Windows 11 after July 25 update - pegging performance cores, keeping fans running

I have updated Parallels to 20.4.1 and have VMs running Windows 11 24H2 Enterprise with the July update. The issue still happens to me. Support closed my ticket. I'm hoping the engineering team will sort this out because for now I'm having to use actual Windows laptops, which are slightly more reliable than my VMs currently. I can't have the thing just freeze when I'm in the middle of writing code. I'll give the August update a go...
 
That is frustrating if you're still seeing it while on 24H2. This is the first indication of that on this board; all other feedback is that 24H2 makes the problem disappear.
 
PaulWoodward said:
I have updated Parallels to 20.4.1 and have VMs running Windows 11 24H2 Enterprise with the July update. The issue still happens to me. Support closed my ticket. I'm hoping the engineering team will sort this out because for now I'm having to use actual Windows laptops, which are slightly more reliable than my VMs currently. I can't have the thing just freeze when I'm in the middle of writing code. I'll give the August update a go...
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Same with me, its a shame what they are doing blaming windows update for this bug, its completed unsable for me.
 
RandomParallelsUser said:
That is frustrating if you're still seeing it while on 24H2. This is the first indication of that on this board; all other feedback is that 24H2 makes the problem disappear.
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Yeah. I've only been running 24H2 Enterprise VMs since I got this Macbook. These are corporate VMs, and we have standards and compliance requirements. Suggesting rolling back Windows Updates is no good to me, I can't run vulnerable software in Production. I've tried it anyway just to help out the engineers and support team, but frankly Parallels need to be testing the stability of the latest supported versions of Windows 11 as a matter of course, and it doesn't feel like this is happening. It seems the default Windows 11 build on Parallels is still 23H2, but it's 2025, so why would that be?
 
PaulWoodward said:
Yeah. I've only been running 24H2 Enterprise VMs since I got this Macbook. These are corporate VMs, and we have standards and compliance requirements. Suggesting rolling back Windows Updates is no good to me, I can't run vulnerable software in Production. I've tried it anyway just to help out the engineers and support team, but frankly Parallels need to be testing the stability of the latest supported versions of Windows 11 as a matter of course, and it doesn't feel like this is happening. It seems the default Windows 11 build on Parallels is still 23H2, but it's 2025, so why would that be?
Click to expand...

Downgrading Parallels version fixed for me, it worth giving a try.
 
Just updated to Parallels 26, and it just might be resolved. Time will tell, I have note been brave enough to use the machines for actual work that I might lose, but just faffing about and running some benchmarks it's all been OK so far. Here's hoping!
 
Just wanted to update everyone with this issue. I have been experiencing it as well and oddly wasnt noticing the performance hit as much as the battery drain. I am running parallels 26.0.0 and Windows 11 Pro 23H2. I have been experincing this issue for at least a month or two with no resolution. around 50-60% CPU utilization in windows with no apps running or minimized to tray on startup.

I just installed the 2025-08 cumulative update preview (KB5064080) and the issue has finally reslved itself! My issue was not fixed by just updating parallels to 26. It was this windows update in particular. I currently have outlook, slack, a vm viewer (mremote) and chrome with 21 tabs open. Idling at 5% CPU in windows task manager with 7.4GB of ram utilization (of the 12GB I have allocated for Win 11. I'm running on a 2021 M1 Max 32GB. My overall utilization reported on the mac side is idling at 15% CPU and 30% GPU (running 2 external monitors plus macbook display)
 
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