What I pray in many threads currently is how to deal with Intels TDP because many customers are not happy with their CPU temps.
I recommend to setup "Max Long Power Duration" = 95W or lower in UEFI/Bios. This will let your CPU run in Intel specs and it will be so much cooler. I tested it with an 8700k and an L9i. Here are some results (Prime95 8k):
Auto (125W) = 100+°C /6x 4,3Ghz
95W = 91°C /6x 3,9-4,0Ghz
80W = 80°C /6x 3,7-3,8Ghz
65W = 72°C /6x 3,5-3,6Ghz
100W + undervolt = 87°C / 6x 4,1 -4,2Ghz.
I know you are losing some MHZ IF ALL CORES ARE IN USE but the performance loss is very low (~8% depending on TDP value). Keep in mind these values are for Prime95 in games the temp will be 10°C lower. So with the Alpen Ridge and a 120mm bottom fan you can expect the following temps:
CPU @ TDP 100W + undervolted -0,1V = 6x 4,1 -4,2Ghz.:
Prime95 ~ 78-82°C
Games ~ 68-72°C
If you follow this guide for the 9900k I think it will be also possible to have good temps on this CPU.
UPDATE: On Computerbase.de I found an information about the performance loss on 9900K TDP no limit VS TDP 95W limit. The avarage perfromance loss is 1,2% in games for FPS and 2,9% for frametimes. In applications the avarage performance loss is 8%.
