diff --git a/Makefile b/Makefile
index c04074795..fa210ad72 100644
--- a/Makefile
+++ b/Makefile
@@ -316,8 +316,12 @@ endif
 	-@echo "PNOOPT      = $(LAPACK_FPFLAGS) -O0" >> $(NETLIB_LAPACK_DIR)/make.inc
 ifeq ($(C_COMPILER)$(F_COMPILER)$(USE_OPENMP), CLANGGFORTRAN1)
 	-@echo "LDFLAGS     = $(FFLAGS) $(EXTRALIB) -lomp" >> $(NETLIB_LAPACK_DIR)/make.inc
+else
+ifeq ($(C_COMPILER)$(F_COMPILER)$(USE_OPENMP), CLANGIBM1)
+	-@echo "LDFLAGS     = $(FFLAGS) $(EXTRALIB) -lomp" >> $(NETLIB_LAPACK_DIR)/make.inc
 else
 	-@echo "LDFLAGS     = $(FFLAGS) $(EXTRALIB)" >> $(NETLIB_LAPACK_DIR)/make.inc
+endif
 endif
 	-@echo "CC          = $(CC)" >> $(NETLIB_LAPACK_DIR)/make.inc
 	-@echo "override CFLAGS      = $(LAPACK_CFLAGS)" >> $(NETLIB_LAPACK_DIR)/make.inc
diff --git a/Makefile.system b/Makefile.system
index cb5453cac..449069316 100644
--- a/Makefile.system
+++ b/Makefile.system
@@ -1181,7 +1181,7 @@ ifeq ($(F_COMPILER), IBM)
 CCOMMON_OPT += -DF_INTERFACE_IBM
 FEXTRALIB += -lxlf90
 ifeq ($(C_COMPILER), $(filter $(C_COMPILER),GCC CLANG))
-FCOMMON_OPT += -qextname
+FCOMMON_OPT += -qextname -qzerosize
 endif
 # FCOMMON_OPT	+= -qarch=440
 ifdef BINARY64
diff --git a/getarch.c b/getarch.c
index 2b5459a5f..436dc0990 100644
--- a/getarch.c
+++ b/getarch.c
@@ -2006,8 +2006,13 @@ printf("ELF_VERSION=2\n");
   #endif
 #elif NO_PARALLEL_MAKE==1
     printf("MAKEFLAGS += -j 1\n");
+#else
+#ifdef _AIX
+    int count = get_num_cores();
+    printf("MAKEFLAGS += -j %d\n", (count > 32) ? 32 : count);
 #else
     printf("MAKEFLAGS += -j %d\n", get_num_cores());
+#endif
 #endif
 
     break;