I updated my ASUS PRIME Z790-P WIFI from BIOS 1660 to version 1836, and since then my Corsair Vengeance DDR5 kit will no longer boot with its XMP profile enabled. The system falls back to safe mode and returns to the BIOS. It now refuses to run above about 5200 MT/s, even though the same 32GB kit ran at 6200 MT/s for roughly two years without problems.
The memory is a 2x16GB Corsair Vengeance kit, model CMK32GX5M2E6200C36, using Micron ICs. Its XMP settings are DDR5-6200, 36-46-46-100 at 1.40V, and the modules are installed in slots A2 and B2. The system uses an Intel Core i7-14700KF and the current BIOS is 1836; reverting to BIOS 1666 allowed the system to boot at 6200 MT/s again. A previous OCCT memory test at 6200 MT/s ran for 30 minutes with no reported errors, though the CPU reached roughly 78–84°C and briefly recorded a 100°C core maximum.
I also tested another memory kit that appears on the motherboard's QVL, and that kit worked at 6200 MT/s. More recently, I managed to boot this kit at 6000 MT/s by enabling High DRAM Voltage Mode and setting both VDD and VDDQ to 1.40V, but 3DMark then crashed during testing. Could the BIOS have changed memory-training behavior, or could the CPU's memory controller be degrading? I'd appreciate advice on what to test before replacing hardware.
2 Answers
Try testing the kit one module at a time, starting with a single stick in slot A2. If one module works at 6200 while the other does not, that points toward a bad DIMM. If neither does, try clearing CMOS and retraining the memory with conservative settings before enabling XMP again. The fact that another QVL-listed kit works also makes compatibility or marginal memory-controller behavior more likely than a simple slot issue.
A BIOS update may not have damaged the memory itself; it can change memory training, voltage behavior, or the default limits applied to the CPU’s integrated memory controller. However, with a 14700KF, CPU degradation should also be considered. A weakening memory controller can first show up as failure to run a previously stable high memory ratio, followed by crashes even when the system manages to boot.
The 6200 MT/s OCCT result only proves that configuration was stable during that particular test and BIOS state. Since the newer BIOS and the higher-voltage 6000 MT/s setup are now crashing under load, avoid increasing voltage further. Clear CMOS, load optimized defaults, update to a known stable BIOS, test each DIMM separately, and run a thorough memory test at JEDEC speed and then at progressively higher speeds. If the processor is unstable at stock settings or cannot maintain a reasonable memory speed with a known-good kit, contact Intel about a warranty replacement.
I reverted to BIOS 1666 because the problem appeared after updating, and that let the system boot at 6200 MT/s again. But after enabling High DRAM Voltage Mode and setting VDD and VDDQ to 1.40V, tests still crash at 6000 MT/s, so I am also considering the CPU as a possible cause.
I have not tested each stick individually yet. The other kit working at 6200 is what makes this confusing, since my current kit ran at that speed for years before the BIOS change.