[SOLVED] Is max TDP *really* the only thing that matters about the motherbaord when upgrading the CPU?

[ZivDero]

I've always been a bit at a loss when thinking about motherboards. RAM, CPUs, GPUs - they're all not too hard to judge about even not being a giant enthusiast knowing every single detail. But motherboards? Yeah, sure I can make sure that my MB has the right socket, perhaps update the BIOS to support the CPU if necessary, check that I have the right pin headers and enough PCIe slots, but how can I make sure that I don't get "too little" motherboard?

Right now I'm using an MSI B450M PRO-VDH MAX with a Ryzen 5 3600, which has a TDP of 65W. Technically, the MB claims to support Ryzen 9's. So how can I make sure in this case, and in general that if I were to upgrade my CPU to almost double the TDP (65 to 105) by putting in the lastest and greatest, that the power delivery is going to be sufficient? I've watched various repair videos and they sometimes say something about how the power delivery looks, whether it's enough or not, but I can't tell anything by just looking at the MB.

 

[drea.drechsler]

... which has a TDP of 65W. ..

The important information for a motherboard would be current handling capability of the VCore VRM and resulting voltage stability under heavy load. TDP has very little to do with that as it's only an indication of the thermal output potential of the CPU when operated in stock settings and meant to be used as guidance for selecting a heat sink. It has next to nothing to do with the electrical power a CPU needs to run stable.

That board has a relatively weak VRM with a relatively small heatsink on the VCore FET's. It's current handling is probably on the lower side and will probably have poor voltage stability in extremely heavy workloads on a 12 or 16 core CPU. But luckily, when operated stock Ryzen CPU's are also very tolerant of wildly unstable voltage so you would probably never notice it.

What you are much more likely to notice are extremely high VRM temperatures which, should they go above 110-115C or so, results in throttling the CPU clock till it cools off. But that will only occur under sustained, extremely heavy all-core workloads like video rendering so gaming won't likely do it. What's important to know is how you plan on using the system.

It would also present problems with a fixed voltage/fixed frequency all-core overclock. But Zen 2 and Zen 3 CPU's don't benefit from that unless sub-ambient cooled.

So in general that board would be a poor choice if setting up a new-build system with a Ryzen 9 processor. But since you have it, go ahead and try it with your processor upgrade to see how it works. MSI lets you monitor VRM temperature so keep an eye on it while doing what you normally do and if it stays under 90C or so then you'll be fine. If it runs 95-105C in daily use then you might consider a new board since it will degrade sooner. Don't worry about VRM temperatures in benchmarks or stress tests as all that's necessary is to pass it: it's the daily use temperatures that matter.

 

[ZivDero]

The important information for a motherboard would be current handling capability of the VCore VRM and resulting voltage stability under heavy load. TDP has very little to do with that as it's only an indication of the thermal output potential of the CPU when operated in stock settings and meant to be used as guidance for selecting a heat sink. It has next to nothing to do with the electrical power a CPU needs to run stable.

That board has a relatively weak VRM with a relatively small heatsink on the VCore FET's. It's current handling is probably on the lower side and will probably have poor voltage stability in extremely heavy workloads on a 12 or 16 core CPU. But luckily, when operated stock Ryzen CPU's are also very tolerant of wildly unstable voltage so you would probably never notice it.

What you are much more likely to notice are extremely high VRM temperatures which, should they go above 110-115C or so, results in throttling the CPU clock till it cools off. But that will only occur under sustained, extremely heavy all-core workloads like video rendering so gaming won't likely do it. What's important to know is how you plan on using the system.

It would also present problems with a fixed voltage/fixed frequency all-core overclock. But Zen 2 and Zen 3 CPU's don't benefit from that unless sub-ambient cooled.

So in general that board would be a poor choice if setting up a new-build system with a Ryzen 9 processor. But since you have it, go ahead and try it with your processor upgrade to see how it works. MSI lets you monitor VRM temperature so keep an eye on it while doing what you normally do and if it stays under 90C or so then you'll be fine. If it runs 95-105C in daily use then you might consider a new board since it will degrade sooner. Don't worry about VRM temperatures in benchmarks or stress tests as all that's necessary is to pass it: it's the daily use temperatures that matter.

Thanks! Actually, I do do quite some video rendering, even if not on a daily basis, so I guess I should look into something more advanced. How DO I just the VRM's capability, though? Doesn't seem like the manufacturers are particularly verbose about what they put on.

 

[drea.drechsler]

... Doesn't seem like the manufacturers are particularly verbose about what they put on.

That's a common complaint about motherboards purchases. You might compare sizes of the heatsink and how well finned they are. More mass is better and fins provide plenty of surface area to transfer the heat to surrounding air. It's a fair guess they put a bigger heatsink on a board with higher phase count VRM.

Some motheboard vendors give you the phase count but that can be misleading without knowing if it's discrete FET's or DrMOS power stages under the heatsink. Even going to the top of the line won't always help because you'll be paying for a massively over-capable VRM even for 5950X's.

LTT used to provide a tier list of AM4 motherboards at the below link. Hopefully it's sufficiently up-to-date to help.
https://docs.google.com/spreadsheets/d/1Smj5dh97n32wJqm5dkdDcQt8ID7vH52-lKzaaXUUQx8/edit#gid=0

Last, as I said you might go ahead and try your new CPU on the board before committing to upgrading that too, just watch the VRM temperature. A good utility for that is HWInfo64 as you can put the sensor reading in a chart on the desktop to watch how the temperature is trending throughout a rendering.

 

[ZivDero]

That's a common complaint about motherboards purchases. You might compare sizes of the heatsink and how well finned they are. More mass is better and fins provide plenty of surface area to transfer the heat to surrounding air. It's a fair guess they put a bigger heatsink on a board with higher phase count VRM.

Some motheboard vendors give you the phase count but that can be misleading without knowing if it's discrete FET's or DrMOS power stages under the heatsink. Even going to the top of the line won't always help because you'll be paying for a massively over-capable VRM even for 5950X's.

LTT used to provide a tier list of AM4 motherboards at the below link. Hopefully it's sufficiently up-to-date to help.
https://docs.google.com/spreadsheets/d/1Smj5dh97n32wJqm5dkdDcQt8ID7vH52-lKzaaXUUQx8/edit#gid=0

Last, as I said you might go ahead and try your new CPU on the board before committing to upgrading that too, just watch the VRM temperature. A good utility for that is HWInfo64 as you can put the sensor reading in a chart on the desktop to watch how the temperature is trending throughout a rendering.

Will do! Thanks a lot for the advice.

 

[TerryLaze]

MSI lets you monitor VRM temperature so keep an eye on it while doing what you normally do and if it stays under 90C or so then you'll be fine. If it runs 95-105C in daily use then you might consider a new board since it will degrade sooner. Don't worry about VRM temperatures in benchmarks or stress tests as all that's necessary is to pass it: it's the daily use temperatures that matter.

This is also a reason that down draft coolers are preferred for cheaper mobos, they help with keeping the VRMs cooler.