Don't use 1.35V DIMMs on a 1.2V CPU.

Probably not. That extra 0.15V might not fry your chip immediately, but it’s outside the spec, and that’s where trouble lives.

The CPU’s memory controller is rated for 1.2V max. Running RAM at 1.35V means you’re overvolting the IMC (integrated memory controller). Some boards will let you do it, some won’t boot, and some will degrade the CPU over weeks or months. You might get instability, corruption, or a dead chip. The RAM itself might be fine, but the CPU is taking the hit.

If you already own the sticks, check if they have an XMP/EXPO profile that drops to 1.2V at lower speeds. If not, don’t force it. The performance gain from slightly faster RAM isn’t worth replacing a CPU.

Future you will not thank you for this experiment.