diff -rupN eigen-3.4.0/Eigen/src/Core/arch/AltiVec/MatrixProduct.h eigen-3.4.0-new/Eigen/src/Core/arch/AltiVec/MatrixProduct.h
--- eigen-3.4.0/Eigen/src/Core/arch/AltiVec/MatrixProduct.h	2021-08-18 22:41:58.000000000 +0200
+++ eigen-3.4.0-new/Eigen/src/Core/arch/AltiVec/MatrixProduct.h	2021-08-22 17:37:23.626427133 +0200
@@ -28,6 +28,9 @@
 #endif
 #endif
 
+#define EIGEN_ALTIVEC_DISABLE_MMA
+
+
 #ifdef __has_builtin
 #if __has_builtin(__builtin_mma_assemble_acc)
   #define ALTIVEC_MMA_SUPPORT
diff -rupN eigen-3.4.0/Eigen/src/Core/util/Macros.h eigen-3.4.0-new/Eigen/src/Core/util/Macros.h