MSAA only works on separate rendertargets

Hi, I have been trying to get MSAA on the backbuffer to work with no success.

Here is my init code:
public GLGame()
Content.RootDirectory = “Content”;
IsMouseVisible = true;

		_graphics = new GraphicsDeviceManager(this)
			PreferMultiSampling = true,
			GraphicsProfile = GraphicsProfile.HiDef,
			PreferredDepthStencilFormat = DepthFormat.Depth24,
			PreferredBackBufferFormat = SurfaceFormat.Color

I also tried rendering to my own backbuffer, which AA DOES work on:
_backbuffer = new RenderTarget2D(GraphicsDevice, 1800, 1100, false, SurfaceFormat.Color, DepthFormat.Depth24, 8, RenderTargetUsage.PreserveContents);

I’m on DesktopGL. Is there something I’m missing? I’ve also tried attaching to PreparingDeviceSettings and setting the preferred multisample count there, but edges are still jagged.

maybe you are on to something there… i though it was broken for GL only, and had to set the mutlisample count to 1 now i see it does work in GL, but in DX, but if i set back to render target null i get an exception. mabye need to reset the graphics device which would be unfortunate.