Power Supply A Guide to 12V PSU

Valantar

SFF Guru
Jan 20, 2018
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That one is missing 4pin eps. Most motherboards need both 24pin and 4pin atx. That one is just 20+4.
Ah didn't realize it was only a 20pin ATX connector. Guess he would need to step up to the 150XT or J-Hack as @Choidebu mentioned
Are you sure it's an expansion to 24-pin ATX power and not a 4-pin EPS? I'm running a cheap Aliexpress knock-off of one of these in a low-powered build I have, and it has a 20-pin + a 4-pin EPS (and works just fine, despite the ATX connector on the motherboard being 24-pin).

Also, there's this accessory:
http://www.mini-box.com/4-Pin-P4-Power-Cable_2
 

Valantar

SFF Guru
Jan 20, 2018
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I'm surprised. But it makes sense. The additional 4pin atx on the motherboard is for pcie.
Hm. The motherboard in my build actually has a PCI slot (even for a low-end integrated Celeron/Pentium (atom-based) ITX board I was surprised at that - it's not that old), so I suppose that might explain why it would work? Then again, do most motherboards have more than one power plane per voltage, and as such any knowledge whatsoever if the last four pins are actually connected?

Edit: from looking at the wiring of the PicoPSU, it has to be an EPS connector - it only has 12V and ground. Forcing that into the last four pins of your 24-pin would be ... bad.
 

Thehack

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Hm. The motherboard in my build actually has a PCI slot (even for a low-end integrated Celeron/Pentium (atom-based) ITX board I was surprised at that - it's not that old), so I suppose that might explain why it would work? Then again, do most motherboards have more than one power plane per voltage, and as such any knowledge whatsoever if the last four pins are actually connected?

Edit: from looking at the wiring of the PicoPSU, it has to be an EPS connector - it only has 12V and ground. Forcing that into the last four pins of your 24-pin would be ... bad.
The power plane may be the same, I think, but a motherboard will not boot without eps plugged in. I do not know about the additional 4pin on the atx and how that plays out.
 

Soul_Est

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Feb 12, 2016
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I'm having a bit of trouble understanding exactly how much power to spec for the PDCB considering that it may not do much more than powering the motherboard, PCIe, and M.2 drives for my build. I have a 250W RGeek unit (not the best, I know) at the moment and looking at either the EPP-400-12 or EPP-500-12 to power my Ryzen 7 2700X and Radeon RX Vega 56. I will be undervolting and power capping both of those parts to improve efficiency.

For those who are looking to get the EPP-500-12, Arrow Electronics does have a listing for it and is showing a lead time of 11 weeks as of this post.
 
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smitty2k1

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Dec 3, 2016
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I'm having a bit of trouble understanding exactly how much power to spec for the PDCB considering that it may not do much more than powering the motherboard, PCIe, and M.2 drives for my build. I have a 250W RGeek unit (not the best, I know) at the moment and looking at the either the EPP-400-12 or EPP-500-12 to power my Ryzen 7 2700X and Radeon RX Vega 56. I will be undervolting and power capping both of those parts to improve efficiency.

For those who are looking to get the EPP-500-12, Arrow Electronics does have a listing for it and is showing a lead time of 11 weeks as of this post.
Just because of the Vega 56 I'd say go with the 500w unit, even though there is a lead time.
I've had nothing but issues powering my Vega 56. The OCP was tripping on my Silverstone ST45 gold (450w) and then later on my Silverstone SX650 and then later on my Corsair SF600 platinum. The ST45 gold ran my GTX 780 superclock for years without issue but the Vega immediately brought it to its knees. It seems something with Vega can cause very short duration spikes. The only thing to prevent the trips was to put the Vega in power saver mode. Silverstone acknowledged the issue and made some sort of engineering change and RMA'd my unit. Corsair wouldn't acknowledge the issue but mentioned I had a very early production unit and begrudgingly RMAd it with a new one (that so far seems to be doing alright...)
 
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Thehack

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I'm having a bit of trouble understanding exactly how much power to spec for the PDCB considering that it may not do much more than powering the motherboard, PCIe, and M.2 drives for my build. I have a 250W RGeek unit (not the best, I know) at the moment and looking at the either the EPP-400-12 or EPP-500-12 to power my Ryzen 7 2700X and Radeon RX Vega 56. I will be undervolting and power capping both of those parts to improve efficiency.

For those who are looking to get the EPP-500-12, Arrow Electronics does have a listing for it and is showing a lead time of 11 weeks as of this post.
A lot of the cheaper options have a high rating but they use the number from 3.3 and 5v to make it look high. The Rgeek is likely 120w on the 12v rail.
 

Soul_Est

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Thank you both for your feedback.

Just because of the Vega 56 I'd say go with the 500w unit, even though there is a lead time.
I've had nothing but issues powering my Vega 56. The OCP was tripping on my Silverstone ST45 gold (450w) and then later on my Silverstone SX650 and then later on my Corsair SF600 platinum. The ST45 gold ran my GTX 780 superclock for years without issue but the Vega immediately brought it to its knees. It seems something with Vega can cause very short duration spikes. The only thing to prevent the trips was to put the Vega in power saver mode. Silverstone acknowledged the issue and made some sort of engineering change and RMA'd my unit. Corsair wouldn't acknowledge the issue but mentioned I had a very early production unit and begrudgingly RMAd it with a new one (that so far seems to be doing alright...)
Duly noted. I can only get a quote on the EPP-500-12 at the moment so I'll wait on that for now. Interesting to note the Vega 56 pulling that much. Which card was it? I have a Red Dragon.

A lot of the cheaper options have a high rating but they use the number from 3.3 and 5v to make it look high. The Rgeek is likely 120w on the 12v rail.
Ah I see. After looking over the power draw for the motherboard, memory, and storage, I should be good there. Looking at the tools and supplies that I need as well as a way of powering the build in the interim.
 

Soul_Est

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Meanwell sent me the test report of the EPP-500-12.

Ripple is pretty high at 187 mVp-p.
Yikes. Will need a filter circuit.
Dang. I'll probably be biting the bullet for this and the other parts that I need in June to continue work on Full Circle. Would you mind posting that report to the Resources area, please (if you're allowed to) @aquelito ?
 

proton007

Cable Smoosher
Aug 8, 2019
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Hello there!
fellow newbie here, I followed the guide and am building my own SFF. Would appreciate if someone with more experience could clarify the 4/8 pin ATX confusion.

Here's the component list:

CPU: Ryzen 5 3400G
Motherboard: Asus ROG Strix B450 I
SSD: WD Black
Cooler: Noctua L9x65
Case: Lazer 3D HT5 Stealth
PSU: Meanwell EPP 300-12 + PicoPSU 160W
Case Fans: 2x Noctua 80mm fans

I noticed that the Pico PSU has a 4 Pin ATX CPU connector, but the mainboard has an 8 pin ATX socket.

Link to motherboard manual: https://dlcdnets.asus.com/pub/ASUS/...G/E14337_ROG_STRIX_B450-I_GAMING_UM_PRINT.pdf

This is what the motherboard manual states: "Do not forget to connect the 8-pin EATX12 V power plug. Otherwise, the system will not boot !"

On page 2-8 however, the pictures show that it is possible to connect a 4 pin, with the following text: "Ensure to connect the 8-pin power plug ".

What is this supposed to mean? Does it mean that the motherboard won't POST with a 4 pin connector, or is this merely implying not to forget plugging in the ATX connector? Alternatively, do I need a 4 to 8 pin adapter?
 

Thehack

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Hello there!
fellow newbie here, I followed the guide and am building my own SFF. Would appreciate if someone with more experience could clarify the 4/8 pin ATX confusion.

Here's the component list:

CPU: Ryzen 5 3400G
Motherboard: Asus ROG Strix B450 I
SSD: WD Black
Cooler: Noctua L9x65
Case: Lazer 3D HT5 Stealth
PSU: Meanwell EPP 300-12 + PicoPSU 160W
Case Fans: 2x Noctua 80mm fans

I noticed that the Pico PSU has a 4 Pin ATX CPU connector, but the mainboard has an 8 pin ATX socket.

Link to motherboard manual: https://dlcdnets.asus.com/pub/ASUS/...G/E14337_ROG_STRIX_B450-I_GAMING_UM_PRINT.pdf

This is what the motherboard manual states: "Do not forget to connect the 8-pin EATX12 V power plug. Otherwise, the system will not boot !"

On page 2-8 however, the pictures show that it is possible to connect a 4 pin, with the following text: "Ensure to connect the 8-pin power plug ".

What is this supposed to mean? Does it mean that the motherboard won't POST with a 4 pin connector, or is this merely implying not to forget plugging in the ATX connector? Alternatively, do I need a 4 to 8 pin adapter?
Your acdc power supply is a bit over kill.

You do not need all 8 pins. 4 will work just fine.
 

Thehack

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