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Question on 12v power connections B550 Pro4

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    Posted: 21 Jun 2023 at 9:03pm
ASRock B550 Pro4: https://www.asrock.com/mb/AMD/B550%20Pro4/index.asp

This board has an 8-pin right next to a 4-pin 12v power connection. The manual states:

"This motherboard provides a 8-pin ATX 12V power connector. To use a
4-pin ATX power supply, please plug it along Pin 1 and Pin 5" (IE: 4 of the 8 would be vacant?).

I have both 4 and 8 pin connectors on my PSU. Is it intended that:

1. I plug in one 8-pin and leave the 4-pin unplugged.
2. I plug in a 4 (2x) pin into each (compatibility assuming my PSU only had 4 pins?).
3. Plug in an 8-pin and a 4-pin and fill it all up.

I ask because I am having a difficult to troubleshoot problem where occasionally when powering up (not rebooting) from the off state (not sleep or hibernate), the PC will start to power on, and within a half a second a pop is heard in my speakers and it immediately goes powered down again, as if I yanked the plug out of the wall. Hit it again and iot powers on normally.

Power Supply: Antec TruePower New TP750 (~10-12 years old now), running a Ryzen 5 5600 and Radeon RX 6600, with a couple M.2 SSDs, 2 120mm case fans + 120mm CPU cooler fan. The TP750 has powered much more "power hungry" parts in the past.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Quexos Quote  Post ReplyReply Direct Link To This Post Posted: 21 Jun 2023 at 9:33pm
Forgot to mention, the PC and Monitor are being run on a "Tripp-Lite avr750u Line Interactive 750VA 450W" battery backup PSU which I believe to be doing it's job since we get the occasional power flicker and it kept things running while the lights flickered off/on and the digital clocks reset.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote eccential Quote  Post ReplyReply Direct Link To This Post Posted: 22 Jun 2023 at 9:14am
All those connections are there to spread out the load. Since you're running R5-5600, which is fairly low power CPU, you don't need to worry.

Here's how it goes:

Minimum requirement: Half of the 8-pin connector using a 4-pin plug. This is done when your power supply does not have 8-pin plug. It should be enough for any 65W TDP processor.

Typical usage: The entire 8-pin connector is used. The extra 4-pin connector is unused. It should be enough for any "normal" builds.

Mostly overkill usage (major overclock, liquid nitrogen, etc.): Both 8-pin and the extra 4-pin are used.

------------

In your case, I see no reason to use the extra 4-pin connector. If the power supply has multiple 12V rails and the 8-pin and 4-pin are from different rails, I wonder if it can cause issues. If the rails don't turn on exactly at the same time, one rail could affect another rail. But I'm not a power supply expert.

It sounds like you're tripping the over-current protection on your PSU. Since you don't have anything really power hungry in your build, I wonder if the PSU is on its way out. Over a decade is a long time. No electrolytic capacitor lasts forever, you know. Or maybe I am onto something with the previous paragraph.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Quexos Quote  Post ReplyReply Direct Link To This Post Posted: 22 Jun 2023 at 12:07pm
Thanks. I had it in overkill mode then, just in case. I have new Power Supply (XPG Core Reactor 750w) coming in tomorrow now though, so probably will just go with the one 8-pin when Install that. I don't O/C at all, and tend to under-volt if anything. On the Antec TP750, the 8-pin and 4-pin come in the hardwired bundle, so I think they're on the same rail anyway.

One by one I am just eliminating things to find the cause of the "power failure/surge". I put a new battery in my UPS backup yesterday and had another hiccup today, so it's narrowing right in that old Antec TP750.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Quexos Quote  Post ReplyReply Direct Link To This Post Posted: 23 Jun 2023 at 8:34pm
New power supply is in and it is being powered with the one 8-pin CPU power connection (second 4-pin vacant). Been solid through a full day of stopping and starting while playing with Linux, Windows and making backup images from a Macrium rescue disk (usually when I had the power on problem).

It's a little too soon to declare it "fixed" but I am gaining some confidence that it was just the power supply, which would not really be surprising since it was a quality part but ~14 years old.

Thanks again for the info.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Xaltar Quote  Post ReplyReply Direct Link To This Post Posted: 23 Jun 2023 at 9:58pm
Unfortunately even the best built PSUs fail eventually. These days it's relatively
easy to get them recapped. I have done it with a few of my veteran PSUs that
lasted and never gave me issues. I only use them for test units and budget builds
but it's nice to know that they were built right.

Give it a few days of regular use, if all is well by then you can rest easy

Edited by Xaltar - 23 Jun 2023 at 9:58pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote eccential Quote  Post ReplyReply Direct Link To This Post Posted: 23 Jun 2023 at 10:21pm
"These days it's relatively easy to get them recapped."

I was going to mention that. Most people don't bother in, well, cushy countries, but it's not a bad idea to fix stuff and keep using, especially if it's relatively easy to do.

But if you got 14 years out of it, I'd say you've done better than many. :)

Your choice of these big 750W power supplies made me do a double take, though, seeing as how your components are all pretty low power. I've NEVER bought a power-supply past 500W, but I go for the best (Seasonic Prime, etc.). But I'm weird. I mean, who else buys a 5800X3D to run with boost completely disabled? (3.4GHz max). My CPU will never see voltage higher than 1.0V as long as I own it. Laugh.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Xaltar Quote  Post ReplyReply Direct Link To This Post Posted: 24 Jun 2023 at 2:55am
Originally posted by eccential eccential wrote:

But I'm weird. I mean, who else buys a 5800X3D to run with boost completely disabled? (3.4GHz max). My CPU will never see voltage higher than 1.0V as long as I own it. Laugh.


I have had 8 of my 16 cores disabled on my 2950x since about a month after I got it
Why use more power than I need to when 8c/16t is more than enough for all the tasks
I use the system for. I also have my VCORE set to 1.0v and capped my frequency
to 3.5ghz. Power is expensive here. When I need to use the system's full power for
a complex render I can just set my performance profile in Ryzen Master and
restart the system.

As for the recapping, it's becoming more common these days with so many guides on
youtube and how cheap/easy it is to do. You can revive a great PSU and even improve
on it by replacing the caps with higher quality ones than the originals.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Quexos Quote  Post ReplyReply Direct Link To This Post Posted: 24 Jun 2023 at 9:36am
Originally posted by eccential eccential wrote:

Your choice of these big 750W power supplies made me do a double take, though, seeing as how your components are all pretty low power.


I never thought of them as big. I think of 1000+ watts as big.

It's more than I am currently (pun intended) drawing, but I'm of the mind that I should have a little extra, because I'm cynical and figure manufacturers are usually fudging the numbers a bit (some more than others), so If you want an actual 600w PSU, buy an "700w", and because I want it to run "easy" and cool at like 50-60% capacity rather than "hard" at 80-100%. Presumably why I got 14 years constant use out of the last one. Plus to future proof in case (pun intended) 2 years from now all the rage is some new tech graphics card that draws 500w all by itself, or I just decide to turn it into a file server with 20 spinning HDDs or something.

But yeah, I could probably stick a 400w PSU in and be fine.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Xaltar Quote  Post ReplyReply Direct Link To This Post Posted: 24 Jun 2023 at 10:19pm
Originally posted by Quexos Quexos wrote:

I want it to run "easy" and cool at like 50-60% capacity rather than "hard" at 80-100%.


I do the same with my systems. Ideally you want to run at around 60-70% load for
optimum efficiency and cooling. PSU efficiency tends to be at it's peak around these
load levels, depending on the spec. What you don't want is to be running at <90%
or consistently >20%, efficiency is terrible in those ranges. This is less of an
issue today than it used to be with most (good) PSUs offering comparable efficiency
across the spectrum, particularly with 80+ Gold or above. Even here though, keeping
your PSU under lighter load will always equate to a longer lifespan.
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