Why can't my GPU work when it only require 18.5A and my PSU has 17A?
- Thread starter GTHell
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k1114
Titan
- May 2, 2010
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This isn't a simple light bulb that just dims with less less power. If a computing device get's less power, the transistors don't get a 1 or 0 like it's supposed to so throws an error. That's not even a simple error, that a major catastrophic error causing a crash. There's a reason there is further vrm and extra power management on hardware. Not to mention the gpu isn't the only component using the 12v rail. Also you don't want to go much more than 75% of the psu or overwork it and die faster.
burgessanthony
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- Jun 27, 2012
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You need a new psu of at least 450w and a quality unit. But post your specs so we can advise. Trying to run a 225w gpu on a 200w psu will never work
Shaun o
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- Oct 7, 2007
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I`m afraid you are totally miscalculating the amps
You are forgetting that the 12v power supply to the motherboard also, the 24 pin ATX power block requires amps as well.
And also the E-ATX or 12v eight Pin requires amps as well.
Add in each hard drive, or optical drive in the system on average that uses 1 to 2 amps of power each.
Even if your graphics card on it`s own required a total of 18.5w from the 12v power rail of any PSU.
How many amps you have left the 12v power rail can provide will be around 9 to 10 amps.
Every device such as a hard drive, or an optical drive will draw a set amount of amps from the 12v power rail of the psu.
Once you have worked out what all the other components or parts of the system draw or require you can calculate how much is left for the graphics card.
The 17amp rating for the 12v power rail is for everything that requires 12v of power of the system.
Your looking at a power supply that can provide about 40 to 42 amps total to get a 225w card at 18.5 Amps along with the rest of the ampage needed for other components of your system running with 12v power feeds and a amp draw.
You are forgetting that the 12v power supply to the motherboard also, the 24 pin ATX power block requires amps as well.
And also the E-ATX or 12v eight Pin requires amps as well.
Add in each hard drive, or optical drive in the system on average that uses 1 to 2 amps of power each.
Even if your graphics card on it`s own required a total of 18.5w from the 12v power rail of any PSU.
How many amps you have left the 12v power rail can provide will be around 9 to 10 amps.
Every device such as a hard drive, or an optical drive will draw a set amount of amps from the 12v power rail of the psu.
Once you have worked out what all the other components or parts of the system draw or require you can calculate how much is left for the graphics card.
The 17amp rating for the 12v power rail is for everything that requires 12v of power of the system.
Your looking at a power supply that can provide about 40 to 42 amps total to get a 225w card at 18.5 Amps along with the rest of the ampage needed for other components of your system running with 12v power feeds and a amp draw.
burgessanthony
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Well as someone said, transistors aren't like light bulbs, nor are PC components. They need sufficient power to operate full stop.
I'd be careful of that 700W then....40x12 is only 480W which implies it is LIKELY a very poor quality unit. A good 700W unit will have around 55A on the 12V rail. Just FYI
I'd be careful of that 700W then....40x12 is only 480W which implies it is LIKELY a very poor quality unit. A good 700W unit will have around 55A on the 12V rail. Just FYI
burgessanthony
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Is it? I couldn't find a single gts250 that's rated at 225. That looks like it's supplied power from the mobo and pcie which is much different to what it will draw.
k1114
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Just because the pcie slot and 6 pin can deliver that max amount, doesn't mean the card will draw that much. It will only use as much as it needs and it's only a 150w card. Most cards are oc so slightly above 150w, so 75w from slot and 75w from 1 6 pin is not enough. That's why your card has an extra but it's only slightly above 150w plus extra room to oc yourself as many manufacturers do as well.
It use for SLI and OC that why is has 2x power connector. This card is too old but it don't bother me much since it can run CSGO at 75 at 1080p. Pretty good for 30$ except directX 11 not support.
This card won't boot with CMOS plug in at all. Do you know why? Before this post I thought that it's a PSU problem so I go get 2 new PSU just to realize that it has nothing to do with PSU. I need to remove CMOS or the Card to get computer boot up. The old card work just fine. I don't have sound with CMOS out.
This card won't boot with CMOS plug in at all. Do you know why? Before this post I thought that it's a PSU problem so I go get 2 new PSU just to realize that it has nothing to do with PSU. I need to remove CMOS or the Card to get computer boot up. The old card work just fine. I don't have sound with CMOS out.
Mark RM
Admirable
- Jul 16, 2014
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Actually, while that's the specification, a 6 pin PCIe cable could be more than capable of putting out double that - If weren't for trying to keep things compatible with crappy multi rail PSU's there's literally no reason you could not draw a couple hundred watts over a six pin cable of adequate gauge. In fact we've done this many times cooling frankenstein builds with cascades.
When you see two six pin PCie connectors on a low end card like a 250, you know it's because THEY know that half those purchases are going to be hooked to Yo Mamma's brand PSU with four 12v rails, each of which is not actually capable of delivering the wattage claimed in the label.
Basically 1 six pin cable could be plenty, limitations to prevent out of spec draw from a power source (SLOT or cable type) are firmware driven artificial limitations like a speed governor on a car.With the 480 AMD calibrated their governors wrong and overrode the BIOS settings in the driver (for example).
Here's a good explanation on this with an RX 480 that was recently linked here in the forums, watch what they had to do to get it up to 1500MHz with the single six pin.
https://www.youtube.com/watch?v=Jq47qmwcus8
You're right about everything else of course.
Mark RM
Admirable
- Jul 16, 2014
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Right... those standards are designed to be exceeded and if they weren't every serious OC would fail. The standard is 75 w, and the speed limit is 100kph. No one sticks to either.
Adding two ground cables to a six pin cable and making it an eight rated at 150W doesn't make it capable of magically delivering more wattage , It just offers a way to potentially alleviate pain on the voltage regulator by lowering ground resistance. The ability to deliver the amps used in an 6 or 8 pin configs was always there in better PSU's, the 75W limitation is as artificial as my Granny's teeth.
Adding two ground cables to a six pin cable and making it an eight rated at 150W doesn't make it capable of magically delivering more wattage , It just offers a way to potentially alleviate pain on the voltage regulator by lowering ground resistance. The ability to deliver the amps used in an 6 or 8 pin configs was always there in better PSU's, the 75W limitation is as artificial as my Granny's teeth.
- Nov 19, 2010
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Really, at this point, what would make sense is finding the specific GPU you have so that people can look at the actual specs rather than your reporting of what the specs are.
k1114
Titan
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Sli does not require an extra power cable. There is no such thing as a 225w 250. Not even oc gets that high. You're going to have to oc a 275 just to get to that power and you can read in depth reviews and articles on ocing 200 series and see their power consumption. A 250 does not oc a lot and you will hardly go above 170w oc. You have to ask about amps so it's understandable you don't know about other aspects of the pc world. But it's hard to help if you refuse to accept help.
- Nov 19, 2010
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