12th Generation Intel® Core™ Processors Datasheet, Volume 1 of 2
During S0 idle state, system memory may be conditionally placed into self-refresh state when the processor is in package C3 or deeper power state. Refer to Intel® Rapid Memory Power Management (Intel® RMPM) for more details on conditional self-refresh with Intel HD Graphics enabled.
When entering the S3 – Suspend-to-RAM (STR) state or S0 conditional self-refresh, the processor IA core flushes pending cycles and then enters SDRAM ranks that are not used by the processor graphics into self-refresh. The CKE signals remain LOW so the SDRAM devices perform self-refresh.
The target behavior is to enter self-refresh for package C3 or deeper power states as long as there are no memory requests to service.