I am going crazy with my two 3090s. Both run at about 105Mh/s. The MSI Triple is the primary and runs without issues, but the Gigabyte secondary either wants to spin the fans up to 100%, or throttle GPU down to 800Mhz, and crank out only 80MH/s. I have tried power limiting, GPU downclocking, and memory overclocking, however could not resolve the issue. I have a healthy Corsair 1200W power supply which previously ran 4x1070s and a single 1080 with no issues. Power draw shows 350W on the MSI, and 250W on the Gigabyte (on a riser). Both have their PCIE power inputs fully populated with clean power. Any ideas?
You have to have a huge memory downclock with a fan blasting air on the backplate... Also you must make sure that whatever 3090 you are using has memory cooling pads that touch the backplate. The issue is the GDDR6X gets extremely hot and overwhelmed with an overclock passed 500MHz and then the core is downclocked to try and cool it.