Question on 12v power connections B550 Pro4

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.

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.

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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.

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.

"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.

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.