Raptor Lake Refresh Fast Throttle
Fast Throttle, or per-core thermal throttle, is one of the new overclocking-related features introduced with Raptor Lake Refresh processors. It’s a thermal management technology that enables per-core clock throttling in case of overheating.
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I’m removing the heatsink on top of the Core i9-14900K and will run a CPU-Z multi-threaded benchmark, which is a pretty heavy load. How am I so confident that the CPU won’t just overheat or melt? It has something to do with an Intel thermal management feature called Fast Throttle.
Per-Core Thermal Throttle, or Fast Throttle, is one of the new overclocking-related features introduced with Raptor Lake Refresh processors. It’s a thermal management technology that enables per-core clock throttling in case of overheating.
In this article, I explain how it works and compare it with three other thermal management technologies for Intel processors.
The maximum safe operating temperature is a hot topic in the PC enthusiast community. There are diverging opinions on what constitutes a safe operating range. To the inexperienced eye, it may seem that running at 100 degrees Celsius is utterly unsafe because we’d burn ourselves if we touched something at that temperature.
However, silicon chips are much more resilient to high temperatures. So, the truth is that most, if not all, chips we use in our system are designed to run at that temperature for their entire warranted lifespan. For example, within warranty conditions, the maximum allowed operating temperature for the Raptor Lake Refresh K-SKU CPUs is 100 degrees Celsius.
Of course, despite such temperatures being within design specifications, some users are uncomfortable with this high operating temperature. They wish to operate at a lower temperature. There are four options to customize thermal management for Raptor Lake Refresh K-SKU processors on an ASUS motherboard.
- Intel TjMax Offset
- Intel Thermal Control Circuit Offset
- Intel Fast Throttle
- ASUS Package Temperature Threshold
Let’s go over each technology and explain how it works. But first, a quick word on TjMax.
Tjunction Max, or TjMax, is the CPU’s maximum allowed operating temperature. It is programmed in the CPU registers and is part of the CPU’s official in-warranty specification. The end-user cannot alter this value unless you use a fully unlocked processor like the Core i9-14900K. We’ll talk about that in a minute.
Reaching the maximum operating temperature activates Intel’s Thermal Control Circuit, or TCC. The TCC causes the processor cores and graphics to reduce frequency and voltage adaptively when activated. Adaptively, in this case, means the CPU will adjust the operating frequency until it goes below the maximum allowed operating temperature.
I often rely on this Adaptive Thermal Monitor technology in my overclocking guides to control the CPU performance at the upper end of the thermal range.
Thermal Management Technologies
Intel TjMax Offset
The first thermal management feature is available only to unlocked processors, such as the Core i9-14900K, on motherboards with chipsets allowing overclocking. It’s immediately apparent why: TjMax Offset enables us to adjust the maximum operating temperature above the warranted specification.
The function allows the user to program a TjMax Offset between 10 and 63. This offset is then subtracted from 125 degrees Celsius. So effectively, your customizable temperature range is 62 to 115 degrees Celsius.
When the operating temperature reaches TjMax, the CPU automatically reduces the operating frequency and voltage to keep the temperature below or at the maximum allowed temperature. It does this by adjusting the CPU Core Turbo Ratios according to the CPU’s voltage-frequency curves.
Aside from the processor and motherboard restriction, another essential aspect of TjMax Offset is that it requires a reboot to apply. So, this is not an adjustable setting in the operating system.
You can set the TjMax Offset settings via the Extreme Tweaker Internal CPU Power Management submenu in the ASUS ROG BIOS. The parameter range is 62 to 115 degrees Celsius.
Intel Thermal Control Circuit Offset
Unlike TjMax Offset, our second thermal management feature is available to all Intel processors. Intel Thermal Control Circuit, or TCC, is a hardware-level control tool to manage the CPU operating temperature limit. It is defined as a thermal activation offset to TjMax.
The TCC_Offset parameter determines the actual maximum allowed temperature. By default, the value is 0, meaning no difference from TjMax. However, you can adjust the offset to up to 63 degrees Celsius. Note that you can combine TCC_Offset and TjMax Offset. The TCC_Offset applies to the customized TjMax when using an offset.
When the operating temperature reaches TCC_Offset, the CPU automatically reduces the operating frequency and voltage to keep the temperature below or at the maximum allowed temperature. It does this by adjusting the CPU Core Turbo Ratios according to the CPU’s voltage-frequency curves.
Unfortunately, the option to adjust TCC_Offset separately from TjMax Offset isn’t available on the ASUS ROG BIOS. I suspect that perhaps the same function as TjMax Offset is used to set TCC_Offset on non-K CPUs, but I wasn’t able to double-check that. However, TCC_Offset is adjustable at runtime in the operating system. So, by writing directly to the CPU MSR, we can still test the behavior of the CPU.
Intel Fast Throttle
Intel Fast Throttle is a new thermal management customization feature on Raptor Lake Refresh. You may also see it referred to as Per-Core Thermal Throttle. While Fast Throttle was already present on the original Raptor Lake, we can now manually configure the parameter with the 14th gen Core Raptor Lake Refresh.
For those who want to see this feature in action on 13th gen Raptor Lake, you could try setting the maximum allowed temperature to 115 degrees Celsius using TjMax Offset, then try to overheat the system. The Fast Throttle default configuration is 107 degrees Celsius, so you should see that the CPU cannot reach 115 degrees Celsius.
Fast throttle behaves a little differently than the Turbo Thermal Control. I will illustrate that later on with some charts. Rather than reducing the CPU Turbo Ratio, which reduces the set core clock frequency, Fast Throttle modulates the internal core clocks, which adjusts the effective core clock frequency of the CPU.
Clock modulation is done by turning the clocks off and on at a duty cycle (ratio between clock “on” time and total time). The CPU core runs at the set core frequency when the clock is on. When the clock is off, the CPU core is effectively stalled. A CPU’s “effective clock” is the number of clock cycles over a given period. When clock modulation is active, the CPU effective clock will be lower than the set CPU core clock.
An essential aspect of the clock modulation approach is enabling more fine-grained throttling. Since every P-core and every E-core group has its own PLL or clock generator, the CPU can reduce the frequency of specific cores as opposed to all cores. Additionally, it provides for smaller reductions in frequency during clock stretching. Theoretically, these two elements should yield higher performance when temperature-induced throttling occurs.
However, as we’ll see later, things aren’t as straightforward in the real world.
You can set the Fast Throttle settings via the Extreme Tweaker Internal CPU Power Management submenu in the ASUS ROG BIOS. The parameter range is 63 to 115 degrees Celsius.
ASUS Package Temperature Threshold
ASUS Package Temperature Threshold is another technology to manage the CPU operating temperatures. However, unlike TjMax Offset, TCC_Offset, or Fast Throttle, the motherboard performs the thermal management.
In short, the ASUS motherboard will track the CPU operating temperature during operation. The CPU frequency will be reduced once the temperature exceeds your target temperature. It does this not directly by adjusting the CPU ratio, however. Instead, it uses the Turbo Boost power limit parameters. By lowering the power limits, the Intel CPU will adjust the CPU ratio down on its own.
A caveat to this technique is that the motherboard doesn’t know which power limit to target to stay below the target temperature. So, it needs a more extended period to determine the proper power limit. Additionally, the motherboard is slower to react to changes in CPU temperature than the CPU itself. We’ll get to this when we review the data.
In the ASUS ROG BIOS, you can set the Package Temperature Threshold settings via the Extreme Tweaker Internal CPU Power Management submenu or the Extreme Tweaker AI Features submenu. The parameter range is 30 to 115 degrees Celsius. Make sure to enable Regulate frequency by above Threshold when using this function.
Now that we’re up to speed on the various thermal management technologies let’s get to the test data.
The system we’re testing today consists of the following hardware.
|CPU||Intel Core i7-14700K||540|
|Motherboard||ASUS ROG Maximus Z790 Dark Hero||582|
|CPU Cooling||Noctua NH-L9i-17xx Chromax.black||55|
|Memory||G.SKILL Trident Z DDR5-8400 48GB||200|
|Power Supply||Enermax REVOLUTION ATX 3.0 1200W||250|
|Chassis||Open Benchtable V2||200|
I prepared three tests to compare the behavior of thermal management technologies.
The purpose of the first scenario is to see the thermal management technology behavior when the CPU operates at or above TjMax=100C during the workload.
The purpose of the second scenario is to see the thermal management technology behavior when the CPU operates at or above the custom thermal target but below TjMax=100C during the workload.
The purpose of the third scenario is to see the thermal management technology behavior when only one core operates above the custom thermal target.
I made three test variations for each scenario to isolate the thermal management technology. We look at TjMax Offset, Fast Throttle, and Package Temperature Threshold. Since TCC_Offset relies on the same throttling mechanism as TjMax Offset, we didn’t include it in the test separately.
In each test scenario and variation, the target maximum operating temperature is 80 degrees Celsius. However, the thermal management technology regulating the CPU temperature will be different.
Scenario #1: Unlocked Power
In scenario 1, we only unlock the CPU Turbo Boost 2.0 power limits while maintaining the rest of the default specifications. We make the following observations.
- While the TjMax Offset and Package Temperature Threshold technologies ultimately end up at the same effective clock, the TjMax Offset does so much more gradually. With Fast Throttle, our effective clock is much lower than the other technologies. That will yield a significant performance deficit, as we’ll see later.
- While the TjMax Offset is pretty effective at maintaining a maximum temperature of 80 degrees Celsius, the Package Temperature Threshold has the CPU temperature spike temporarily well above 80 degrees Celsius before adjusting to the temperature target. That’s because it’s slower at detecting the CPU temperature exceeding the target. On the other hand, Fast Throttle cannot maintain the target temperature of 80 degrees Celsius.
- While the Fast Throttle has the lowest effective clock, counter-intuitively, it has the highest core clock. As we’ll see in other charts, it illustrates that the Fast Throttle technology does not rely on the V/F curve but instead uses clock modulation to manage the CPU frequency.
Let’s look at the behavior when we use a configuration that doesn’t cause runaway temperature for the Fast Throttle variation.
Scenario #2: 8P 0E
In scenario 2, we disable all E-cores and set P-cores to 4.5 GHz. This will push the CPU to over 80 degrees Celsius, but not beyond the 100 degrees Celsius TjMax.
We can make the following observations.
- The package temperature now remains below 100 degrees Celsius for all variations. However, while TjMax Offset and Package Temperature Threshold maintain the CPU temperature around 80 degrees Celsius, Fast Throttle is again slightly higher at 83 degrees Celsius.
- The core clock throttling is much less pronounced than in the previous scenario. While the Fast Throttle maintains an average core clock of 4500 MHz, the TjMax Offset and Package Temperature Threshold reduce the set core clock to maintain the target temperature.
- Despite fast throttle seemingly retaining the target core clock of 4.5 GHz, its effective clock is about 1 GHz lower at 3500 MHz. This is the effect of clock modulation. Its effective clock is also lower than the TjMax Offset and Package Temperature Threshold.
We’ll get back to the performance metrics in a little bit. But first, let’s look at what happens when only 1 core exceeds the maximum target temperature.
Scenario #3: 1 Core Load
In this scenario, we run a heavy workload on Core 1 and NOPBench on Core 7. The goal is to get Core 1 to exceed the temperature target. Then, we want to see whether it affects the Core 7 effective clock frequency.
From the data, we can make the following observations:
- With both TjMax Offset and Package Temperature Threshold, we can observe that Core 1 core frequency changes due to throttling also affect Core 7 core frequency. However, we don’t see that difference with Fast Throttle.
- We see the same with effective clock: TjMax Offset and Package Temperature Threshold reduce the frequency of Core 7 even though it’s only Core 1 that exceeds the thermal target. However, the Fast Throttle on Core 1 barely affects the Core 7 effective clock.
Cinebench 2024 Benchmark Performance
Lastly, let’s have a look at the benchmark performance. I use Cinebench 2024 Multi-Thread to evaluate the system’s performance in each of the three variations and for Scenario #1 and #2. We find that using Fast Throttle performs significantly worse when all cores hit the thermal limit. This is in line with what we expected from the test data.
Let’s sum up our findings.
First, let’s emphasize that it’s great that Intel provided us with a new option to customize the CPU performance. It’s always better to have the option than not have it.
Second, the Fast Throttle feature works best when few but not all cores hit the thermal limit. In that case, it doesn’t throttle the frequency of all cores – like TjMax Offset, TCC_Offset, or Package Temperature Threshold does – but only the cores that overheat. In theory, that should provide better performance.
Third, when all cores overheat, the Fast Throttle mechanism appears overwhelmed and shows worse results than TjMax Offset or Package Temperature Threshold. Especially when both Fast Throttle and TjMax Offset are active together, the system performance is much worse than when only TjMax Offset is engaged.
Lastly, the TjMax Offset function is the fastest thermal management technology. That makes sense because it’s integrated into the CPU.
So, what would I recommend in terms of configuration?
Suppose you wish to set a maximum operating temperature lower than the CPU’s specified maximum warranted operating temperature. In that case, I suggest primarily relying on TjMax Offset or TCC_Offset, as both rely on the same underlying throttling mechanism. It is the fastest and most precise in detecting overheating and adjusting the CPU frequency to stay below the desired temperature. The Package Temperature Threshold technology also does its job but is slightly slower in adapting to the overheating processor.
Fast throttle is a bit of an odd one. It looks great on paper, but the performance hit is a bit much in the real world. So, for now, I would configure it the same as TjMax.
Anyway, that’s all for today! I hope the information provided in the article can be of use to you. I want to thank my Patreon supporters for supporting my work. If you have any questions or comments, please drop them in the comment section below.
See you next time!