Switching to the x64 can improve the performance as long as your image still fits in your computer his memory. Your performance will degrade dramatically once disk cache has to be used. With the x86 version this will happen with an image uses more than 2gb of memory. Your convert.exe is probably build without HDRI enabled which cuts the amount of memory in half. And with a Q8 non HDRI version you will even use half of that. The current Q8 build of Magick.NET also has HDRI enabled but maybe I should disable HDRI for that build. Instead of 16 bytes per pixel it will then only use 4 bytes. But then your channel will only have a range of 0-255. Would that be enough for you?
Setting gcAllowVeryLargeObjects will not help because the ImageMagick code is unmanaged.
Setting gcAllowVeryLargeObjects will not help because the ImageMagick code is unmanaged.