# S4 implementaion in Freebsd



## ra.hakeem (Mar 26, 2019)

Hi,
Below statement i have read from somewhere

"The S4 sleep state is also known as ``Suspend to Disk.'' ACPI S4 implementation is achieved in two ways. The first way is called S4 BIOS: Firmware saves the running state to disk, and the operating system should do the same thing as S2/S3, then issue a suspend request to BIOS via the special port that triggers a system management interrupt. The second way to handle S4 is to have the operating system handle the saving of state to disk. In this scheme, the operating system should preserve all memory contents, device contexts, and the CPU context. FreeBSD includes a crash dump mechanism that we believe can be adapted for use when implementing OS-initiated S4 sleep. "
But here I want help regarding in second way implementation  for below point
"FreeBSD includes a crash dump mechanism that we believe can be adapted for use when implementing OS-initiated S4 sleep. "
If anybody know about, how could be use *crash dump mechanism* in implementation...kindly let me know 

Regards,


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