diff --git a/buildflags.md b/buildflags.md
index 8d2dd1d..58a27ad 100644
--- a/buildflags.md
+++ b/buildflags.md
@@ -438,14 +438,15 @@ tuning in the `gcc` package.  These settings are:
     point math to avoid excess precision issues.  `-mstackrealign`
     avoids relying on the stack alignment guaranteed by the current
     version of the i386 ABI.
-*   **ppc64le**: `-mcpu=power8 -mtune=power8` selects a minimum supported
-    CPU level of POWER8 (the first CPU with ppc64le support) and tunes
-    for POWER8.
-*   **s390x**: `-march=zEC12 -mtune=z13` specifies a minimum supported CPU
-    level of zEC12, while optimizing for a subsequent CPU generation
-    (z13).
-*   **x86_64**: `-mtune=generic` selects tuning which is expected to
-     beneficial for a broad range of current CPUs.
+*   **ppc64le**: `-mcpu=power9 -mtune=power9` selects a minimum supported
+    CPU level of POWER9.
+*   **s390x**: `-march=z14 -mtune=z15` specifies a minimum supported CPU
+    level of z14, while optimizing for a subsequent CPU generation
+    (z15).
+*   **x86_64**: `-march=x86-64-v2 -mtune=generic` builds for the
+    [x86-64-v2 micro-architecture level](https://gitlab.com/x86-psABIs/x86-64-ABI/-/blob/master/x86-64-ABI/low-level-sys-info.tex)
+    and selects tuning which is expected to beneficial for a broad range
+    of current CPUs.
 *   **aarch64** does not have any architecture-specific tuning.
 
 # Individual linker flags