Cordorb
I have not though about this in years but with more cores per CPU on the way you are right.
Air cooling does throw a lot of air around cooling other chips and now a lot of people are going water.
 
I was reading this as a nice review to catch me up 
 
https://www.tweaktown.com/guides/8482/intel-z370-motherboard-buyers-guide/index5.html
 
I always like to see the close up motherboard pictures.

Gawg36

jonkrmr
Z370 & Coffee Lake-S was a knee jerk reaction from Intel to combat AMD Ryzen. You are right, it is really just a re-branded Z270. The VRM design on Z270 is not really up to the loads required for Coffee Lake-S 6 core CPUs as it was designed for 4 core CPU power loads.
I also have a Gigabyte Aorus Gaming 7 board. This board has a small 40mm fan behind the main VRM under the plastic shield on the back of the board that will kick in at I think 90 degree C but you can change that in BIOS on the board. I have mine set to run at full speed all the time and have not seen my VRM temps under load go much past 50 degree C. VRM heat sinks are designed to require air flow over them to be efficient. They usually get this from the heat sink\fan air flow from your CPU cooler. When water cooling your CPU, you do not get this air flow from the CPU over the VRMs.
Z390 boards should have a VRM design suited to 6-8 core CPU power demands (Z470 is the new chip set for AMD CPUs, not Intel).

I may be wrong, but I have a feeling as long as Z370 boards and i7 or i5 8x00 k are around we may hear more about this. Since posting in fact I read that several boards, mid or budget have problems. They may have only 6 or in some cases 4 VRMs without a heatsink. If OCing they are likely to overheat. But folks who buy those boards are most unlikely to OC I guess.
The thing is, that most manufacturers (I believe only Gigabyte are the exception, and only high end board.) include a sensor dedicated to reading VRM. Even then a good board may have 10+2 or similar or more, so I wonder, does that sensor measure just one VRM (plus close surroundings) or does it intelligently average it. I doubt it's averaged, but I really don't know, and would like to.
 
To add to the last point of monitoring, this can't be done by typical home users as a heat sensor or even infrared would be the only way beyond speculation or even touching them! Ooch!!
Ironically this puts the focus on Gigabyte as it's easy to get a reading. But there are increasing rumors of some highend boards which will be OCed throttling. People don't know for sure why
but a few specialist sites have tested this and found the VRMs are reaching max before throttle. That's hot! Temps vary for each Mosfet/VRM. Luckily the gaming seven has some of the best
in the business which cut off at 135c and have a max of 150c! It's easy to check this with a little searching, I did to verify this. It's true. (the 135c I got directly from a query to a gigabyte engineer.).
 
So JONKRMR, I want to thank you so much for your post. I have that board and was worried. Also good to know that the little fan can be set to always on. I will be doing this, and watching carefully
over the first few weeks. Seems with that board most are very good, but some are terrible as the heatsink has little pressure on the heat pads between it and the mosF. I have been advised to tighten
the screws at the back of the board. A total of 6. I did this and to my amazement sure enough NONE of them were snug. At least a another full turn did the trick without using too much pressure.
Really glad I came across that info. It was by chance but I've spent many hours since looking into it.
 
Your VRM temps underload are IMO excellent! Although they are rated to function at full wack beyond 100c, I get uneasy if they go much past 80c. I'll post when I finally finish the build.
Just to confirm, you have had no problems with your gaming 7 right? VRMs or other stuff?
 
Finally I should qualify all this with a frequent refrain. These over temps on some boards are achieved primarily by running Prime 95 small ffts. So even with a moderately uncomfortable heat
after running that for a while in real world gaming etc It should reach no where near that. Seems Prime 95 small ffts stress the power delivery system more than other more generalized bench
and testing programs, which is good. But still, I'll try it once, and monitor frequently for real life stuff (gaming the like.)
 
Interesting and potentially disturbing stuff. A simple transfer of z270 voltage regulation components to an overclocked coffee lake i7 isn't up to it in many cases. But usually when OCing it should be said.
 
P.S. You are right, at default the little fan kicks in at 90c. Finally do you water cool? I have the arctic 240 which has four fans push pull out the box. Also my case is very large 780T with 2 extra fans I added so a
total of 5 case fans. Trying to get one fan to blow directly on the socket, but this case has no side mount.
 
What do you think? I mean if you have any other ideas or stuff to add. You clearly know your stuff having
already set the little fan to full on, probably without hearing about this "new," issue, particularly z370s with an OCed i7 8700k. Thanks!
 
 

Cordorb
I have not though about this in years but with more cores per CPU on the way you are right.
Air cooling does throw a lot of air around cooling other chips and now a lot of people are going water.
 
I was reading this as a nice review to catch me up 
 
https://www.tweaktown.com/guides/8482/intel-z370-motherboard-buyers-guide/index5.html
 
I always like to see the close up motherboard pictures.