After upgrading from 2.63a to 2.64a, my Cycles tile rendering behavior is strange and decidedly less usable. I normally render with 8x8 tiles, and previously a tile would be rendered once for each sample. Now, only the first 9 tiles will render. (This means the middle four, and then the 5 tiles to the left and below.) Once they have completed all passes, the remaining tiles are rendered.
This isn't great since I'll often do a quick preview and cancel the render as soon as there's enough quality to see what's going on. Now, I have to wait for some parts to complete rendering all samples first. The only way around it that I've found so far is to limit tiles to 3x3--which is perhaps not the most efficient setup, although I haven't run benchmarks to determine this. I assume the default is 8x8 tiles for a reason.
I searched a bit but couldn't find any information about this issue. Does anyone know the cause, or how it can be addressed? Thanks.