A64 Winchesters consume around 6A of power. So combine 6A usable by the CPU on one rail to the 18A available on the other rail.

The Modstream does indeed have short cables or so I've heard so no go there. As far as I'm aware anyways.

The Enermax model by name is aimed towards noise prevention, has better 12V output distribution to prevent wasted amps in contrast to the Neopower - specifics, long cables, SLI compatible (part marketing, part legit), & I'm sure it has at least 4 native SATA connectors (my 485W model has 4 so...).

PCP&C probably has everything you're looking for & in some aspects, more. Except that they're known to be loud PSUs unless it's marketed as being quiet. e.g. Silencer & tend to be a bit on the expensive side. If memory serves the Silencer line isn't a high wattage PSU line so if you're looking for high power & low noise, look elsewhere.

The OCZ 600W Powerstream has a bit more power (2A more on 12V) than the Enermax, but at least to me the length of cable & noise is unknown.

 

[DemonSamurai]

Originally posted by: Algere
Wouldn't get the Neopower for SLI. It's basically a 24A 12V PSU when you count up the amps based on your intended setup. The 15A rail powers the CPU only & the other 18A rail powers everything else that uses 12V. Keeping that in mind, it's been said that the A64 Winchesters consume around 6A of power. So combine 6A usable by the CPU on one rail to the 18A available on the other rail.

The Modstream does indeed have short cables or so I've heard so no go there. As far as I'm aware anyways.

The Enermax model by name is aimed towards noise prevention, has better 12V output distribution to prevent wasted amps in contrast to the Neopower - specifics, long cables, SLI compatible (part marketing, part legit), & I'm sure it has at least 4 native SATA connectors (my 485W model has 4 so...).

PCP&C probably has everything you're looking for & in some aspects, more. Except that they're known to be loud PSUs unless it's marketed as being quiet. e.g. Silencer & tend to be a bit on the expensive side. If memory serves the Silencer line isn't a high wattage PSU line so if you're looking for high power & low noise, look elsewhere.

The OCZ 600W Powerstream has a bit more power (2A more on 12V) than the Enermax, but at least to me the length of cable & noise is unknown.

_______________________________________________________

It sounds like the issue is that dual rails can lead to one of the rails being continuously maxed out or exceeded resulting in a shut down. The rail1 and rail2 current is not additive with the exception of the PCI-Express video cards, if the motherboard & PCI-Express 6-pin connectors are on separate rails. Therefore, many in this forum recommend a single rail power supply. The problem now for me is finding a single rail power supply that can support my developing AMD 3500+ Winchester computer in a full tower ATX case with a Gigabyte SLI motherboard, dual 6800 GT's and 4 SATA drives. Do I chose the Enermax 600W SLI or some single-rail power supply? Any suggestions/recommendations?

And what are your thoughts on the Thermaltake Silent PurePower ATX 12V 2.0 Plus EPS 680W tri-rail or the OCZ PowerStream 520W?

 

[kki000]

I bought the bfg "pwr" bundle with the 2 6800gtpcie and psu.
Boy oh boy was i stunned when i saw it was a dual rai in there, 550w 2x 12v18amps.
I was drawring up my angry letter to bfg with the stats from my a8n manual in hand, how in the world could they package a bundle that was clearly incompatible...

I was all set to ebay the sucker and get a new psu, but i completed the build with the bfg.

Well the 3000+ winchester is running at 2.3 with 255fsb running sli games without a hitch.

from everything ive read, i still wouldnt buy a dual rail psu, but i think they might be viable.

 

[destroyerjjbg]

why the new specs for psu recommend have separate 12v rails ,cause emi and safety, and dont separate 3.3v or 5v rails wich can have equal or more amp than a single psu 12v rail?

well algere i think i have some interesting for u and for the rest,(suppose) the spec rails for the new silverstone quad 12 rails st65zf

Dear Sir:
the Quad +12v support :

+12V1 for CPU1 (8pin)
+12V2 for CPU2 (8pin)
+12V3 for PCI-E & Motherboard (24pin & PCI-E 6pin & M/B 6pin)
+12V4 for HDD & CD-ROM ( 4pin )

So it is no problem to install SLI and overclock your CPU.


Color Titanium black
Cooling System 1x 80mm ball bearing fan
Noise Level 29 dBA minimum
Weigh 2.7 kg
Dimension 150 mm (W) x 86 mm (H) x 180 mm (D)
MTBF 100,000 hours at 25'C, full load
Model Output +3.3V +5V +12V1 +12V2 +12V3 +12V4 -12V 5Vsb
ST65ZF 650W / 710W* 33A 24A 13A/18A* 18A 16A 8A/13A* 0.5A 2.0A

*Peak

i e-mail them too, about the dfi nforce sli havent 8 pin aux in mobo for second cpu , and in the fact didnt have any 8 pin conector ,only the 4 pin aux mobo conector and a 4 pin molex in mobo i dont know for what.
they reply me this

Dear Sir
We have attach a pcs adapter(8pin to 4pin) in the box of SST65ZF.
When your Motherboard is single CPU , you need install this adapter to make 8pin (12v1 & 12v2) to 4pin (12v1)
Thanks


and now i suposse that only 12v1 or 12v2 (this better)can be connected to the mobo.I think they planned this psu compatible with the new intels double core cpus ,that perhaps will have 2 8 pin connectors in mobo for extra power.

but i think that we are wrong with supossing that the elments of a computer only drains for the 12v rail.i think them drains for the 3.3v and 5v rails too and then the plus watagge is extracted for these rails so a psu with double and triple rail is perfectly compatible with a sli rig no super single 12v rail is needed.

 

[DemonSamurai]

The Silverstone Quad +12V rail ST65ZF power supply can be viewed at:

http://www.silverstonetek.com/products-65zf.htm

NOTE: I understand that this quad rail power supplies will begin to be distributed in the U.S. on or about March 5th.

 

[Algere]

It sounds like the issue is that dual rails can lead to one of the rails being continuously maxed out or exceeded resulting in a shut down.

Which is why it's important for PSU manufacturers to design 2+ rail PSUs that distribute a systems entire 12V load evenly throughout the rails, among other improvements.

The rail1 and rail2 current is not additive with the exception of the PCI-Express video cards, if the motherboard & PCI-Express 6-pin connectors are on separate rails.

It's additive cause I was talking about total system power. Both rails power up a system therefore both rails can be added together to determine the requirements necessary for a system's total possible 12V load.

Therefore, many in this forum recommend a single rail power supply.

It's likely they recommend single rail PSUs over a 2 or more rail PSU because...

1) Of ignorance. For instance those that dismiss a PSUs ability just on the fact that it has 2+ rails.
2) It's easier to figure out what amps on what rail powers what on a single rail PSU in comparison to a 2+ rail PSU that powers different things on different rails which isn't the same from PSU to PSU. Differences between 2 & 4 rail PSUs for example.
3) You're likely (not in all cases) to get a little more usable amps with single rail PSUs than with 2+ rail PSUs - depends on PSU & system configurations. Assuming both single & 2+ rail PSUs have the same # of 12V amps in total.
4) Of any combination of 1-3 and/or any other reason(s) that wasn't apparent to me.

The problem now for me is finding a single rail power supply that can support my developing AMD 3500+ Winchester computer in a full tower ATX case with a Gigabyte SLI motherboard, dual 6800 GT's and 4 SATA drives. Do I chose the Enermax 600W SLI or some single-rail power supply?

First of all, the Enermax 600W SLI is a 2 rail PSU if you assumed otherwise & whatever floats your boat. As long as you're aware of the pros & cons of both single & 2+ rail PSUs as well as other features (or lackof), not just the # of rails.

And what are your thoughts on the Thermaltake Silent PurePower ATX 12V 2.0 Plus EPS 680W tri-rail?

No important thoughts. Just questions if I were shopping. Like which 12V rail powers what components, the price, reliability, features, limitations if any, etc.