TDP is very useful if you want a quiet PC without water cooling. Under clocking may be required based on case airflow, but you want someone to be making passive CPU coolers for your socket.
Not to mention that every slightly larger air cooler is a "passive cooler". Just don't connect the fan. Or set a fan curve that disables the fan as long as the CPU temperature is sub-62 C. Or 95 C, if you really don't want them to turn on.
As to running a larger air cooler without a fan. That’s heavily dependent on case airflow. High speed case fans really defeat the purpose of a passive cooler.
For something a bit more practical, if you're willing to get creative you can passively cool CPUs while getting fairly high performance too: https://www.youtube.com/watch?v=N-z9PidYH4E
Those are just NH-D15s, completely standard coolers with mounting brackets for pretty much every consumer socket out there.
PS: In terms of sacrificing performance, let’s agree to avoid the absurd. Or as the guidelines put it: Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize. Assume good faith.
>Lots of closely spaced thin fins actually produce less cooling without good airflow.
That is true, however Noctua coolers tend to have a fairly big gap between fins, because they are designed for very low RPM use.
>In terms of sacrificing performance, let’s agree to avoid the absurd.
Not sure why you think it's absurd - the video just shows that there is no real minimum amount of cooling required anymore, at least with Intel CPUs. Obviously you're going to have to sacrifice some performance if you go passive only.
Although I'm not even sure anymore what we're even talking about. All consumer CPUs use the same sockets. All these coolers are available for every modern consumer or "pro-sumer" platform.
Motherboard’s use a small set of different mounting brackets for CPU coolers. But the physical CPU socket depends on several things including the physical size of the chip and thus the amount of surface area you want in contact with the the cooler.
In case you where unaware actually running a CPU at 100C will drastically lower it’s lifespan. You encounter similar issue if there are significant temperature differences across the chip. Which is why packaging includes a metal plate over the CPU even though it reduces cooling. However, this is a real tradeoff which means the contact area must be reasonably close to design spec.
For example, when introduced there was no aftermarket passive cooling available for the AM4 socket.
Really of the 5 considerations “Does it fit the mounting bracket?” is probably the least important. Fitting the motherboard and case are mandatory. Fitting the socket and TDP have a little wiggle room. However, with mounting brackets you can generally get something to work as long as you keep firm contact and it does not wiggle around it’s fine.
TDP would be useful if we standardized how it is measured, and at a whole systems level on standardized representative workloads.
(rambling ahead)
Using an r5-3600 as a placeholder waiting for a 3950X. Was running an i7-4790k since that dropped, and wasn't unhappy with it, but there are things where it gets sluggish with the 4 cores, etc. I have definitely noticed the performance difference. Also jumped to Linux (Pop!_OS) from 2 years of hackintosh. I need to update to kernel 5.3 and update video drivers before swapping the older rx570, with an rx5700xt aftermarket.
Actually being able to order certain parts has been a bit of a pain though.