20pin power connector

[dtranftw]

Hi i am thinking of building a spare pc for my brother and i was wondering if a 20 pin motherboard cable will work on a 24pin motherboard.

My parts for the build are : AMD Athlon x4 760k, 4gb of ram , 500 gb hdd, an old ati 2400xt and a psu 400w atx

 

[nukemaster]

Check the manual to be sure, but many boards will work without the extra 4 pins.

 

[dtranftw]

Check the manual to be sure, but many boards will work without the extra 4 pins.

it was an oem machine so i am not sure

 

[nukemaster]

Well I guess you can try it. I do not think it will cause any issues(make sure you connect the 4 or 8 pin cpu power cable as well).

 

[InvalidError]

The 24 pins connector is a hold-over from the days before ATX12V and PCIe where the CPU and everything else on the motherboard was powered through the 20 pins ATX connector. The total current was pushing the limits on 3.3/5/12V and one extra pin for each were added to bring the average current per pin back down.

Now that nearly everything is powered by the 12V rail alone and that the major loads have their own dedicated 12V feeds, the 24-pins ATX connector is superfluous and serve little purpose beyond maintaining compatibility with PSUs that have 24 pins connectors. Most motherboards should not care whether those extra pins are there or not - they are all soldered to the same copper trace/pour/plane and that's it.

 

[Calvin7]

The changeover from 20 to 24 pins was to power the PCIe x16 slot. No power would go to that slot if the extra 4 pins were omitted.

 

[nukemaster]

The 24 pins connector is a hold-over from the days before ATX12V and PCIe where the CPU and everything else on the motherboard was powered through the 20 pins ATX connector. The total current was pushing the limits on 3.3/5/12V and one extra pin for each were added to bring the average current per pin back down.

Now that nearly everything is powered by the 12V rail alone and that the major loads have their own dedicated 12V feeds, the 24-pins ATX connector is superfluous and serve little purpose beyond maintaining compatibility with PSUs that have 24 pins connectors. Most motherboards should not care whether those extra pins are there or not - they are all soldered to the same copper trace/pour/plane and that's it.

Straight 12 volt boards would be great. Only a few OEM's do this.
We still need 5v for some devices(usb/ssd/parts of the hard drive/ect). It sure could simplify things.

The changeover from 20 to 24 pins was to power the PCIe x16 slot. No power would go to that slot if the extra 4 pins were omitted.

I have run many first generation boards without this issue. I wonder how many boards this effected. PCI-e does not even have 5 volts as far as I know and one of those extra 4 was 5 volts.

 

[dtranftw]

well i was planning to put a gts 250 in the x16 slot since the psu has a 6pin lead.
I checked on a wattage calculator and it said with the gts 250 i only need atleast 300 watts of the 400 i have

 

[nukemaster]

A GTS 250 should hang out in the 150 watt peak area since a pci-e slot is rated for 75 watts and the 6 pin cable is rated for the same.

Please check the power supply label to see how may amps or watts it has at 12 volts since that is the rail that is most used.

 

[dtranftw]

The psu is oem psu from gateway
its a Bestec ATX 400w-GW 12V/ 18A with a 24pin power connecter (i just found that out lol)

 

[nukemaster]

18 amps @ 12 volts(216 watts) is very low for a 400 watt power supply.

Is it a multi-rail unit by any chance? If it is it should list a combined output.

 

[dtranftw]

I am not sure i will take a pic of the psu when i have the time

 

[dtranftw]

+12V1 /18A +12Vcpu/ 16A
+5V / 18A -12V / 0.3A
+3.3V / 25A +5VSB / 2A

Im not sure if that would help you but thats what i read on the psu

 

[nukemaster]

I am going to have to guess the second "cpu" rail has something else on it.

Does it list a combined for those 2 rails by any chance.

 

[dtranftw]

so when you mean combined like combined as 12V and another 12V next to it.
Because it only has one 12V and 12Vcpu

 

[nukemaster]

It is normally listed as 12v + 12vcpu must not exceed XXX watts or XX amps. They all show it a bit differently.

The reason it is important is your 400 watt power supply can not output 408watts(that would be if the rails added together. This rarely happens and as you can see it is more than the power supply is rated for)

Here is a multirail example image.

It would seem to have 30 amps(360 watts would be impressive from a 300 watt power supply) if you added the 2 12 volt rails.
It has 22amps(264 watts) combined. So as long as the 2 rails to not pass the set limits and the combined do not pass 264 watts, everything is good.

 

[dtranftw]

how can i send a picture on toms hardware

 

[InvalidError]

how can i send a picture on toms hardware

You can't.

You have to put the picture elsewhere and use an embed link in your post.

 

[dtranftw]

oh alright

 

[dtranftw]

Its a 5V & 3.3V 130 W Max
and only a 12V1 & 12V cpu+ 30A Max
so im guessing no multi rail psu

 

[nukemaster]

You have 30 amps or 360 watts @ 12 volts.

That should be enough as long as it delivers its rated power.

Lower powered video cards like the 750 and 750ti are better options because they are more easy on the power supply if you can get one(and should be faster too).

 

[dtranftw]

i was thinking about that because i already have one in my main build right now. And 30 amps max

 

[dtranftw]

I assume that this is a single rail can it still handle a gts 250 and a athlon 760k. The psu has a 6 pin pci

 

[nukemaster]

It should. It may be a bit hard on it, but the system should not need more than the power supply label lists(remember older power supplies start to loose some capacity so I would keep an eye on it.).

It is actually multi rail, but that is not an issue as such.

Lower powered cards may be a better long term bet(even a 5770 should take less and be faster), but for a second hand system, you work with what you have.

 

[dtranftw]

Ok thank you sir.