How do I utilise all the cores for nmake?

According to MSDN, there's no such option for nmake.

You can however make the compiler build multiple files in parallel by using the /MP option with the VC++ command line compiler and passing multiple files at the same time:

> cl /MP a.cpp b.cpp c.cpp

However note that most Makefiles don't call the compiler like this - they usual invoke the compiler separate for each individual source file, which would prevent the /MP option from doing anything useful.

Another generic, non-Qt-related way to tell nmake to use all the cores is to set environmental variable CL to /MP:

set CL=/MP
nmake

will use all the CPU cores.

QT has a tool for this: http://download.qt.io/official_releases/jom/

They also use it per default in Qt creator.