OCC has published a new review on the Sparkle Calibre P980X+

Overclocking the card was more complicated than expected. The card artifacted at its factory overclocked speeds, and would begin artifacting at reference clocks as well. Thus the difficulty in overclocking - setting the speeds themselves was easy with Rivatuner and SPAtune. Temperatures were around 55C idle and 75C load, so I dismantled the card and replaced the stock thermal paste with some high performance paste. As a safeguard, while the heat sink was off, I also applied more paste to the heat pipe assembly, coating the pipes in a stickier paste to ensure that there would be good thermal contact. The pipes had little paste, and it seemed somewhat grainy, where the paste replacing it was similar to toothpaste. Once the card was refreshed with two thermal pastes, idle and load temperatures dropped 10C to 15C and the card ran stable at reference speeds. The factory default would still artifact although not as quickly or vigorously, and was caused by the high shader clock speed. The core didn't have much room left in it, a mere 38MHz over the factory tune, while the memory ran up to 1346MHz - a 185MHz overclock! Overall a 5% overclock on the core, 16% on memory, and technically -2.6% on the shader clock speed. Not great, but not bad either - at least the card was pre-overclocked and the memory had some room.

Sparkle Calibre P980X+ Review