Render TOP 'glitchy' not showing render OSX

Hi,

I’m totally new to TouchDesigner and am following some tutorials to learn about various aspects.

I have set up a 3D scene, with camera, light, geometry COMPs and a render TOP. I can see the geom in all of the the COMPs but I just have artefacts in the render TOP.

I am guessing it’s something to do with my graphics card and version of OSX on my old mac.

I have searched for a solution but I don’t seem to be able to get the right combination of terms to get an answer.

Sorry if this has been covered lots of times before!

Info:
Touchdesign build 2018.27840

OSX 10.11.6 El Capitan
iMac (27-inch, Late 2009)
2.8 GHz Intel Core i7
8 GB 1067 MHz DDR3
ATI Radeon HD 4850 512 MB
Screen Shot 2019-02-13 at 12.40.19.png