In their core dynamic clock speeds for CPUs are simple enough. There is a base clock that CPU is essentially guaranteed to hit with any load, all cores being loaded being the main thing here. Then there is maximum boost clock which is for one core load only.
Both these clocks are published by both Intel and AMD. I will use lower range models for examples as the ranges are wider there:
Ryzen 7 1700 has base clock of 3.0GHz and Precision Boost of 3.7GHz. In reality, 1700s will generally run at 3.2GHz with all-core load.
i7 7700 has base clock of 3.6GHz and Max Turbo 4.2GHz. Intel has also published the
frequency table for it showing that Max Boost for 1 core load is 4.2GHz, for 2 core load 4.1GHz and for 4 core load 4.0GHz.
However, there are a number of 'but'-s in there.
- Base clock is worst case scenario, in Intel's case that actually means including full AVX load (with offset). I am not sure what base clock means for AMD.
- Max Boost and Precision Boost clocks are not the end of things either. Intel has (or had as they seem to have hidden or discontinued it and it required software support) Boost 3.0 boost that was 100mhz higher. AMD has XFR (+50/100MHz) that requires X370 motherboard and is opportunistic.
- As you can see from above both Intel and AMD CPUs actually boost higher than base clock with all cores being loaded.
- There are variables in place that will drag down clock speeds and throttle the processor. Most notably, temperature and TDP.
None of this will change. Intel just feels they no longer want to publish the table of potential maximum clock speeds for each number of loaded cores. It is worth noting that AMD does not publish this information either and based on what is publicly available, Turbo Core is more simple around how clocks are determined.
The main reason for not wanting that table published is probably liability as has been mentioned a bunch of times in this thread. When they publish it, customers may feel (justified or not) these clocks are guaranteed when these are just the baseline for determining the current viable clock speed.
There are also technical changes in recent Intel processor families that may have contributed to the decision. AVX/AVX2 is already wreaking havoc in Intel processors when it comes to clock speeds, power consumption and temperatures. Now they are adding AVX-512 starting with HPDT. Intel also seems to be pushing the 1-2-4 core load across the board higher than ever before. Almost across the entire range of last generations the Max Boost is 4.x GHz with very few exceptions. over 4GHz from 4 cores to 18 cores is a wide range. Trying to manage that in given limitations must be hell and that is pushing the frequency ranges to be very wide. This is mostly done with tweaking the Turbo Boost rather than other technical changes. Why they are doing everything to achieve that is probably thanks to Ryzen. If they let low-threaded clocks slip, the gaming edge of Intel's CPUs is lost.
Coffee Lake is in its core still the same Skylake/Kaby Lake and 14++nm process is just a minor improvement.
Take a look at the prime suspect for Intel being malevolent (i5 8400) and compare it to its direct predecessor (i5 7400):
https://ark.intel.com/compare/126687,97147
- Now 6 cores need to be fit in the same 65W TDP. That logically means something has to give - and that something is base clock speed that decreased by 200MHz (which is not a bad result from technical perspective).
- The other end is trying to boost the low-core boost clock as I mentioned in previous paragraph. Single core at 4.0GHz is 500Mhz higher than i5 7400 which will no doubt have serious positive effect on single-core perf level.
I do not see any of this as particularly suspicious.