Adding a 2nd Nvidia GPU - any head's up?

[MeeLee]

I would disagree with that.
Have you ever seen those 2,5 to 3 slot GPU coolers they put on GPUs nowadays?
They're well suited for 200-250W GPUs, while beefy CPU coolers are usually rated to 180-200W CPUs.
The total surface area of a GPU cooler (RTX type with 2 or 3 fans) is much larger than even a beefy CPU cooler.

My 2080Tis run at 100% fan, and between 1750Mhz to 2100Mhz on average. Most of the time they're running around the 1875Mhz range.
They are overclocked by 100-120Mhz, and power capped to 200-215W.

There are single or dual slot heat sinks, with single or dual fans built in, that won't effectively cool any GPU.
But as long as you get at least a dual fan design for 2070 or less, and a triple fan design for 2080, 2080Super, and 2080Ti you should still see cool (sub 60C) temperatures.

Watercooling has gone a long way, the earlier models were actually worse than current open air systems.
But they're not THAT much better than air, especially not for the price premium you pay for them.

[HaloJones]

I would disagree with that.

Watercooling has gone a long way, the earlier models were actually worse than current open air systems.
But they're not THAT much better than air, especially not for the price premium you pay for them.

You're still comparing to AIO's.

But FWIW, I have a GTX1070. Its original Founders Edition air cooler let the gpu run at 80C and 1960MHz as per the factory BIOS so typically the fans were pretty quiet.

I took that off, fitted a NZXT G10 bracket and a 280mm AIO to cool that 1070. With two slow 140mm fans on the radiator that 1070 now clocks at 2075 and stays below 40C. That means it will last longer (hopefully).

[kiore]

I have 3x 2080Tis each running at below 60C. On Core 21 they would run in the lower 50's (depending on ambient sometimes in the higher 40s).

Like I said, unless you're working with a constricted space, air coolers work just as well as those water cooling systems you find on GPUs that are at least $500 overpriced compared to open air cooled GPUs.
Many websites (like Linus Tech Tips, Tom's hardware, and a few others) would agree that water cooling and decent air cooling are pretty much the same.
Think about it, a water cooling loop, is essentially also an aircooling circuit.
The radiator gets cooled by a fan, which is... air cooled...

Meelee, OK so your experience and my experience are different. But I think you are wrong when you say that liquid cooled is essentially aircooled although I agree this is how the radiator is cooled the radiator can be distant from the heat source and I think this is the critical factor. Instead of very effective fans moving already hot air around the case I find that moving the radiator away from the heat source causes significant differences in temperature especially when folding with multi GPUs. I previously had a rig which was a test bed with 3 hybrid GPUs on it, I built a frame that staggered the radiators and lifted them well clear of the GPUs venting out a window, there is no way even the best air cooler would have dealt with these cards millimetres apart even on a test bed like this. OK in the distant past I would have 4 x GTX 260s or 9800GTs right up against each other, but those days are long gone.

[MeeLee]

The main issue with open air coolers is that they're essentially only 75% open. Air moves in from the top, and out from the sides.
The bottom is mounted to the GPU chip and board.
Water cooler radiators are over 99% open, air basically goes through them.
That being said, if you can get your GPU running at 60C with air, there's very little performance difference between it, and getting a water cooler down to 40C.
The Nvidia drivers are only upping the frequency by I would estimate about 100Mhz (so instead of 1875-1905Mhz, they might be running at 1975-2005Mhz).