A mining rig is a space heater that happens to do math. Run it hard enough for long enough and it will try to destroy itself with its own waste heat. Your job is to move that heat out of the case, out of the room, and out of the building faster than the cards can make it. Do that well and a GPU lasts years. Do it badly and you are shopping for replacement fans in 3 months and a replacement card in 8.
Start with the number that actually matters: memory junction temperature. Core temp is the friendly number the manufacturer likes to show you, and it lies by omission. On cards with GDDR6X, like the RTX 3080 and 3090, the memory sits under the same cooler as the core but runs much hotter, and the memory is what you are hammering when you mine. A card can report a core at 60C while the memory junction is sitting at 104C. Above 110C that memory throttles hard, and living in the high 90s and low 100s for months cooks the thermal pads until they turn to chalk. If your monitoring software shows a memory junction reading, watch that one. Keep it under 100C. Under 90C is where you want to be.
Ambient is the ceiling you can’t beat
Every temperature inside the case is stacked on top of the temperature of the room. If the air going into the rig is 30C, no fan on earth gets your card down to 25C. You are always fighting from ambient upward. This is why the same rig that runs fine in February starts throttling in July. A garage that sits at 22C in winter can hit 38C in a summer afternoon, and that 16 degree swing lands directly on your silicon.
So manage the room before you fiddle with anything on the card. Pull cool air in from the lowest, coolest part of the space and dump hot air out somewhere it won’t recirculate. Hot air rises, so exhaust high and intake low. If you are venting into an attic or a closet, you are just preheating your own intake air, and the whole rig slowly bakes over the course of a day. A cheap thermometer at the intake tells you more than most people’s entire monitoring setup.
Airflow beats fan speed
More static pressure through the case matters more than screaming fans on the cards themselves. A rig in a tight enclosure with three cards jammed together will always run hotter than the same cards on an open frame in the same room, because the middle card is breathing the exhaust of its neighbors. Space the cards out. Open-air mining frames exist for exactly this reason. If you are stuck with an enclosed case, add a box fan or an inline duct fan moving real volume through it, not just the stock case fans.
Fan curves are the next lever. The default curve on most cards is tuned to stay quiet, which means it lets the card get hot before it spins up. For mining you want the opposite: aggressive early, so the card never gets a chance to heat-soak. Set a custom curve that has the fans at 60 to 70 percent by the time the card hits 55C, and near 100 percent by 70C. Yes it is louder. A rig is not a living-room PC. The tradeoff is that the fans and the card both last longer when the card never sits in the danger zone waiting for the fans to catch up.
One caution: running fans at 100 percent 24/7 wears the bearings out. Sleeve-bearing fans in particular start rattling and dying after a year of full-tilt duty. Double ball-bearing fans handle it better. If a fan starts making a grinding or clicking noise, replace it before it seizes, because a dead fan on a loaded card is how you get a thermal shutdown at 3am, or worse, no shutdown and a scorched card.
Dust is a slow strangle
Dust is the killer nobody schedules for. A GPU heatsink is a dense stack of thin fins, and it works by having air pass between them. Dust bridges the gap between fins, and within a couple of months a card in a dusty room loses a noticeable chunk of its cooling capacity. The card compensates by ramping fans and, when that runs out, by thermal throttling down its clocks, which quietly drops your output while you’re not looking.
Blow the rigs out with compressed air every 4 to 6 weeks, more often if you have pets or the rig lives in a garage. Hold the fans still with a finger or a zip tie while you blow, because spinning a fan backward with a jet of air can generate voltage and damage it. Do this outdoors or you are just relocating the dust. A furnace filter taped over the intake side of an open frame catches most of it and is far easier to swap than cleaning fins.
Thermal pads and paste
The pads and paste under the cooler are consumables on a mining card, even though nobody sells them that way. Factory thermal paste dries out under constant load, and the memory pads compress and lose contact. If a card that used to run at 90C memory junction is now sitting at 104C with clean fins and good airflow, the pads are done. Repadding the memory with 1.5mm or 2mm pads and repasting the core can drop junction temps 15 to 20 degrees on a tired card. It is fiddly, it voids the warranty, and it is often the difference between a card that lasts another 2 years and one that dies this summer.
Watch it before it bites you
Heat problems announce themselves early if you are looking. Log memory junction temp, core temp, fan speed, and power draw, and glance at them once a day. A card that used to sit at 88C and now idles the same graph at 96C is telling you something clogged, dried out, or loosened. Most miners run monitoring on the whole rig anyway, so add a temperature alert that pings you when any card crosses 100C junction. That single alert has saved more cards than any fancy cooler.
Set the thermal limits in software too, as a backstop. Cap the card’s power limit and set a temperature target so it throttles itself before it hits shutdown. Throttling costs you a little output for a few minutes. A card that runs full-tilt into a thermal wall with a dead fan costs you the card. Give yourself the soft landing.
Placement matters more than people expect. A rig shoved against a wall, under a desk, or in a cabinet is choking on its own exhaust no matter how good the fans are. Give it 30cm of clear space on the intake and exhaust sides, keep it off carpet that blocks the bottom and sheds fibers into the fans, and point the hot exhaust away from anything you care about. The best cooler in the world cannot fix a rig that is breathing its own hot air.
Keep the memory cool, keep the room cool, keep the fins clean, and stay ahead of the fans. Everything else is detail.