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Overclocking the RTX 5090 Lightning Z is no different in principle than on any other Blackwell card. Fire up MSI Afterburner, raise the power limit to the max, then start raising the clock slider until you start seeing graphical artifacts or game crashes. Once you hit that limit, dial back the slider step by step until it’s stable.
After several rounds of this process, we arrived at an Afterburner clock offset of +143 MHz, which results in a mean real-world clock of 3149 MHz across all the games and settings we tested. That’s just a 132 MHz increase over the 3017 MHz mean clock speed we observed from both the stock and OC BIOSes.
To be fair, this isn’t anything new for GPU overclocking these days. Nvidia’s GPU Boost algorithm already extracts most of the performance available from any extra power and thermal headroom that a given card might offer. But with a cooler and power-delivery subsystem this extreme, I think you can forgive me for expecting a bit more.
We were also slightly disappointed to see that, despite the RTX 5090 Lightning Z’s exotic feature set, it’s still subject to the same +375MHz GDDR7 overclocking cap that every other RTX 5090 has. Raw GDDR7 memory bandwidth doesn’t seem to limit Blackwell performance as GDDR6 and GDDR6X might have for past Nvidia GPUs, but given this card’s extreme DNA, I was once again expecting that we might have seen this cap lifted.
