Most everyone who bothers learning the basics about computers will know that today's CPUs and APUs from Intel and AMD have dynamic overclocking technology. What they might not know is that down-clocking happens as well, for AMMD chips at least.
Then again, it's not as though Advanced Micro Devices wants people to know about it, saying it is a minor problem that almost never arises.
Nevertheless, the folks at X-bit Labs have discovered that, under heavy loads that cause the processor's TDP (thermal design power) to go above the allowed level, the clock speed of the CPU cores drop below the base.
This negatively affects performance to an extent that was never intended.
The AMD A10-5800K APU was used in a test. It has a base clock frequency of 3.8 GHz and a Turbo Core level of 4.2 GHz.
When subjected to a high multithreaded load, however, the clock drops not to 3.8 GHz but to 3.4 GHz. Other Trinity chips do similar things.
The Linpack benchmark has revealed the issue, though various video encoding apps and 3D renderers have revealed the same phenomenon.
In response, Advanced Micro Devices has stated that it knows of the problem, but it crops up very rarely, as there are few programs that subject processors to the same toil as Linpack.
“Linpack is one of the few synthetic applications that may exceed the de-rating defined for our TDP. In the synthetic instances where base frequency causes our APU to run above its TDP, the part will throttle down to a frequency below base,” the company said.
“Similar to Intel, thermal design power (TDP) is a realistic power target for partners to use in order to provide the best balance between cost and performance. However, as stated above, some unusual and synthetic workloads can cause a thermal event where our APU briefly drops below the base frequency.”