About a month and a half ago (September 27th), AMD stepped forward into their new AM5 era, with the launch of the Ryzen 7000 “Raphael” CPUs. And step forward it was, with all four initial offerings substantially outpacing the previous years’ Ryzen 5000 CPUs (minus sometimes the 5800X3D but that one is special). AMD claimed huge improvements in both raw performance and performance-per-watt efficiency over the previous generation, but unfortunately those efficiency improvements were somewhat hidden behind the CPUs’ increased power draws. And along with those power numbers, AMD also changed the CPUs’ thermal behavior, which greatly increased the (visible) operating temperature.
That behavior change is actually rather interesting, but it has been a cause of concern for both users and technical support specialists. A CPU’s maximum clock speed (and thus to some extent its relative performance, but clock speed is not everything) is limited by one of three things: either the CPU’s power limit, the CPU’s operating temperature, or the design and construction quality of the CPU itself. Higher power limits increase clock speeds but also increase temperatures; higher operating temperatures tell the CPU to reduce clock speeds to keep itself safe; and the CPU’s quality plays into all three (power, temperature, and clock). However, there are diminishing returns on power: doubling power does not double performance, it may only lead to a few percent increase alongside a huge increase to heat.
Ryzen 1000-5000 were all constrained by fairly conservative power limits, which is what led to their amazing efficiency and well-contained temperatures (especially relative to the infamous AMD Bulldozer series of 2011). In contrast, because of their raised stock power limits, Ryzen 7000 is nearly universally constrained by temperatures, with all Ryzen 7000 CPUs consistently reading 90-95 C under load. AMD has stated that this is actually intended behavior, and their new CPUs are all supposed to run at 95C for long periods of time (and the true overheat-shutdown point is 105C). However, that does come at the obvious expense of power consumption, and heating up your bedroom (and sure that one’s probably fine for winter but it might not be what you want year round).
Now, as a disclaimer, the previous several paragraphs are meant to be more informative for a general audience. After this point, the following text contains information which is more targeted towards advanced users who are more comfortable with testing and prodding at their hardware, overriding official specifications, and seeing just how much their hardware can do, rather than just allowing it to run “as the devs intended”.
The below section is also going to focus specifically on the Ryzen 9 7950X, as it is the one most dramatically affected by power limits, however the features discussed are present on all Ryzen 7000 CPUs and motherboards.
In the past, one of the big hot topics in enthusiast computing has been overclocking, and how to squeeze just a little more performance out of a system without cooking it or damaging something. But with Ryzen 7000, that story changes. Ryzen 7000 already effectively run themselves at their safe thermal limits in order to clock as fast as they can. So the new question becomes, How can we walk back the power and temperatures, without drastically slowing down the system?
Enter Eco Mode. Eco Mode is a BIOS-level feature set included in AMD motherboards. It actually goes back to 2019 and Ryzen 3000’s launch, but given the great efficiency of past Ryzen CPUs it wasn’t a big deal. Eco Mode is a set of preset numbers which are fed into another AMD feature called Precision Boost Overdrive (PBO). PBO is a set of control settings on how much power the motherboard is allowed to feed into the CPU.
Ryzen 7000 Eco Mode comes with three presets: 170W, 105W, and 65W. (And while these numbers look like power numbers in watts, they have no relation to actual CPU power consumptions.) 170W eco mode is actually the stock preset that the Ryzen 9 7900X and 7950X run at; 105W eco mode is the stock preset that the 7700X and 7600X run at. 65W eco mode is roughly in line with the power of the Ryzen 5 CPUs of the last five years.
It took a few weeks for benchmarks to start being run and published on eco mode versus stock settings, but now we’re starting to see those numbers and how impactful they can be, and some of those numbers get really interesting.
For a 7950X, the drop in performance from the stock 170W tier to the mid-grade 105W tier is actually minimal. At worst, it translates to roughly a 5% slowdown in long-duration render times in Blender or similar software, and in most cases the change is almost nonexistent. However, the power drop is stunning, knocking the original 260W actual CPU power draw, down to merely 160W. And what’s particularly fascinating is how it does it: on the full 170W profile, the 7950X maintains completely flat 5.1GHz clock across all cores, while on the 105W reduced profile, the 7950X drops down to holding 4.8GHz, but it will jump back up to 5.1GHz for split seconds of time. The effect that has, is that because the CPU is still allowing itself to reach its full clock speeds for a few moments when it has the opportunity, any software that does not apply a completely flat workload to the system (i.e. any gaming, or most software that isn’t Blender or the like) will experience far less of a slowdown than the “6% slower sustained clock speed” would say at face value. (Once again, clock speed is far from everything.) And this is where that claimed uplift in performance-per-watt efficiency is shown and realized.
Now, on to the 65W tier. At that point, a 7950X will start to get actually held back pretty badly. The 65W profile pulls the 7950X’s actual power draw down to only 90W, only just more than ⅓ of its base power. However at that point the loss in clock speeds starts to add up, dropping from a static 5.2GHz to a fluctuating 3.8GHz to 4.2GHz. And while I did just say clock speed isn’t everything, that 18-25% drop in clock speed is enough for most editing and production software to feel it. (Generally that “feel it” is closer to a 10% drop than a 25% drop, and gaming FPS still doesn’t feel it at all; but it’s also enough of a drop that it pulls the 7950X down closer to a 7900X in performance. Granted it is still getting 7900X performance for 45% of the max power, at 90W vs 200W, but it is a pretty harsh limit on the hardware.)
There are a couple of conclusions that can be drawn from this. Ryzen 7000 CPUs are very capable pieces of hardware. However, they are also designed to push up against their limits much more than past Ryzen CPUs were. That limit-pushing gets them a little bit of extra performance but it comes at the cost of the efficiency that earlier Ryzen was famous for. Precision Boost Overdrive and the Eco Mode presets give us the means of reclaiming that efficiency, and in many circumstances that reclamation does not even significantly harm system performance. However, there is also a point where reducing the heat comes at too steep a cost, and dropping from 170W to 65W may be a bit too far.
So, let’s say for the sake of having a story to tell, that you’re concerned about your shiny new Ryzen 9 7950X running at 95C constantly. And while AMD has said this is supposed to happen, you still don’t like seeing it and you want to tone down the heat a bit. How do you do it?
[As a disclaimer regarding VRLA Tech’s warranty policies, Ryzen Eco Mode is not overclocking, and thus enabling Eco Mode via presets to decrease your CPU’s power limits will not void your VRLA Tech PC’s warranty.]
The following screenshots show an ASUS ROG Crosshair X670E Hero motherboard and a Ryzen 9 7900X; however the settings will look similar on other boards.
Reboot your computer and enter BIOS. Once in BIOS, go into Advanced Mode, then in the Extreme Tweaker tab find Precision Boost Overdrive.
In the Precision Boost Overdrive line, select AMD Eco Mode
After setting Precision Boost Overdrive to AMD Eco Mode, a new line of options called AMD Eco Mode appears. That line allows you to choose which of the three power profiles to choose.
As a reminder,
Auto will make no changes to system behavior
170W is the default mode for the 7950X and 7900X
105W is the default mode for the 7700X and 7600X
65W is lower power than Ryzen 7000 default settings
After selecting a power profile, press F10 to Save Changes and reboot. These should only be two settings changed.
Your CPU will now run at the lower power limit, and thus at substantially lower temperatures.
To return the CPU to its original behavior, change both the Eco Mode and PBO settings back to Auto.