diff --git a/BUILD.bazel b/BUILD.bazel
index ea1c7ba..6a01db4 100644
--- a/BUILD.bazel
+++ b/BUILD.bazel
@@ -19,6 +19,15 @@ filegroup(
     visibility = [":__subpackages__"],
 )
 
+filegroup(
+    name = "io-sram-bottom",
+    srcs = [
+        "io-sram-bottom.tcl",
+        ":util",
+    ],
+    visibility = [":__subpackages__"],
+)
+
 filegroup(
     name = "io-boomtile",
     srcs = [
@@ -772,7 +781,7 @@ boom_regfile_rams = [
 [build_openroad(
         docker_image = orfs_version,
         name = ram,
-        io_constraints=":io-sram",
+        io_constraints={'regfile_128x64':":io-sram-bottom", }.get(ram, ":io-sram"),
         verilog_files=["mock/" + ram + ".sv"],
         sdc_constraints = ":constraints-sram",
         stage_args={
diff --git a/io-sram-bottom.tcl b/io-sram-bottom.tcl
new file mode 100644
index 0000000..3dd0f88
--- /dev/null
+++ b/io-sram-bottom.tcl
@@ -0,0 +1,3 @@
+source util.tcl
+
+set_io_pin_constraint -region bottom:* -pin_names [match_pins {(R|W)[0-9]+_.*}]