The mobile GPU (graphics processor unit) market is a tough one. The main GPU cores in the space – Imagination’s PowerVR, ARM’s Mali and Qualcomm’s Adreno – are suffering from the slowdown in smartphone growth just like other components. There are significant new opportunities for firms which can set the pace in emerging GPU technologies, especially those that will power new graphically intense user experiences based around virtual reality. But that requires significant R&D investment, so many players, even the high end groundbreaker Nvidia, will face a difficult hiatus between the old and new growth engines. Imagination Technologies is showing the strain. Its CEO, Sir Hossein Yassaie, who has run the company since 1998, has stepped down as the IP…