system out of memory when trying to saveAsPng

Hi first of I create my rendertarget2D

_canvas = new RenderTarget2D(_device, _canvasSize, _canvasSize);

Then I try and save it

using (FileStream stream = File.Create("texturepack" + _canvasSize.ToString()))
                _canvas.SaveAsPng(stream, _canvasSize, _canvasSize);

at this point the memory jumps up to just over 700mbs then I get System.OutOFMemoryException

What I don’t understand is I have both 8gb of system memory and 8gb of gpu memory
Now the texture is massive 8192x8192 but still I shouldn’t be getting this error when I have over 3 gb of memory free.

Any help would be apricated

EDIT: running windows directX and using HiDef profile

I’m not sure if this will help but have a search for “C# Large address aware”.

I’ve used it in non-gaming related software to applications that were using too much RAM.

It may help you out.

Thank you so much, just had to build for x64 and it worked perfectly.