Ryzen CPU current draw in 2000 and 3000 series

[Jonotallica]

How many amps does Ryzen 2000 series draw in terms of VRMs on the motherboard?  I saw something in the last few days about 100A but can't remember where that was.  Or if that's reliable info.

 

No one knows about Ryzen 3000 series, but based on the motherboard specs of X570 it seems like it's going to be a lot more.  But does anyone have any guesses as to how much more.  For example, the Ryzen 3700X or 3800X shouldn't be THAT much more than the 2700X right? 

 

But then, if you add 12 or 16 cores it starts to make more sense.  But does it scale equally, or does it ramp up?  For example.. a 12 core running the same frequencies as 2700X.. will it be using 33% more current.. or more than that?  If it's true that 2700X draws 100A through the VRM.. does it mean that the 16 core will be using 200A or will it be a lot more?

 

I know that this information will be easier to talk about in the next few months when benchmarks and other info comes out into the public, but does anyone have any guesses based on previous experience with earlier systems?

[Mira Yurizaki]

The maximum amps a Ryzen 2700X is allowed to draw period is 115A. Otherwise it typically hovers around 60A continuously and spikes up to 90A.

 

Estimating power draw is not as easy as it may seem. There's two factors in play here. The first is the I/O portion of the processor and the Infinity Fabric eat up a non-trivial amount of power. The second is the more cores the processor uses, the more it limits how fast the entire processor can operate at. For example, this is the power consumption trend for Threadripper 2990WX (from https://www.anandtech.com/show/13516/the-amd-threadripper-2-cpu-review-pt2-2970wx-2920x/2)

 

While the power consumption for cores starts off linearly (double the core load roughly doubles the core power consumption), it starts to taper off at 8 cores before essentially plateauing at 17.

 

A similar thing happens even with the 16 and 12 core variants

 

 

EDIT: Basically speaking, the TDP plus about 10% is what you can expect the processor to use power wise (at least for AMD's processors). Since the processor typically runs at 1.35v, you can use some math to figure out how many amps the thing will suck.

Edited June 10, 2019 by Mira Yurizaki

[Jonotallica]

Interesting.. thanks for that reply.  Hopefully I understood it properly.  So it's TDP I should be worrying about?

 

My motherboards VRM is 8 phase and each phase can handle 40A, but it's really inefficient at full load like that.  But at 25A per phase, it's at peak efficiency (if I'm remembering right).  If it's not peak efficiency, it can at least run at 25A very stable and smoothly.  So if I have all of this right, 200A is the limit I should probably be trying to stay under.  Giving some headroom for those possible spikes that go higher.

 

So at 1.35V.. with a total power draw of 270W.. the current would be 200A.  So regardless if I am using an 8 core, 12 core, or 16 core.. if I'm running 1.35V I should be looking to stay under 270W using AIDA or some other measuring software.  When using this motherboard.  Do I have all of this right?

 

I don't know if I'd ever want to be running the CPU that high.. regardless of what cores it has, as it seems pretty inefficient but just trying to explore the hypothetical limits.  Also.. if I'm running at a more sensible TDP.. for example 125W or 180W.. it seems this motherboard could handle this with no problems at all?  Regardless of whether it's an 8, 12 or 16 core?

[Mira Yurizaki]

17 minutes ago, Jonotallica said:

So at 1.35V.. with a total power draw of 270W.. the current would be 200A.  So regardless if I am using an 8 core, 12 core, or 16 core.. if I'm running 1.35V I should be looking to stay under 270W using AIDA or some other measuring software.  When using this motherboard.  Do I have all of this right?

 

I don't know if I'd ever want to be running the CPU that high.. regardless of what cores it has, as it seems pretty inefficient but just trying to explore the hypothetical limits.  Also.. if I'm running at a more sensible TDP.. for example 125W or 180W.. it seems this motherboard could handle this with no problems at all?  Regardless of whether it's an 8, 12 or 16 core?

If AMD is using TDP as the upper power limit, plus some change, then that's the maximum power draw you can expect to see. So far for the AM4 platform, no processor has a TDP higher than 105W.

 

And digging around just to make sure my numbers were more or less correct, AMD claims the average vCore for the 2700X is 1.25V rather than 1.35V (https://community.amd.com/thread/228343). So even if we are hitting the maximum power limit of the CPU, that's still around 85A on average.

 

I wouldn't worry about amperage spikes too much. They're just that, spikes. Worry more about average/continuous current ratings.

Edited June 10, 2019 by Mira Yurizaki

[Jonotallica]

But when it comes to overclocking, TDP is always much more than they say.  It seems that both AMD and Intel find a way to define their own TDP and in a way it's like a made up number.  For example.. the flagship Intel i9.  If you want all cores to 5ghz.. it's more like 200W+.

 

For AMD, their TDP is related to the peak power under boost, but I've still seen people saying that for 2700X.. it's closer to 125W.  Others say 115W.  But it's always more than what they say on the box.  It's just that I think AMD lies less, compared to Intel.  And that's without factoring overclocking.. because if you have the right cooling solution.. it's natural to want to push the limits of voltage, and temps to see how much further you can push.  I usually don't like to do this because I like 24/7 stability.. and lower temps.. and for the chip to last a long time (for resell or to use for a spare PC) but it's still nice to see where the limit and headroom is.  And then to back off from that for long term use.

 

I guess it will be ok with stock AMD clocks for all of the 3000 series.. if I always look towards TDP.  And with AMD, they don't overclock very much anyway.  The all cores can be raised a bit, but the peak boost clock with 2 cores usually can't go much higher.  I guess the overclocking thing is impossible to answer because it could be extreme water cooling, a decent air cooler, or a stock air cooler.. and the voltages and temps can vary so wildly.

 

If I bought a 12 or 16 core I wouldn't expect to be overclocking much anyway.. since it will already be a powerful CPU.  I haven't even built my 2700X system yet.. I'm just trying to plan for the future, with future upgrades.  I appreciate your replies.  I won't know 100% until testing in the real world.. but at least.. it seems like my motherboards VRM shouldn't be a big bottleneck or anything.  It also makes me think that X570 VRM is super overkill unless you are trying to break overclocking records.  My main concern in making this post.. is that I would like to use this motherboard for the next 4-5 years.. and don't want a CPU upgrade to shorten the life of the board.  The ability to change CPU and keep the same motherboard is one of the benefits of AMD.  I might not even get a 16 core, but it would be nice to know that if I need to.. that I can (and just don't overclock it too much).