Question There's no option to undervolt Ryzen 5 3500X in the BIOS ?

[VeeK]

Hi there. I hope undervolting questions are permitted in this category,

I'm upgrading my computer and want to use my current rig as a home server to run a NAS. The CPU is Ryzen 5 3500X and motherboard is MSI B450M Pro-VDH Max with latest BIOS installed. As a NAS server, the performance requirements are minimal and it needs to run 24/7 so I was wondering if I can undervolt it to reduce its power consumption and save some money on electricity. Currently it is drawing around 80W on idle. Like I said, performance sacrifice is acceptable.

I saw tutorials on how to do this but in my own BIOS I couldn't find the relevant option in Precision Boost Overdrive. It seems I can only set clock speeds but not voltage. If someone could point me in the right direction, I would appreciate it.

Here are some pictures:
https://drive.google.com/file/d/1UtquVxfu7GhW1MY3stohZ82hDF-9UAfj/view?usp=sharing

20250630_130221.jpg

drive.google.com

 

[Lutfij]

Disable PBO and see if that helps bring down your power draw. Have you tried working with AMD's Ryzen Master and tweak things there?

 

[Ralston18]

Not questioning the suggestion to disable PBO, etc..

However, I will ask about power consumption.

Certainly in agreement with wanting to reduce power consumption but I would really be interested in quantifying the power savings per se.

How much of a performance hit would there actually be?

What NAS Server software is being used?

Just trying to get a sense of any trade-offs that may be involved.

 

[VeeK]

@Lutfij I can't use Ryzen master because this system will not run Windows. I will look into PBO before messing around with it.

@Ralston18 I'm planning to use TrueNas and Jellyfin on it. Your other questions are not clear to me.

 

[Ralston18]

The underlying question is how much power will actually be saved?

Are the tweaks (PBO and others, if any) worth it?

How much power is being drawn when the NAS is in full use (not "on idle")?

How much time will the NAS be in full use during a 24 cycle?

Electricity is generally billed per kWh.

My current electric bill is shows my kWh rate being $0.12 (USD).

However, with added delivery fees and taxes the end result is $0.205 per kWh.

Will some NAS power saving tweak really save money?

= = = =

Again, all in favor of saving energy and all of the resulting benefits.

I favor a different approach.

My suggestion is to start off by simply running the NAS "as is" without any power saving configuration changes.

Get a sense of the overall performance and actual energy usage over time and useage.

[At the same time, save energy elsewhere - swap in some LED lightbulbs somewhere.]

My thought is that the first objective should be to ensure that the new NAS is up and running well and remains so over time.

Then, knowing that, try tweaking power settings etc.. You may or may not actually save energy and I would keep a log on power consumption vs. performance for awhile.

If things go amiss you will be able to roll back the tweaks.

Very likely there will be some trade-offs involved with any changes that you make.

Bear in mind that BIOS changes, OS changes etc. will likely cause some problems sooner or later.

Bottom line: Get the NAS operational first. Then move on to the energy saving objective if that objective remains a viable and measurable requirement.

 

[VeeK]

That does make sense. Alright. I'll set it up and observe for a few weeks before making any changes.

Just curious though, does my setup support voltage reduction at all? If so, where are the options? I'd hate to setup everything again if I find out the power consumption is too high and there is no way to reduce voltage. If there is no option, I'd consider getting a used low power PC instead and sell this one.

 

[CountMike]

Actually most saving would be in heat output. Automatic PBO settings just allows more/full power to be used when needed, at low CPU usage it does nothing. That also regulates top performance/boost.
For voltage control it's best to use CO (Curve Optimizer), you can find it in PBO section in BIOS, usual settings are negative between -10 to -30 but you have to experiment with it and test, higher numbers may cause instability at low loads.
Other than that, you could limit CPU frequency to something acceptable to you. That would also limit voltage and power and with those also heat output. If for instance, base frequency of 3.6GHz is enough, then limit it to that or even lower.

 

[VeeK]

I think I've found the right option under Voltage settings. I have set the Offset mode to [-] (negative) and Offset voltage to 0.1. So far its stable, I'll test it with my TrueNas setup.

I don't think I have the Curve Optimizer. I don't see it anywhere.

https://drive.google.com/file/d/1ZNZkg7qbCnSlJju822U-u1cvWy9ZeKSf/view?usp=sharing

 

[VeeK]

So interesting news. Second time around I changed the CPU ratio to 25 and Voltage offset to 0.2. The compute stopped posting. I had to reset CMOS to get it back. Its all good now but I'm scared to make changes.

What did I do wrong? I was hoping I'd limit the CPU to 2.5 Ghz.

 

[CountMike]

So interesting news. Second time around I changed the CPU ratio to 25 and Voltage offset to 0.2. The compute stopped posting. I had to reset CMOS to get it back. Its all good now but I'm scared to make changes.

What did I do wrong? I was hoping I'd limit the CPU to 2.5 Ghz.

Too much of voltage offset, over 0.1v is rare to achieve, limiting frequency is not the problem.
Typically sparse MSI manual, can't find exact BIOS settings but CO is usually within PBO>OC settings.