diff --git a/src/main/resources/testchipip/bootrom/bootrom.S b/src/main/resources/testchipip/bootrom/bootrom.S
index be0c3bc8..dc899567 100644
--- a/src/main/resources/testchipip/bootrom/bootrom.S
+++ b/src/main/resources/testchipip/bootrom/bootrom.S
@@ -1,4 +1,4 @@
-#define DRAM_BASE 0x80000000
+#define BOOTADDR_REG 0x4000
 
 // boot all cores (only hart 0) and jump to main program execution
 .section .text.start, "ax", @progbits
@@ -43,13 +43,18 @@ boot_core:
   bnez t0, boot_core // block until hart 0 clears own MSIP
   sll a0, a0, 2      // offset for hart MSIP
   add a1, a0, a1
-boot_core_hart0:   // begin executing code at DRAM_BASE
-  sw zero, 0(a1)   // clear the interrupt
-  li a0, DRAM_BASE // program reset vector
-  csrw mepc, a0    // return from interrupt to start of user program
-  csrr a0, mhartid // hartid for next level bootloader
-  la a1, _dtb      // dtb address for next level bootloader
-  li a2, 0x80      // set mstatus MPIE to 0
+boot_core_hart0:      // begin executing code at DRAM_BASE
+  sw zero, 0(a1)      // clear the interrupt
+  li a0, BOOTADDR_REG // program reset vector
+#if __riscv_xlen == 32
+  lw a0, 0(a0)        // get boot address from bootaddr_reg SCR
+#else
+  ld a0, 0(a0)        // get boot address from bootaddr_reg SCR
+#endif
+  csrw mepc, a0       // return from interrupt to start of user program
+  csrr a0, mhartid    // hartid for next level bootloader
+  la a1, _dtb         // dtb address for next level bootloader
+  li a2, 0x80         // set mstatus MPIE to 0
   csrc mstatus, a2
   mret
 
diff --git a/src/main/resources/testchipip/bootrom/bootrom.rv32.img b/src/main/resources/testchipip/bootrom/bootrom.rv32.img
index 12a9111d..801bdb50 100755
Binary files a/src/main/resources/testchipip/bootrom/bootrom.rv32.img and b/src/main/resources/testchipip/bootrom/bootrom.rv32.img differ
diff --git a/src/main/resources/testchipip/bootrom/bootrom.rv64.img b/src/main/resources/testchipip/bootrom/bootrom.rv64.img
index f746c2db..d42dfb22 100755
Binary files a/src/main/resources/testchipip/bootrom/bootrom.rv64.img and b/src/main/resources/testchipip/bootrom/bootrom.rv64.img differ
diff --git a/src/main/resources/testchipip/csrc/testchip_tsi.cc b/src/main/resources/testchipip/csrc/testchip_tsi.cc
index ecec1a02..9ad47cd3 100644
--- a/src/main/resources/testchipip/csrc/testchip_tsi.cc
+++ b/src/main/resources/testchipip/csrc/testchip_tsi.cc
@@ -3,10 +3,25 @@
 testchip_tsi_t::testchip_tsi_t(int argc, char** argv, bool can_have_loadmem) : tsi_t(argc, argv)
 {
   has_loadmem = false;
+  init_writes = std::vector<std::pair<uint64_t, uint32_t>>();
+  write_hart0_msip = true;
+
   std::vector<std::string> args(argv + 1, argv + argc);
   for (auto& arg : args) {
     if (arg.find("+loadmem=") == 0)
       has_loadmem = can_have_loadmem;
+    if (arg.find("+init_write=0x") == 0) {
+      auto d = arg.find(":0x");
+      if (d == std::string::npos) {
+        throw std::invalid_argument("Improperly formatted +init_write argument");
+      }
+      uint64_t addr = strtoull(arg.substr(14, d - 14).c_str(), 0, 16);
+      uint32_t val = strtoull(arg.substr(d + 3).c_str(), 0, 16);
+
+      init_writes.push_back(std::make_pair(addr, val));
+    }
+    if (arg.find("+no_hart0_msip") == 0)
+      write_hart0_msip = false;
   }
 }
 
@@ -28,3 +43,12 @@ void testchip_tsi_t::read_chunk(addr_t taddr, size_t nbytes, void* dst)
     tsi_t::read_chunk(taddr, nbytes, dst);
   }
 }
+
+void testchip_tsi_t::reset()
+{
+  for (auto p : init_writes) {
+    write_chunk(p.first, sizeof(uint32_t), &p.second);
+  }
+  if (write_hart0_msip)
+    tsi_t::reset();
+}
diff --git a/src/main/resources/testchipip/csrc/testchip_tsi.h b/src/main/resources/testchipip/csrc/testchip_tsi.h
index cc90810c..94d7ac45 100644
--- a/src/main/resources/testchipip/csrc/testchip_tsi.h
+++ b/src/main/resources/testchipip/csrc/testchip_tsi.h
@@ -22,10 +22,13 @@ class testchip_tsi_t : public tsi_t
  protected:
   virtual void load_mem_write(addr_t taddr, size_t nbytes, const void* src) { };
   virtual void load_mem_read(addr_t taddr, size_t nbytes, void* dst) { };
+  void reset() override;
   bool has_loadmem;
 
  private:
 
   bool is_loadmem;
+  bool write_hart0_msip;
+  std::vector<std::pair<uint64_t, uint32_t>> init_writes;
 };
 #endif
diff --git a/src/main/scala/BootAddrReg.scala b/src/main/scala/BootAddrReg.scala
new file mode 100644
index 00000000..43c33972
--- /dev/null
+++ b/src/main/scala/BootAddrReg.scala
@@ -0,0 +1,38 @@
+package testchipip
+
+import chisel3._
+import chisel3.experimental.{IO}
+import freechips.rocketchip.config.{Parameters, Field}
+import freechips.rocketchip.diplomacy._
+import freechips.rocketchip.tilelink._
+import freechips.rocketchip.devices.tilelink._
+import freechips.rocketchip.regmapper._
+import freechips.rocketchip.subsystem._
+import freechips.rocketchip.util._
+import freechips.rocketchip.tile._
+import freechips.rocketchip.prci._
+
+
+case class BootAddrRegParams(
+  defaultBootAddress: BigInt = 0x80000000L, // This should be DRAM_BASE
+  bootRegAddress: BigInt = 0x4000,
+  slaveWhere: TLBusWrapperLocation = PBUS
+)
+case object BootAddrRegKey extends Field[BootAddrRegParams](BootAddrRegParams())
+
+trait HasPeripheryBootAddrReg { this: BaseSubsystem =>
+  val params = p(BootAddrRegKey)
+
+  val tlbus = locateTLBusWrapper(params.slaveWhere)
+
+  val device = new SimpleDevice("boot-address-reg", Nil)
+
+  tlbus {
+    val node = TLRegisterNode(Seq(AddressSet(params.bootRegAddress, 4096-1)), device, "reg/control", beatBytes=tlbus.beatBytes)
+    tlbus.toVariableWidthSlave(Some("boot-address-reg")) { node }
+    InModuleBody {
+      val bootAddrReg = RegInit(params.defaultBootAddress.U(p(XLen).W))
+      node.regmap(0 -> RegField.bytes(bootAddrReg))
+    }
+  }
+}
diff --git a/src/main/scala/CustomBootPin.scala b/src/main/scala/CustomBootPin.scala
new file mode 100644
index 00000000..3e17df6d
--- /dev/null
+++ b/src/main/scala/CustomBootPin.scala
@@ -0,0 +1,86 @@
+package testchipip
+
+import chisel3._
+import chisel3.util._
+import chisel3.experimental.{IO}
+import freechips.rocketchip.config._
+import freechips.rocketchip.diplomacy._
+import freechips.rocketchip.tilelink._
+import freechips.rocketchip.devices.tilelink._
+import freechips.rocketchip.regmapper._
+import freechips.rocketchip.subsystem._
+import freechips.rocketchip.util._
+import freechips.rocketchip.tile._
+import freechips.rocketchip.prci._
+
+case class CustomBootPinParams(
+  customBootAddress: BigInt = 0x80000000L, // Default is DRAM_BASE
+  masterWhere: TLBusWrapperLocation = CBUS // This needs to write to clint and bootaddrreg, which are on CBUS/PBUS
+)
+
+case object CustomBootPinKey extends Field[Option[CustomBootPinParams]](Some(CustomBootPinParams()))
+
+class WithCustomBootPinAltAddr(address: BigInt) extends Config((site, here, up) => {
+  case CustomBootPinKey => up(CustomBootPinKey, site).map(p => p.copy(customBootAddress = address))
+})
+
+trait CanHavePeripheryCustomBootPin { this: BaseSubsystem =>
+  val custom_boot_pin = p(CustomBootPinKey).map { params =>
+    val tlbus = locateTLBusWrapper(params.masterWhere)
+    val clientParams = TLMasterPortParameters.v1(
+      clients = Seq(TLMasterParameters.v1(
+        name = "custom-boot",
+        sourceId = IdRange(0, 1),
+      )),
+      minLatency = 1
+    )
+
+    val inner_io = tlbus {
+      val node = TLClientNode(Seq(clientParams))
+      tlbus.coupleFrom(s"port_named_custom_boot_pin") ({ _ := node })
+
+      InModuleBody {
+        val custom_boot = IO(Input(Bool())).suggestName("custom_boot")
+        val (tl, edge) = node.out(0)
+        val inactive :: waiting_bootaddr_reg_a :: waiting_bootaddr_reg_d :: waiting_msip_a :: waiting_msip_d :: dead :: Nil = Enum(6)
+        val state = RegInit(inactive)
+        tl.a.valid := false.B
+        tl.a.bits := DontCare
+        tl.d.ready := true.B
+        switch (state) {
+          is (inactive) { when (custom_boot) { state := waiting_bootaddr_reg_a } }
+          is (waiting_bootaddr_reg_a) {
+            tl.a.valid := true.B
+            tl.a.bits := edge.Put(
+              toAddress = p(BootAddrRegKey).bootRegAddress.U,
+              fromSource = 0.U,
+              lgSize = 2.U,
+              data = params.customBootAddress.U
+            )._2
+            when (tl.a.fire()) { state := waiting_bootaddr_reg_d }
+          }
+          is (waiting_bootaddr_reg_d) { when (tl.d.fire()) { state := waiting_msip_a } }
+          is (waiting_msip_a) {
+            tl.a.valid := true.B
+            tl.a.bits := edge.Put(
+              toAddress = (p(CLINTKey).get.baseAddress + CLINTConsts.msipOffset(0)).U, // msip for hart0
+              fromSource = 0.U,
+              lgSize = log2Ceil(CLINTConsts.msipBytes).U,
+              data = 1.U
+            )._2
+            when (tl.a.fire()) { state := waiting_msip_d }
+          }
+          is (waiting_msip_d) { when (tl.d.fire()) { state := dead } }
+          is (dead) { when (!custom_boot) { state := inactive } }
+        }
+        custom_boot
+      }
+    }
+    val outer_io = InModuleBody {
+      val custom_boot = IO(Input(Bool())).suggestName("custom_boot")
+      inner_io := custom_boot
+      custom_boot
+    }
+    outer_io
+  }
+}
diff --git a/src/main/scala/TileResetCtrl.scala b/src/main/scala/TileResetCtrl.scala
index e18a0d35..e9c55932 100644
--- a/src/main/scala/TileResetCtrl.scala
+++ b/src/main/scala/TileResetCtrl.scala
@@ -38,14 +38,14 @@ class TLTileResetCtrl(w: Int, params: TileResetCtrlParams, tile_prci_domains: Se
 
   lazy val module = new LazyModuleImp(this) {
     val nTiles = p(TilesLocated(InSubsystem)).size
-    require (nTiles <= 4096)
+    require (nTiles <= 4096 / 4)
     val r_tile_resets = (0 until nTiles).map({ i =>
       withReset (asyncResetSinkNode.in.head._1.reset) {
         Module(new AsyncResetRegVec(w=1, init=(if (params.initResetHarts.contains(i)) 1 else 0)))
       }
     })
     node.regmap((0 until nTiles).map({ i =>
-      i -> Seq(RegField.rwReg(1, r_tile_resets(i).io)),
+      i * 4 -> Seq(RegField.rwReg(1, r_tile_resets(i).io)),
     }): _*)
 
     val tileMap = tile_prci_domains.zipWithIndex.map({ case (d, i) =>