diff --git a/sources/testing/benchmarks/write-100mb/README.rst b/sources/testing/benchmarks/write-100mb/README.rst
new file mode 100644
index 000000000..ff4e2debf
--- /dev/null
+++ b/sources/testing/benchmarks/write-100mb/README.rst
@@ -0,0 +1,14 @@
+Write 10_000MB, best of three runs on an Apple M3 Pro, May 2024:
+
+       Python  SBCL     Dylan    Racket
+real   7.500s  13.837s  23.425s  30.620s
+       1.0x     1.8x     3.1x     4.1x
+user   4.837s  11.334s   6.455s  21.053s
+       1.0x     2.3x     1.3x     4.4x
+sys    2.286s   2.368s  10.749s   7.031s
+
+
+Note that the other implementations are using Unicode so comparison isn't
+really fair. In particular, Racket does better than SBCL if the test is changed
+to use a byte string (#"xxx") but has a particularly pessimized Unicode path,
+it seems.
diff --git a/sources/testing/benchmarks/write-100mb/write-100mb.dylan b/sources/testing/benchmarks/write-100mb/write-100mb.dylan
index 6982931c0..fc211f580 100644
--- a/sources/testing/benchmarks/write-100mb/write-100mb.dylan
+++ b/sources/testing/benchmarks/write-100mb/write-100mb.dylan
@@ -3,9 +3,12 @@ Module: write-100mb
 define function main
     ()
   let string = make(<string>, size: 100, fill: 'x');
-  with-open-file (stream = "/tmp/100mb.dylan.txt", direction: #"output")
-    for (i from 1 to 1024 * 1024)
-      write(stream, string);
+  for (o from 1 to 100)
+    with-open-file (stream = "/tmp/100mb.dylan.txt",
+                    direction: #"output")
+      for (i from 1 to 1024 * 1024)
+        write(stream, string);
+      end;
     end;
   end;
 end function;
diff --git a/sources/testing/benchmarks/write-100mb/write-100mb.lisp b/sources/testing/benchmarks/write-100mb/write-100mb.lisp
index 1cea66a04..143adaecd 100644
--- a/sources/testing/benchmarks/write-100mb/write-100mb.lisp
+++ b/sources/testing/benchmarks/write-100mb/write-100mb.lisp
@@ -1,9 +1,11 @@
 (in-package :cl-user)
 
-(defun write-100mb ()
+(defun write-10000mb ()
+  ;; (declare (optimize (speed 3) (debug 0)))
   (let ((string (make-string 100 :initial-element #\x)))
-    (with-open-file (stream "/tmp/100mb.sbcl.txt" :direction :output :if-exists :supersede)
-      (loop repeat (* 1024 1024)
-         do (write-string string stream)))))
+    (loop repeat 100
+          do (with-open-file (stream "/tmp/100mb.sbcl.txt" :direction :output :if-exists :supersede)
+               (loop repeat (* 1024 1024)
+                     do (write-string string stream))))))
 
-(write-100mb)
+;;; sbcl --noinform --no-sysinit --no-userinit --eval '(load "write-100mb.lisp")' --eval '(sb-ext:save-lisp-and-die #P"/tmp/clwrite100mb" :executable t :toplevel 'cl-user::write-10000mb)'
diff --git a/sources/testing/benchmarks/write-100mb/write-100mb.rkt b/sources/testing/benchmarks/write-100mb/write-100mb.rkt
new file mode 100644
index 000000000..d638de7d4
--- /dev/null
+++ b/sources/testing/benchmarks/write-100mb/write-100mb.rkt
@@ -0,0 +1,20 @@
+#lang racket/base
+
+(require racket/port)
+
+(define (write-10000mb)
+  ;; Use #"xxx" to write a byte string instead. MUCH faster.
+  (let ((string "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"))
+    (let outer ((o 100))
+      (when (> o 0)
+        (call-with-output-file
+          #:exists 'truncate
+          "/tmp/100mb.racket.txt"
+          (lambda (port)
+            (let loop ((n (* 1024 1024)))
+              (when (> n 0)
+                (display string port)
+                (loop (- n 1))))))
+        (outer (- o 1))))))
+
+(write-10000mb)
diff --git a/sources/testing/benchmarks/write-100mb/write_100mb.py b/sources/testing/benchmarks/write-100mb/write_100mb.py
index 699973191..76c95fb36 100755
--- a/sources/testing/benchmarks/write-100mb/write_100mb.py
+++ b/sources/testing/benchmarks/write-100mb/write_100mb.py
@@ -2,9 +2,10 @@
 
 def main ():
     s = "x" * 100
-    with open("/tmp/100mb.python.txt", "w") as fd:
-        for i in range(1024 * 1024):
-            fd.write(s)
+    for x in range(100):
+        with open("/tmp/100mb.python.txt", "w") as fd:
+            for i in range(1024 * 1024):
+                fd.write(s)
 
 if __name__ == "__main__":
     main()