3DMark Fire Strike was released in 2012, when high-end gaming PCs featured CPUs with 2-6 cores. The Fire Strike graphics engine was designed with a simple threading model utilizing one thread per logical core. As modern high-end gaming CPUs can have 16 or more logical cores, and because Fire Strike's threading model wasn't tuned for such processors, you may see reduced graphics scores on systems using CPUs with greater than 8 logical cores with a modern high-end GPU.
UL Solutions does not recommend running 3DMark Fire Strike on new CPU architectures and instead recommends the use of a newer 3DMark test with a more modern threading model, such as Speed Way, Time Spy Extreme, or Wild Life Extreme.