performance from bad to worse

what I expect is 20-40 fps, with really bad performance in jungles (too many leaf blocks?)

What I get with this snapshot is 2-4 fps, even with NO chunk updates. graphics are set to fast, mipmaps off clouds off, particles minimal.

I believe it was w30 or there abouts I was getting nearly 60fps, so I know this computer , though not a powerhouse, is capable.