ENCX64.DLL is a 64 bit version of ENCX. It can only be installed on 64 bit operating systems. It is for customers who need to release a 64 bit version of their software (normally to take advantages of the extra address space available when processing large amounts of information).
Customers who do not require 64 bit builds at this time can carry on as before.
The installer ENCX64_Setup.msi installs the 64 bit version of the main SDK - ENCX64.DLL. It also installs the 32 bit ENCXCOM.DLL, the chart management applications and samples (all of which remain 32 bit).
Both the 32 and 64 bit installers install files into a Redist folder. On 64 bit operating systems this will be at C:\Program Files (x86)\ENCX SDK\Redist. In contains ENCX.MSM and ENCX64.MSM. These are merge modules that can be incorporated into the installer for your application.
As before if you intend to target only the 32 bit ENCX SDK in .NET builds you should build for 'x86' rather than 'Any CPU'.
If you build for 'Any CPU' your installer must install the correct version of ENCX so that it works on both 32 and 64 bit operating systems.