Since the 1.6.7 update, Picodrive has suddenly become slow and apparently GPU intensive.
I am using a GPD XD with legacy rom and even Master System games are slow and laggy and my device heats up to almost unbearable temperatures within minutes. If I open the menu while using Picodrive, that too is slow and unresponsive.
It was perfectly fine before this update so I am assuming that the latest fixes are the root of the issue.