ACPI S3

ACPI S3

• Suspend to RAM
• Requires non volatile DRAM training
• Draws ~1 Watt as DRAM remains powered
• Fast wake up, as everything is already in DRAM

ACPI S3 - Shutdown

• OS writes WakeUp vector to ACPI table
• Sets DRAM into "self refresh" mode
• Tells southbridge to power off and go into S3

ACPI S3 - WakeUp

• 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