Very Ambitious Pico/Phantom Proposition

El Doug · Post by **El Doug** » Mon Jul 03, 2006 12:36 am

Running an X2 4400+ and 7800gtx on a phantom, Ive been very pleased the last 6 months. However Ive been itching to try SLI ever since the next gen cards have been released, and the prices have gone down. All cooling aside (ill handle that myself)...

I have done the wattage calculations based on the graphic card usages from the published material, and believe I could run two on the phantom. I could then get the 4400+ (which is at 1.175v @ 8x250=2ghz) on a picoPSU 120watt, which I know (this time with kill-a-watt experimentation) is higher than my dual-CPUBurn load of 112watt (this with a TNT PCI card for video, to eliminate the video power drain from the calculation).

My question is, how viable is it to run both video cards off of a phantom? Though the dual 12v rails on paper have enough amperage, I am aware that the 12v1 is only utilized in conjunction with the the 5v and that the total 12v amperage listed cannot be used at once, as it exceeds 350 watts. Assuming that at load 2 7800gtx's suck up 180 watts (this is a very liberal estimate - it will almost assuredly be less, as the most ive seen drawn is 80watt on a single card), will the PSU stand up to that, if all the power comes in 12v form?

edit: i just reread this and am aware that it is very unclear

Im happy to entertain questions about my idea - please dont abandon me based on the poorly delivered post

nemo · Post by **nemo** » Mon Jul 03, 2006 1:33 am

so you are planning to use the phantom and a pico at the same time, both powering one computer?

cool

nici · Post by **nici** » Mon Jul 03, 2006 2:09 am

I guess he is, shouldnÂ´t be a problem really.. ThereÂ´s adapters available to connect two PSUs to the mobo. One 24pin goes to the mobo as usual, and the green wire goes to the other PSUs connector to start it.

Do modern CPUs draw all their power from the 4-pin connector? Cause if they do you could connect the phantom to the mobo and just a 4-pin from the pico.

Im not convinced this is neccesary though. But what do i know...

jaganath · Post by **jaganath** » Mon Jul 03, 2006 4:22 am

My question is, how viable is it to run both video cards off of a phantom? Though the dual 12v rails on paper have enough amperage, I am aware that the 12v1 is only utilized in conjunction with the the 5v and that the total 12v amperage listed cannot be used at once, as it exceeds 350 watts

Will this be a Phantom 350 or 500? Beware, another user has reported cold boot problems with a Phantom 500 and a P4 630 paired with a X1900XTX, which according to the rated amperage shouldn't be a problem, but it is.

El Doug · Post by **El Doug** » Mon Jul 03, 2006 10:10 am

yes, id be using both PSUs at once. no, they would not be connected.

its a phantom 350, and i want it to ONLY power the GPUs and drives. I know that the picoPSU would be able to handle the cpu/mobo (and there are no peripheral cards less the single graphics currently in there). The question is, can the phantom handle the load of 2 7800gtx, so long as it is NOT connected to a cpu/mobo?

I have already figured out how to rig up a second power button for each PSU, so that should not be a problem

the entire setup works on paper, i suppose my only question is if the Phantom350 can handle 2 7800gtx, with nothing else attached

SebRad · Post by **SebRad** » Mon Jul 03, 2006 1:47 pm

Hi El Doug, is there any reason to suppose the Phantom couldn't handle SLI 7800GTXs. It's lesser 12V rail is spec'd at 16A, that's 192w, which is more than you say is plenty for them. Assuming you can get it to work as a secondary PSU I see no problem at all with the setup.
The 112w you mention for the CPU is presumably for the whole system(less the 7800), is that a "from the wall" figure or have you adjusted it for PSU efficiency as a "DC load on the PSU" figure?
The numbers suggest you could possible run the whole system and SLI 7800GTXs off the Phantom alone! Not sure I'd be happy to run a fanless PSU at 90% load with out at least a very quiet fan blowing on it, although the SPCR review says at that load it would only be generating 35-40w of heat of it's own.
You could always try and see, worst case the Phantom can't handle it / over-heats and shuts down.
Seb

El Doug · Post by **El Doug** » Mon Jul 03, 2006 5:10 pm

interesting idea. perhaps I WILL try running the SLI off of the phantom alone, before bothering with a complicated dual-independant-power setup

i guess i knew it was possible, i was just scared to put that much load on it.

good deal! Ill be trying this out then

the 112 IS from the wall, so it looks like the system drinks even less! u just gave me a great boost of confidence

btw - i do have 2 L1A's @ 5v for some system flow (and there are some holes near PSU front, to allow some flow around it - the case is an x11). the fans also cool off the heatsink at the end of the heatpipe on the A8N-premium

ultraboy · Post by **ultraboy** » Mon Jul 03, 2006 5:59 pm

El Doug wrote:...its a phantom 350, and i want it to ONLY power the GPUs and drives....

I have a dual PSU set up, and am recalling my reading on the subject a while back - there're a few caution about powering VGA card that requires additional power through molex plug - it's recommended that the molex plug came from same PSU as MB plug. This is to avoid 'cross talk' of power

, and something to do with power regulator of PSU (more understandable).

Being a total noob on this, I have the slave PSU supply power only to drives and fans.

May be other knowledgable members can confirm/deny this.

Cheers.

Edit: Just see that El Doug has decided to go with one PSU now. So this post is less relevant (for now).

El Doug · Post by **El Doug** » Mon Jul 03, 2006 7:06 pm

ultraboy wrote: Edit: Just see that El Doug has decided to go with one PSU now. So this post is less relevant (for now).

FOR NOW is the key phrase. Ill soon find out how viable this is... give me a few days

ultraboy wrote:I'm having a dual PSU set up, and am recalling my reading on the subject a while back - there're a few caution about powering VGA card that requires additional power through molex plug - it's recommended that the molex plug came from same PSU as MB plug. This is to avoid 'cross talk' of power , and something to do with power regulator of PSU (more understandable).

Being a total noob on this, I have the slave PSU supply power only to drives and fans.

May be other knowledgable members can confirm/deny this.

Id certainly love to hear more about this - can anyone expand?

nici · Post by **nici** » Mon Jul 03, 2006 10:09 pm

What i meant with the adapter was that only one PSU is connected to the mobo, but the start-up wire goes to both of the PSUs.. Check the SPCR silverstone TJ07 review if thereÂ´s a picture of the adapter. No need for two power buttons if you do end up using two PSUs..

El Doug · Post by **El Doug** » Fri Jul 07, 2006 7:32 pm

well fellas, i thought id give a follow up

in effect, i just want to praise the phantom 350 even MORE! its the most amazing PSU in existence. I am now running 7800gtxSLI - survives all stress tests. It's simply incredible the kind of output this thing really has!

Not to mention that having the second card with an AC Silencer has helped system tems even more - of course having the first card on reserator wasnt helping that much

all in all, "wow" is the only word that comes to mind.

autoboy · Post by **autoboy** » Fri Jul 07, 2006 8:07 pm

I'm not that suprised because the phantom 500 is just a 350 with a auxilary fan. The 350 is capable of more output than they rate it for and if you have good airflow through the 350 it should provide enough power for any system.