Hi Pete, welcome to the forum.
Some questions/comments:
[list]
[]What refresh rate are you using? I presume your GUI runs a timerCallback and draws the most recent data? If not, triggering a draw each time processBlock is called would be overkill (unless you’re using blocksizes bigger than 2048)[/]
[]Are you using Visual Studio and launching your program from there? (see Vinnie’s post about the Windows heap being slow when a debugger is attached, also see here)[/][/list]
-Andrew