Introduction
CPU-Z is a very useful free utility that has been around for many years. It is usually used to gather detailed information about your CPU, motherboard, BIOS, RAM, and GPU configuration. Another valuable use case for this tool is using CPU-Z for load generation.
The focus of this post is using CPU-Z for load generation, either with all threads or a limited number of threads. This is something I have been doing a lot of lately.
The CPU-Z Benchmark
The Bench tab on CPU-Z lets you run a twenty second CPU benchmark that first tests your CPU multi-thread performance and then tests your CPU single-thread performance. You can choose from three different benchmark tests, but most people seem to use the default Version 17.01.64 test. You run the benchmark test by pressing the Bench CPU button.
Running the Bench CPU test gives you a very quick and dirty view of your single-threaded CPU performance (how fast is your CPU) and your multi-threaded CPU performance (how much CPU capacity do you have).
Using CPU-Z For Load Generation
There is also a Stress CPU button that will run the CPU Multi Thread test indefinitely. By default, this test will immediately peg all of your CPU logical cores at 100%. Depending on your hardware, this will usually generate a lot of noise and heat. It will also use a lot of electricity.
Stressing your CPU helps you figure out how effective your CPU and case cooling are and whether you see any clock speed decreases due to power or thermal throttling.
Another option for this test is to purposely limit the number of logical processors (threads) used in this test. If you check the Threads checkbox, there is a dropdown that lets you choose how many threads are used for the test. The lowest you can choose is 1 thread. After that, it will go up in even number increments until you reach the maximum thread count for your system.
My AMD Ryzen 9 5950X processor has 16 physical cores and 32 threads (16C/32T), so I can pick 1 thread, 2 threads, 4 threads, etc., going up to 32 threads. This is what it looks like on my system when it is limited to 8 threads.
Windows Task Manager
If you look at Task Manager, you will see which logical processors are being used by the test. You can also see the average clock speed of your logical cores. Other tools, such as CPU-Z or HWiNFO64, will give you more accurate clock speed info for each processor core.
One thing you should know is that Windows Task Manager shows the total CPU utilization across the entire machine on the CPU page of the Performance tab. If you go to the Processes tab and sort by CPU utilization, you can see how much CPU is actually being used by CPU-Z.
Using this method lets you generate a pretty precise and repeatable partial CPU load on your system. This can be useful if you want to measure something else while your system is under different levels of CPU load.
Hyperthreading
Another thing to consider is how Intel Hyperthreading (HT) and AMD SMT work. When either of those is enabled, your physical processor cores are logically divided into logical cores, so Windows will see twice as many cores. A 16 physical core processor ends up having 32 logical cores.
Many people mistakenly assume that this gives you a doubling of your CPU capacity, but this is not the case. The actual CPU capacity increase is usually about 25%. There is no single-threaded performance increase with HT or SMT.
I have more details in this post: What is the Difference Between Physical Sockets, Physical Cores, and Logical Cores?
Sensor Information
You can use GPU-Z to see the temperature of your CPU (and GPU) when your system is idle and under different amounts of load. This lets you evaluate how effective your cooling system is and can help you understand whether you are seeing any thermal throttling.
Generally speaking, once most CPUs get above about 80C, they start to see thermal throttling. This means that the CPU clock speed is reduced to try to limit the CPU temperature, which obviously hurts your performance.
You can also get extensive temperature sensor information from HWiNFO64.
I have a couple of videos about how to use these tools.
Final Words
When you use this method, you should try it with the different core counts that you have to choose from, so that you better understand how much CPU load you are actually generating. You can’t just assume that using 50% of your cores will generate a 50% CPU load (it is usually higher).
If you have any questions about this post, please ask me here in the comments or on Twitter. I am pretty active on Twitter as GlennAlanBerry. Thanks for reading!