I have just upgraded from a Strix X299 & 7820X to a Strix Z590E & 11900K. When the system boots from cold, it starts for about 2-3 seconds, stops, then restarts and boots normally. This issue only happens when the PC has been switched off at the plug and it’s the first boot. If I restart or shut down then start, no issues. I’ve tried with all USBs removed, different drives, re-seated all components, flashed to the latest BIOS, reset to defaults, but it’s the same.
I’ve videoed the boot up and it appears to be the same set of codes before it restarts. It’s difficult to be sure i’ve logged the codes correctly as the speed that the display changes makes it look like other letters/numbers:
00 Red CPU LED illuminates 7F 31 Red CPU LED switches off 08 Yellow DRAM LED illuminates 18 25 27 5F (sometimes) Yellow DRAM LED switches off 00 System reboots
There are multiple clocks in a system (CPU, IMC, memory, etc.), with a variable tick/tock initialization from start-up to start-up, a wide variety of signal pathways and variable environmental parameters, all of which combine to create a disparity (a skew) in the real arrival time of various signals at their destination. The pre-boot DDR calibration sequence introduces various delays between signals in order to achieve synchronicity. This is where DDR training kicks in; there are a number of patterns (either preset/provided by vendors, or custom-made) that test various signal/delay sets for the best possible ranges of these values. The accuracy of these delays determines the RTL/IOL, and ultimately influences memory performance. Since RTLs and IOLs are set at boot, training has a very real impact on the CAS latency.
Fast Boot settings either skip the memory training entirely, or use a very rough-and-ready form of training. While this is good enough for normal purposes, the best possible training sequence (determined from literature, or comparing the RTL/IOL values resulting from using each test, or in the absence of additional data, using the sequence that takes the longest time) should be used when fine-tuning memory parameters or benchmarking, because the variable signal/delay accuracy from a sub-par training regime makes parameter comparison questionable. Still, if enthusiasts are looking for moderate increases in memory performance, this step is generally optional.