Add a known issue for missing AVX in CTP 2.1

Author: dimitri-furman

docs/sql-server/sql-server-2025-release-notes.md

@@ -4,7 +4,7 @@ description: Find information about SQL Server 2025 (17.x) limitations, known is
 author: MikeRayMSFT
 ms.author: mikeray
 ms.reviewer: randolphwest
-ms.date: 06/19/2025
+ms.date: 06/26/2025
 ms.service: sql
 ms.subservice: release-landing
 ms.topic: release-notes
@@ -27,13 +27,13 @@ For hardware and software requirements, see [Hardware and software requirements
 
 ## Known issues
 
-### SQL Server on Windows fails to start after installation
+### SQL Server on Windows fails to start on machines with more than 64 logical cores per NUMA node
 
 **Issue**: SQL Server instances on Windows might fail to start after the installation if the machine has more than 64 logical cores per NUMA node.
 
 For more information, see [Limit number of logical cores per NUMA node to 64](compute-capacity-limits-by-edition-of-sql-server.md#limit-number-of-logical-cores-per-numa-node-to-64).
 
-### SQL Server on Linux fails to start after installation
+### SQL Server on Linux fails to start on machines with hybrid CPU architecture
 
 **Issue**: SQL Server instances on Linux might fail to start if the machine uses an Intel 12th Gen or later hybrid architecture CPU, and the host operating system is Linux.
 
@@ -45,6 +45,14 @@ Reason: 0x00000004 Message: ASSERT: Expression=(result * DrtlGetProcessorCoreCou
 
 If you want to use a Linux host operating system, you can work around the issue by disabling efficiency cores (E-cores) in your BIOS. If you use containers, or a hypervisor like Hyper-V on Windows (including WSL), you aren't affected.
 
+### SQL Server fails to start if AVX2 CPU instructions aren't available
+
+**Issue**: In CTP 2.1 (version 2025.170.800.3), SQL Server doesn't start if AVX2 CPU instructions aren't available on the machine.
+
+In the Windows application event log, you see an **Error** event referencing exception code `0xc000001d` and a faulting module path that includes `sqllang.dll`.
+
+To work around this issue, enable AVX2 CPU instructions on the machine. AVX instructions might be disabled in the machine BIOS or UEFI, or disabled in the hypervisor configuration.
+
 ### Upgrade in place
 
 [!INCLUDE [sssql25-md](../includes/sssql25-md.md)] doesn't support in place upgrades from previous versions of [!INCLUDE [ssnoversion-md](../includes/ssnoversion-md.md)], including SQL Server 2025 CTP releases.