Thank you both for your quick replies. Unfortunately I think I am doing it as you suggest. I am running using OpenGL 4.2. So for example if I have a large number of vertices for a triangle strip, all...

Yes, that is correct. I re-read the OpenGL spec, and it suggests that that is exactly how should work. And it does on NVIDIA.

In programs I write using strictly forward compatible, core profiles (and typically 4.2), I have noticed that per-vertex attributes specified using glVertexAttrib* seem to be ignored on devices with...

I have been doing OpenGL for many years now, and I am in the market to buy a new high-end linux laptop, largely for OpenGL work. (I'm done putting up with Apple's lack of support for modern OpenGL.)...