So I recently upgraded my PC's mobo, ram and CPU ( MSI B450M Pro-M2 Max, Ryzen 5 3400G) keeping the old psu that worked fine (300W)
I tested the idle current and voltage of it ( with HWMonitor) and it seems to work fine (5A to 10A). I opened minecraft and it measured 92A.
Note that im using a 4-pin CPU power cable instead of an 8-pin
Will getting a new PSU solve my problem?
Current reporting by monitoring utilities aren't to be trusted unless calibrated. It's common for their reported values to be off and by sometimes wide margins. HWMonitor is also known to be the worst for monitoring Ryzen, with frequently inaccurate readings, unlabeled sensors and sensors that often just don't make sense which can lead to mis-interpretations of what you're seeing.
A new PSU won't solve that 'problem' because it's not likely a problem (although, being 300W and but one 4 pin CPU connector it's likely pretty old and a worthy candidate for updating.)
One thing you could do is get HWInfo64. It has a Power Reporting Deviation readout that attempts to provide an indication of just how far your power reporting is off. You have to calibrate it first, do that by making sure all BIOS settings are STOCK (CPU core multipliers and VCore voltage settings in AUTO) then run a heavy, real-world all core work load. Cinebench20 or 23 are good ones, a free download and easy to start up.
Once running the test workload check the power reporting deviation. It should be 100+/- 10%, if it's way off from that then the motherboard mfr. set up their BIOS presets wrong.
Power is a product of voltage and current. Voltage readings are generally pretty easy to get since they can be made directly but current is very difficult to read without special circuits that are costly to implement and would probably affect board performance so mfr's will do something to infer it. Mfr's often get the algorithm they use for inferring current wrong, sometimes intentionally. That's why you can't trust it until you've calibrated.
There's an interesting writeup about why power reporting is important, how Ryzen uses it and why mfr's are influenced to mis-report it here:
Ryzen CPUs for AM4 platform rely on external, motherboard sourced telemetry to determine their power consumption. The voltage, current and power telemetry is provided to the processor by the motherboard VRM controller through the AMD SVI2 interface. This information is consumed by the processors...
www.hwinfo.com
Another reason to use HWInfo64 is you need to separate CPU current from SOC current. For reference, my 3700X CPU draws ~90A current (my motherboard power report deviation is pretty close to 100%) when running a Prime95 workload; that's an 8 core/16 thread CPU. But the SOC is the GPU part of an APU and they can draw massive power in a 3D rendering workload, so I expect current to be equally high. I'm just not sure how much is normal for that since I don't run an APU.
HWInfo64 makes all those sensor reports very clear so you can sort it out.
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