diff --git a/sdk/lib/ucrt/vcruntime/isa_available.cpp b/sdk/lib/ucrt/vcruntime/isa_available.cpp
new file mode 100644
index 00000000000..f2806f29084
--- /dev/null
+++ b/sdk/lib/ucrt/vcruntime/isa_available.cpp
@@ -0,0 +1,65 @@
+//
+// isa_available.c
+//
+//      Copyright (c) 2024 Timo Kreuzer
+//
+// Implementation of __isa_available_init.
+//
+// SPDX-License-Identifier: MIT
+//
+
+#include <isa_availability.h>
+#include <intrin.h>
+#include <windef.h>
+#include <winbase.h>
+
+extern "C" { int __isa_available = 0; }
+
+extern "C"
+int
+__cdecl
+__isa_available_init(void)
+{
+#if defined(_M_IX86) || defined(_M_X64)
+    if (IsProcessorFeaturePresent(PF_AVX512F_INSTRUCTIONS_AVAILABLE))
+    {
+        __isa_available = __ISA_AVAILABLE_AVX512;
+    }
+    else if (IsProcessorFeaturePresent(PF_AVX2_INSTRUCTIONS_AVAILABLE))
+    {
+        __isa_available = __ISA_AVAILABLE_AVX2;
+    }
+    else if (IsProcessorFeaturePresent(PF_AVX_INSTRUCTIONS_AVAILABLE))
+    {
+        __isa_available = __ISA_AVAILABLE_AVX;
+    }
+    else if (IsProcessorFeaturePresent(PF_SSE4_2_INSTRUCTIONS_AVAILABLE))
+    {
+        __isa_available = __ISA_AVAILABLE_SSE42;
+    }
+    else if (IsProcessorFeaturePresent(PF_XMMI64_INSTRUCTIONS_AVAILABLE))
+    {
+        __isa_available = __ISA_AVAILABLE_SSE2;
+    }
+    else
+    {
+        __isa_available = __ISA_AVAILABLE_X86;
+    }
+#elif defined(_M_ARM) || defined(_M_ARM64)
+    // CHECKME: Is this correct?
+    if (IsProcessorFeaturePresent(PF_ARM_V8_INSTRUCTIONS_AVAILABLE))
+    {
+#ifdef _M_ARM64
+        __isa_available = __ISA_AVAILABLE_NEON_ARM64;
+#else
+        __isa_available = __ISA_AVAILABLE_NEON;
+#endif
+    }
+    else
+    {
+        __isa_available = __ISA_AVAILABLE_ARMNT;
+    }
+#endif
+
+    return 0;
+}
diff --git a/sdk/lib/ucrt/vcruntime/vcruntime.cmake b/sdk/lib/ucrt/vcruntime/vcruntime.cmake
index 2c3ab680910..dc610565944 100644
--- a/sdk/lib/ucrt/vcruntime/vcruntime.cmake
+++ b/sdk/lib/ucrt/vcruntime/vcruntime.cmake
@@ -5,6 +5,7 @@ list(APPEND UCRT_VCRUNTIME_SOURCES
     vcruntime/__security_init_cookie.c
     vcruntime/__vcrt_init.c
     vcruntime/initializers.cpp
+    vcruntime/isa_available.cpp
 )
 
 if(${ARCH} STREQUAL "i386")