The details, and where the simple version needs a caveat:
- It's called memory training. On the first boot after new RAM (and after a BIOS update or a CMOS reset), the board tests and adjusts the timing and voltage of every data line, then saves the result so later boots are quick.
- "128 wires": with two DDR5 sticks in dual channel, the processor talks to the RAM over 128 data lines (64 per stick), plus extra lines that carry the timing.
- "A sixth of a billionth of a second": at DDR5-6000, each bit gets about 0.17 nanoseconds on the wire.
- How long is normal: one board maker's own table lists about 100 seconds for two 16 GB DDR5 sticks; it can run several minutes with more or bigger sticks. Older DDR4 PCs usually train much faster.
- ⚠️ When it is a fault: if it's still black after roughly ten minutes, or it restarts over and over, try one stick in the slot the manual recommends, update the BIOS, and check the motherboard's DRAM light (it stays lit while training).
- Many boards have a "Memory Context Restore" option that reuses the saved training so later boots skip most of it.
3D model: "Random access memory (RAM) DDR3" by CommunicationNode on Sketchfab, CC BY 4.0.
How long did your first boot take after new RAM?
2026-11-07 00:15