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using external power supply for graphics card

Geofrancis said:
the 4850 is going into the computer im just trying to figure out how to do it.

i already sold the 4850 and wanted to buy a hd 4670 but it got returned so now i have the challenge of fitting it into the case and powering it.

so stop telling me to get a new card or case or power supply or that it cant be done.

it can be done i just done know how yet lol


the pci-e riser ribbon cable has already been ordered and i have the 120w psu already waiting so its just a matter of time
Click to expand...

My bad for trying to give you another suggestion :/. I know i would acctualy try doing it to :toast:. I did use 2 dif power supplys 1 time. I hooked up my 530 watt to the 260 and the res of the rig, then i ghosted the power supply with a paper clip bent to the ground, to one of the green cables and what it did was just turn on automaticly. So just ghost the power supply first, it was a danger to me because i didnt know if my 8800gt was going to blow up(it was being power by the power supply that i paper cliped). But i shuved the AC plug into the moded power supply and pushed the switch on the rig were everything was at the same time, and tada is worked just fine for some tripple 19 inch screen madniss in crysis. Played everything on high exept LOD was on low, which helped alot at about 20+Fps most the time, great having such a rape FOV in crysis. I could see the rocks behind me :roll:

From my single experience with a simple mod it will be fine XD. :cool:
 
3volvedcombat said:
My bad for trying to give you another suggestion :/. I know i would acctualy try doing it to :toast:. I did use 2 dif power supplys 1 time. I hooked up my 530 watt to the 260 and the res of the rig, then i ghosted the power supply with a paper clip bent to the ground, to one of the green cables and what it did was just turn on automaticly. So just ghost the power supply first, it was a danger to me because i didnt know if my 8800gt was going to blow up(it was being power by the power supply that i paper cliped). But i shuved the AC plug into the moded power supply and pushed the switch on the rig were everything was at the same time, and tada is worked just fine for some tripple 19 inch screen madniss in crysis. Played everything on high exept LOD was on low, which helped alot at about 20+Fps most the time, great having such a rape FOV in crysis. I could see the rocks behind me :roll:

From my single experience with a simple mod it will be fine XD. :cool:
Click to expand...

its good to see that somone has already done the same mod and survived without being left with a chard mess
 
I recently tried out a multi PSU configuration with my RIG.

Used dedicated Corsair VX450W for my HD4770s.

Used dedicated Corsair TX650W for CPU, MB, hdds, fans.

I did this by connecting the VX450 to a separate MB without a CPU. I would first power up my MB powered by the VX450W feeding the HD5770s.
Then I would immediatly power up my CPU MB powered by the TX650W powering CPU and other related hardware listed above.

Ran OCCT PSU test and discovered my power ripples were less which is better. Not by much though.
Only performance gains I noticed were with the improved ripple. RIG can still OC just as good. OCCT PSU analysis is questionable.

So in short IMO it's best to get a decent single PSU that can power every thing right. Less hassels with wiring and potential extra heat from wires in case.
 
As sneekypeet said - it's the amperage that matters the most. Could you get any specifications of this 120W PSU? How much from the total output power is purposed for 12V with what amperage?
 
im going to assume it will do 8 - 10 amps, 120watts devided by 12v = 10.

he said it only supplys 12 volts.
 
Oh, my bad, sorry. So IMO with a safe way to power on and off both PSUs it should be okay.
 
like i said before i still have a pico psu from a previous project and i was thinking of using the psu-on pin and a ground pin on the pico psu connected to the motherboard power supply socket so that they both get the power-on signal together and power on instead of using a separate motherboard.

and a 120w / 12v = 10A like slyfox2151 said.

i also have a digital multimeter to verify voltages so i will try to get readings of both powers supplys to verify the voltages.
 
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your math for the 120W is overrated...you are doing your math based on a 100% efficient PSU. More realistically you are getting 6-8 amps durring opperation. I would still be concerned that it isnt enough power, then you risk burning the spare PSU and possibly the card itself.
 
I do not believe 10 amps will be enough at all :)
 
If the other PSU is sepperate, why not use a decent one?

Or one with long wires ? heh

get rid of the built in one and just feed the wires through, have the other PSU sitting underneath hidden or something
 
Like others already said "in a perfect world" the PS may put out that much power (but its more likeli not able to.

So it may work but would be forcing the Pico PS to its limit (and its life may be cut really short). I use on in my Lego comp (150 watt version). I really like it and its very efficient (over 90%) But I wouldnt think to power a 4850 with it.

Now all that said My personal comp (W3503, X58mobo,3 Hdds, two 4770s and asus sound card is pulling 158 watts at the plug right now while I am typing this) So it "MAY" work but I would definitely pick up a "Kill A Watt" first than measure the power needed exactly (rather than guessing)

Here is a better idea
http://www.overclockersclub.com/reviews/epower_2kw/

just a bit of Overkill... You are probably better off trying to fit a bit better PS to replace the 200 watt one rather than messing with all the wiring.
 
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Geofrancis said:
like i said i want to run a external 12v power supply into the pci-e power socket on the graphics card to take the load off the internal power supply.

i know there is graphics card power supplys out there but i already have this 120w psu here so i want to use it.
Click to expand...

my freind wanted to do the samething. and he did.....just after about 2 week his card died, he sent it back, and they said they do not cover warranty of volt/power damaged card

so 2 things learnt from that.
1, it will ruin your card. and,
2, it will ruin the warranty even if your card barely survives
 
i found a site with the power consumption figures for an hd4850.
http://translate.google.com/transla...phics/index30.php&sl=de&tl=en&history_state0=


PEG 3,3V 0.75 A 3.30V 2.5 W
PEG 12V 4.38 A 11.89 V 52.1 W
PCIe 6-Pin 7.82 A 11.97 V 93.6 W

Total 148.2 W

so 7.28A should be fine on the 120w psu but i will be undervolting it so it should be 10-20w less

50w is still alot on the 200w internal psu r but thats what a hd4650 would have used.


i thought the way efficiency worked was that if you were drawing 100w of power from a 80% efficient power supply you would have to draw an extra 20w or 120w total from the ac source. if it was 100% efficient it would draw only the 100w from the source


lol warrenties i dont think i have ever used one in 9 years just look at what happened to a brand new eeepc :)
eeepc link in my sig.
 
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You mean like this? That -was- Vector 120 to 12v adaptor for using automotive type 12v coolers in the house. Powering a HD3870.

attachment.php
 
The hardware side can be done as I have hardwired a spare single rail 600W PSU I have(there are plenty of guides on the webz on how to hard wire the 20/24 pin Atx plug) to run one of two GTX275's I had as I thought that with an i7 overclocked my 750W may have been a little "close to the wire"...... it worked like a charm.

My concerns are similar to others though, that again you will be running close to the wire with your 2nd unit, IMO you need a healthy margin. If your concerned about cost, for the sake of that old smell of burning and the price of shipping only....you can have my spare 600W 30A single rail unit (Sansun Black..... nothing special) ..... then you can get rid of both of those hideous units!
 
i am keeping the case and the power supply that's in it i am not getting a new one.

if the 120w dc brick is not powerful enough i seen 200w dc power supply's on ebay that do 12v but im not sure how to power it up with the main power supply without the pico psu. if someone could show me a circuit with a relay that would turn the power on on the second power supply when the main one comes on it would be helpful.
 
coming up...

Do you want to leave the bricks ac on and switch the 12v side? Or do you want to switch the 120v side? They don't draw very much without a load so don't worry about power consumption.
 
idealy i would like the relay on the 12v side. i dont like the idea if mains power cables inside my computer.
 
Guys PLEASE STOP trying to talk him out of this. I really want before and after pictures.
 
Geofrancis said:
idealy i would like the relay on the 12v side. i dont like the idea if mains power cables inside my computer.
Click to expand...

You got it. I'll post it in schematic format so it can get stickied once and for all. ;)

I have to run out for a few, ironically to pick up a power supply, and when I get back I'll post it up.

All you do is pick up a 12v (or 5v) relay and connect the coil to a 12v (or 5v) supply from your main PSU. That will be one black for ground and one yellow for +12v (or red for 5v). This activates the relay's coil when you turn on the computer. On the 12v adaptor your using for the GPU, cut the positive and put those wires across the normally open switch contacts of the relay. They might be labled 'no' (normally open) and 'com' (common) in a typical spdt (single pole double throw) relay.
They would look like this on the relay's schematic drawing.

--------
------^ Notice the contacts don't touch. This is the resting position (normally open).

Usually a diode is placed in reverse across the relay's coil to catch emf spikes from the coil. You don't have to worry about that so much because the main psu's caps and filtering can absorb it. If you do want that protection, place a diode across the relay's coil like this (+) -----|<----- (-) to catch the emf spike. The coil has no polarity so the + and - would be determined by which way you soldered the main psu's power to the relay's coil. Diode stripe (cathode) to the positive side.
 
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Lazzer408 said:
You got it. I'll post it in schematic format so it can get stickied once and for all. ;)

I have to run out for a few, ironically to pick up a power supply, and when I get back I'll post it up.

All you do is pick up a 12v (or 5v) relay and connect the coil to a 12v (or 5v) supply from your main PSU. That will be one black for ground and one yellow for +12v (or red for 5v). This activates the relay's coil when you turn on the computer. On the 12v adaptor your using for the GPU, cut the positive and put those wires across the normally open switch contacts of the relay. They might be labled 'no' (normally open) and 'com' (common) in a typical spdt (single pole double throw) relay.
They would look like this on the relay's schematic drawing.

--------
------^ Notice the contacts don't touch. This is the resting position (normally open).

Usually a diode is placed in reverse across the relay's coil to catch emf spikes from the coil. You don't have to worry about that so much because the main psu's caps and filtering can absorb it. If you do want that protection, place a diode across the relay's coil like this (+) -----|<----- (-) to catch the emf spike. The coil has no polarity so the + and - would be determined by which way you soldered the main psu's power to the relay's coil. Diode stripe (cathode) to the positive side.
Click to expand...


i thought thats how to do it but i wanted a second opinion before i cut into anything.
 
hmmmn if it was me id just get a better cleaner psu, its not ideal to run 2 psus

if you can afford a psu just for the gpu (not that in this case as its just a spare you had lying around) you can more than likely afford a single good amperage psu

i think it would run okay but the amperage might be a little low
 
Or pay me £20+P+P for this dedicated 25A 250w GPU PSU I have here, and all your worries will be over.
 
Never mind all this PSU talk, your morex case is WAY TOO SMALL to handle the thermal exit requirements for a 4850, esp. with that RAID rack.

You have a fabulous rig there... dont spoil it trying to get a hot number in a tight space ;)
 
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