I have a 5080 that seems perfectly happy with the VRAM at +3000 (36 Gbps) but I thought I would test the VRAM with MemTest Vulkan since GDDR7 has on chip ECC. I've read multiple posts where people say "bandwidth should increase and if it decreases, ECC is kicking in" but nobody explains which of the output values I should be looking at.
What I did was run the test 3 times at each VRAM clock: Stock, +1000, +2000 and +3000 and then screenshotted the results of each so I could flip through them to compare. Here is a gallery of results. As you can see, as the clock increases, the write bandwidth increases, but the checked (or what I assume is read bandwidth) seems to fall slightly and bottom out after the first iteration.
There is no way ECC is kicking in at +1000 considering the 5080 has underclocked 32 Gbps VRAM modules so +1000 is still actually within spec.