Resolved issues in Windows Server 2025
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Resolved issues
| Summary | Originating update | Status | Date resolved |
|---|---|---|---|
| Windows Server 2025 might not run as expected on devices with high core count This is observed on servers with 256 or more logical processors. Issues may not trigger consistently. | N/A | Resolved KB5046617 | 2024-11-12 10:00 PT |
Issue details
October 2024
Windows Server 2025 might not run as expected on devices with high core count
| Status | Originating update | History |
|---|---|---|
| Resolved KB5046617 | N/A | Resolved: 2024-11-12, 10:00 PT Opened: 2024-10-31, 13:11 PT |
Servers which have a high number of logical processors might experience issues running Windows Server 2025. This is presently observed on servers which have 256 or more logical processors.
On these devices, one or more of the following issues might be encountered:
- Windows Server 2025 installation or upgrading processes might fail or stop responding.
- Starting or restarting Server might take an excessive amount of time, such as 3 hours or more.
- An error message on a blue screen appears when starting, restarting, or trying to run an application.
Issues may not trigger consistently, for which it is also possible that the server will start and operate without problem.
To determine whether you are encountering this issue because the number of logical processors on the device exceeds 256, open the Windows Task Manager. This can be accomplished by pressing CTRL+SHIFT+ESC. From there, select the Performance tab and note the number of logical processors reported in the bottom half of the window.
Resolution: This issue was resolved by Windows updates released November 12, 2024 (KB5046617), and later. We recommend you install the latest security update for your device as it contains important improvements and issue resolutions, including this one. If you install an update released November 12, 2024 (KB5046617) or later, you do not need to use a workaround for this issue. If you are using an update released before this date, and have this issue, you have the option to apply the following workaround:
To temporarily prevent this issue, you will need to limit the total number of logical processors on the server to 256 or under. Changing the number of logical processors will vary depending on the firmware installed on your device.
To adjust the number of logical processors, follow these steps:
- Restart your server and enter the UEFI Setup. Navigate through the firmware menus, which may vary by manufacturer.
- Locate any option which allows you to adjust the number of cores per socket.
- Set the number of cores per socket to a value that ensures the total number of logical processors is 256 or fewer. Important: The total number of logical processors is calculated by first multiplying the number of sockets by the number of cores per socket, and then multiplying that result by the number of logical processors per core.
- Restart the server.
Affected platforms:
- Client: None
- Server: Windows Server 2025
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