diff --git a/tool/cosmocc/README.md b/tool/cosmocc/README.md
index 987fb5d3f..39a8f03fe 100644
--- a/tool/cosmocc/README.md
+++ b/tool/cosmocc/README.md
@@ -134,6 +134,13 @@ kinds of codebases using `cosmocc` which is just a convenient wrapper
 around the cross compilers, which would be a better choice to use in
 this type of circumstance.
 
+## Usage
+
+By default, all the code you compile will use the baseline of the X86_64
+and AARCH64, which is K8 and ARMv8.0. You can pass architecture specific
+flags to use newer ISAs by using the `-Xx86_64` and `-Xaarch64` prefixes
+like `-Xx86_64-mssse3` and `-Xaarch64-march=armv8.2-a+dotprod`.
+
 ## Troubleshooting
 
 Your `cosmocc` compiler runs a number commands under the hood. If
diff --git a/tool/cosmocc/bin/cosmocc b/tool/cosmocc/bin/cosmocc
index 2b0196e4b..277214a91 100755
--- a/tool/cosmocc/bin/cosmocc
+++ b/tool/cosmocc/bin/cosmocc
@@ -185,7 +185,7 @@ for x; do
     continue
   elif [ x"$x" != x"${x#-Xaarch64}" ]; then
     x=${x#-Xaarch64}
-    FLAGS_aarch64="$FLAGS_aarch64 $x"
+    FLAGS_AARCH64="$FLAGS_AARCH64 $x"
     continue
   elif [ x"$x" = x"-dumpversion" ]; then
     echo $GCC_VERSION
diff --git a/tool/viz/hwcap.c b/tool/viz/hwcap.c
new file mode 100644
index 000000000..b2123f07a
--- /dev/null
+++ b/tool/viz/hwcap.c
@@ -0,0 +1,85 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8                               :vi │
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2024 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/sysv/consts/hwcap.h"
+#include "libc/runtime/runtime.h"
+#include "libc/stdio/stdio.h"
+#include "libc/sysv/consts/auxv.h"
+
+int main(int argc, char *argv[]) {
+#ifdef __aarch64__
+
+  long x = getauxval(AT_HWCAP);
+
+  if (x & HWCAP_FP) puts("HWCAP_FP");
+  if (x & HWCAP_ASIMD) puts("HWCAP_ASIMD");
+  if (x & HWCAP_EVTSTRM) puts("HWCAP_EVTSTRM");
+  if (x & HWCAP_AES) puts("HWCAP_AES");
+  if (x & HWCAP_PMULL) puts("HWCAP_PMULL");
+  if (x & HWCAP_SHA1) puts("HWCAP_SHA1");
+  if (x & HWCAP_SHA2) puts("HWCAP_SHA2");
+  if (x & HWCAP_CRC32) puts("HWCAP_CRC32");
+  if (x & HWCAP_ATOMICS) puts("HWCAP_ATOMICS");
+  if (x & HWCAP_FPHP) puts("HWCAP_FPHP");
+  if (x & HWCAP_ASIMDHP) puts("HWCAP_ASIMDHP");
+  if (x & HWCAP_CPUID) puts("HWCAP_CPUID");
+  if (x & HWCAP_ASIMDRDM) puts("HWCAP_ASIMDRDM");
+  if (x & HWCAP_JSCVT) puts("HWCAP_JSCVT");
+  if (x & HWCAP_FCMA) puts("HWCAP_FCMA");
+  if (x & HWCAP_LRCPC) puts("HWCAP_LRCPC");
+  if (x & HWCAP_DCPOP) puts("HWCAP_DCPOP");
+  if (x & HWCAP_SHA3) puts("HWCAP_SHA3");
+  if (x & HWCAP_SM3) puts("HWCAP_SM3");
+  if (x & HWCAP_SM4) puts("HWCAP_SM4");
+  if (x & HWCAP_ASIMDDP) puts("HWCAP_ASIMDDP");
+  if (x & HWCAP_SHA512) puts("HWCAP_SHA512");
+  if (x & HWCAP_SVE) puts("HWCAP_SVE");
+  if (x & HWCAP_ASIMDFHM) puts("HWCAP_ASIMDFHM");
+  if (x & HWCAP_DIT) puts("HWCAP_DIT");
+  if (x & HWCAP_USCAT) puts("HWCAP_USCAT");
+  if (x & HWCAP_ILRCPC) puts("HWCAP_ILRCPC");
+  if (x & HWCAP_FLAGM) puts("HWCAP_FLAGM");
+  if (x & HWCAP_SSBS) puts("HWCAP_SSBS");
+  if (x & HWCAP_SB) puts("HWCAP_SB");
+  if (x & HWCAP_PACA) puts("HWCAP_PACA");
+  if (x & HWCAP_PACG) puts("HWCAP_PACG");
+
+  x = getauxval(AT_HWCAP2);
+
+  if (x & HWCAP2_DCPODP) puts("HWCAP2_DCPODP");
+  if (x & HWCAP2_SVE2) puts("HWCAP2_SVE2");
+  if (x & HWCAP2_SVEAES) puts("HWCAP2_SVEAES");
+  if (x & HWCAP2_SVEPMULL) puts("HWCAP2_SVEPMULL");
+  if (x & HWCAP2_SVEBITPERM) puts("HWCAP2_SVEBITPERM");
+  if (x & HWCAP2_SVESHA3) puts("HWCAP2_SVESHA3");
+  if (x & HWCAP2_SVESM4) puts("HWCAP2_SVESM4");
+  if (x & HWCAP2_FLAGM2) puts("HWCAP2_FLAGM2");
+  if (x & HWCAP2_FRINT) puts("HWCAP2_FRINT");
+  if (x & HWCAP2_SVEI8MM) puts("HWCAP2_SVEI8MM");
+  if (x & HWCAP2_SVEF32MM) puts("HWCAP2_SVEF32MM");
+  if (x & HWCAP2_SVEF64MM) puts("HWCAP2_SVEF64MM");
+  if (x & HWCAP2_SVEBF16) puts("HWCAP2_SVEBF16");
+  if (x & HWCAP2_I8MM) puts("HWCAP2_I8MM");
+  if (x & HWCAP2_BF16) puts("HWCAP2_BF16");
+  if (x & HWCAP2_DGH) puts("HWCAP2_DGH");
+  if (x & HWCAP2_RNG) puts("HWCAP2_RNG");
+  if (x & HWCAP2_BTI) puts("HWCAP2_BTI");
+  if (x & HWCAP2_MTE) puts("HWCAP2_MTE");
+
+#endif /* __aarch64__ */
+}