Yes, and it's also complicated by the translation to micro-ops with out of order dispatch and instruction retirement. I remember seeing one statement saying th

Yes, and it's also complicated by the translation to micro-ops with out of order dispatch and instruction retirement. I remember seeing one statement saying this is now a complicated enough system that the number of cycles it takes to execute a block of code is literally chaotic in the sense that small changes to initial conditions cause large changes in the number of cycles to complete. A butterfly effect, possibly triggered by whatever the kernel chose to do a millisecond before your code runs. Throw in changing clock rates based on the temperature of the CPU. If your code efficiently uses the ALUs / cores in the processor, it can get hot and slow itself down.