I've been trying hard to get my Crucial m500 SSD hard drive to work in edrive (hardware encryption) mode with the w520.
Here's what I've tried so far:
Clean install of Windows 8.1, while running the latest bios 1.42.
All updates from Windows Update tool
All updates from Lenovo System Update EXCEPT the "Intel Rapid Storage AHCI Driver". This seems to be a major point in other threads since apparently the Intel driver is incompatible. I confirm that I'm running Microsoft's "Standard SATA AHCI Controller".
When I enable bitlocker encryption, I'm given the choice to either do the existing data only or the whole drive. According to Crucial tech support, that's a telltale sign that edrive is not being used. As further confirmation, I've also run checked edrive status using this method:
Start Command Prompt as Administrator
Check "Encryption Method" line. It will read "Hardware Encryption" if edrive is in use. Mine says "AES 128"
W520 BIOS doesn't support eDrive. At the time W520 was developed this protocol (and UEFI 2.3.1) didn't exist yet. There isn't any plan to retrofit the older systems to add this support now.
The computer must be UEFI 2.3.1 based and have the EFI_STORAGE_SECURITY_COMMAND_PROTOCOL defined. (This protocol is used to allow programs running in the EFI boot services environment to send security protocol commands to the drive), and the W520 cannot do this.
The computer must have the Compatibility Support Module (CSM) disabled in UEFI.