--threads=20 initialy honoured, but reverts to lower threads after about 1 minute
**Describe the bug**
--threads=20 initially utilizes all cores (14) and all threads (20) as specified, but after about 1 minute, reverts to only running on the 8 high efficiency cores.

**To Reproduce**
Behaviour exhibits both during normal mining and benchmarking.

**Expected behavior**
With only 8 cores running, hash rate is about 3kH/s.  With all 14 cores running, hash rate is about 5kH/s.  One would like the maximum possible hash rate, hence the issue.

**Required data**
 - Miner start status: see attached, xmrig-6.19.2
 - command line: xmrig.exe -o xmr.2miners.com:2222 -u wallet.rig_id -p x
 - config file: default as downloaded
 - OS: Windows 11 Pro, Version: 22H2, OS Build: 22621.1555, Experience: Windows Feature Experience Pack 1000.22640.1000.0
 - CPU: Intel i9-12900HK

**Additional context**
See attached Task Manager screen cap demonstrating this behaviour.  When --threads=20 is omitted, miner defaults to just the 8 efficiency cores right from the start and hash rate is 3kH/s.

![Screenshot 2023-04-16 19 58 10](https://user-images.githubusercontent.com/55937877/232351208-dba333c4-f9d6-4dd6-8976-9c10365c6bbb.png)

![Screenshot 2023-04-16 19 37 01](https://user-images.githubusercontent.com/55937877/232351211-7a5d4f65-95e4-43b7-bf4a-ecf97c9092a7.png)
