- Suspend to RAM
- Requires non volatile DRAM training
- Draws ~1 Watt as DRAM remains powered
- Fast wake up, as everything is already in DRAM
- OS writes WakeUp vector to ACPI table
- Sets DRAM into "self refresh" mode
- Tells southbridge to power off and go into S3
- Firmware finds the S3 sleep state was active
- In romstage:
- Skips DRAM training
- Applies trained DRAM timings from MRC cache
- Non intrusive memory test
- In ramstage:
- Skips video init
- Skips ACPI/SMBIOS table generation
- Skips loading a payload
- Jumps to ACPI WakeUp address