Here we present the average clock speed for each graphics card while running the 3DMark Time Spy stress test for 30 minutes. We use GPU-Z to record the GPU core frequency during the Time Spy runs. We calculate the average core frequency during the 30 minute run to present here.
In terms of the clock speed behaviour of the RX 6900 XT, it's very similar overall to the 6800 XT, but we do see it trending slightly faster than the 6800 XT. Where the 6800 XT averaged 2200MHz across our 30 minute stress test, the 6900 XT averaged 2222MHz, so there's only a slight difference between the two GPUs, but it's not bad when we remember the 6900 XT has 512 more cores.