Various websites have reported finding the phone's GPU (graphics processing unit) returns a 533 MHz speed number in some benchmark tests while actual clock speed when running games is 480 MHz, Gizmodo.com reported Wednesday.
"This seems to be purely an optimization to produce repeatable [and high] results in CPU tests, and deliver the highest possible GPU performance benchmarks," Web hardware review site Anand.tech said.
Samsung, in response, said the clock speeds vary to optimize graphics performance for different applications.
"Under ordinary conditions, the Galaxy S4 has been designed to allow a maximum GPU frequency of 533MHz. However, the maximum GPU frequency is lowered to 480MHz for certain gaming apps that may cause an overload, when they are used for a prolonged period of time in full-screen mode," it said in a statement.
The Galaxy S4 is designed to run at a higher clock speed on many full-screen apps, and benchmarking apps simply fall into that category, the company said.
However, Anandtech said it found code within the phone indicating the existence of a program called "BenchmarkBooster," responsible for overclocking the device's processors when certain apps are running.
Samsung, in its statement, denied speed changes were aimed specifically at benchmark programs.
"The maximum GPU frequencies for the Galaxy S4 have been varied to provide optimal user experience for our customers, and were not intended to improve certain benchmark results," the company said.
"Samsung Electronics remains committed to providing our customers with the best possible user experience."