Done. The portable version still includes the old cygwin binary and runtime for 32-bit apps, though, so please use the DLL from my previous post in place to benchmark as I decided to wait for your results. If you are wondering why I ditched the 64-bit cygwin binary, it isn't just because I was able to build libtxc_dxtn for 64-bit to begin with, but also it was causing instant exits or hangs with 100% CPU utilization on a hyperthread. And all this with an app that doesn't even actively use the extension. It just detects it to show up in a system information board.