You need to control the GPU with software like MSI afterburner or EVGA’s X1.
There are two clocks (core clock, memory clock) and the power level you will want to maintain.
You can set fan speed in manual or auto mode to cool your GPU. If you use auto, you want to adjust the fan curve to keep the fan speed up in your operating temperature range.
The afterburner software displays two digital frequency meters on the upper left side. You want to reduce the power level (unchained from temp level) while mining without dropping the core clock frequency below 1500 or so. It will drop like a rock after that so just the amount that keeps it at 1500 or above is the right spot. A 3070 may have a higher frequency than 1500, just don’t let it drop to say 300 all of a sudden.
You can safely raise the core clock setting to 100, and increase to 125 if possible. Don’t go too much more. It will help keep the freqency up while you lower the power level.
Set the temp level at least 10C higher than the current temp, and use fan speed to keep the card under 60C. Two fan models tend to run around 50+C and 3 fan models can run in the 40+C range.
Start with a memory clock above 100 on the setting and the frequency display will be around 6000-7000. Increase in steps of 100 until the computer freezes. You should easily get a setting of 1000 and frequency of 8000. After that is where the fun starts. Once you narrow down the setting where you trip out the GPU and have to reboot, lower the setting by 100. This should get you a nice stable operatiing point. A high memory clock that doesn’t crash the system may result in Invalid shares. Lower the clock until there are no invalid shares.
The video card freezing up is typically due to too high memory clock. Temperature is related to power level. Even if the card seems stable at higher settings, it may not run 24 hours continuosly on the pool. The elapsed time is displayed on the software. If it quits running, the GPU is not stable or the network is not stable. Lower clocks somewhat.
Finally, Both Phoenix miner and T-rex miner have setting in the batch file that can detect an idled or crashed GPU and will restart the miner (or computer). Adding a shortcut to the computers startup folder will automatically restart the miner if the computer reboots. I’ve done this on my computer and it prevents long periods of not mining as computers reboot for many unknown reasons.
Key to continuous operation is a stable computer.