Previously, the x86 version you are able to debug 32bit worker processes running on 32/64bit OSes, with this release – you can now debug a full 64bit worker processes.
Here’s the link at Microsoft download, and addtional note for x64 release
Notes about the x64 release:
– Installing both x68 an x64 releases on the same x64 OS is not supported.
– To debug x86 processes running on x64 OS, use the x86 release
Note – the DebugDiag download at IIS.net has not refreshed yet, also it is still using ver1.1 which was released years ago.