diff --git a/XTMax/Code/XTMax/XTMax.ino b/XTMax/Code/XTMax/XTMax.ino
index 2ac3958..d80ac98 100644
--- a/XTMax/Code/XTMax/XTMax.ino
+++ b/XTMax/Code/XTMax/XTMax.ino
@@ -37,7 +37,10 @@
 //
 // Revision 7 01/12/2025
 // - Refactor SD card I/O
-// - Add support for 16-bit EMS page offsets.
+// - Add support for 16-bit EMS page offsets
+//
+// Revision 8 01/18/2024
+// - Add support for BIOS ROM extension (Boot ROM)
 //
 // Revision 8 01/20/2025
 // - Added chip select for a second PSRAM to allow access to 16 MB of Expanded RAM
@@ -71,6 +74,8 @@
 #include <stdint.h>
 #include <stdio.h>
 
+#include "bootrom.h"
+
 
 // Teensy 4.1 pin assignments
 //
@@ -573,6 +578,16 @@ inline void Mem_Read_Cycle() {
      
       GPIO8_DR = sd_pin_outputs + MUX_DATA_n_HIGH + CHRDY_OE_n_HIGH + DATA_OE_n_HIGH;
     }
+    else if (isa_address>=BOOTROM_ADDR && isa_address<BOOTROM_ADDR+sizeof(BOOTROM)) {   // Boot ROM
+      isa_data_out = BOOTROM[isa_address-BOOTROM_ADDR];
+      GPIO7_DR = GPIO7_DATA_OUT_UNSCRAMBLE + MUX_ADDR_n_LOW  + CHRDY_OUT_LOW + trigger_out;
+      GPIO8_DR = sd_pin_outputs + MUX_DATA_n_HIGH + CHRDY_OE_n_HIGH + DATA_OE_n_LOW;
+
+      while ( (gpio9_int&0xF0) != 0xF0 ) { gpio9_int = GPIO9_DR; }  // Wait here until cycle is complete
+
+      GPIO8_DR = sd_pin_outputs + MUX_DATA_n_HIGH + CHRDY_OE_n_HIGH + DATA_OE_n_HIGH;
+    }
+
     return;
 }
 
@@ -612,7 +627,6 @@ inline void Mem_Write_Cycle() {
       GPIO7_DR = GPIO7_DATA_OUT_UNSCRAMBLE + MUX_ADDR_n_LOW  + CHRDY_OUT_LOW + trigger_out;
       GPIO8_DR = sd_pin_outputs + MUX_DATA_n_HIGH + CHRDY_OE_n_HIGH + DATA_OE_n_HIGH;
     }   
-
     else if (isa_address<0xA0000)   {    // XTMax stores the full 640 KB conventional memory
       GPIO7_DR = GPIO7_DATA_OUT_UNSCRAMBLE + MUX_ADDR_n_HIGH  + CHRDY_OUT_LOW + trigger_out;
       GPIO8_DR = sd_pin_outputs + MUX_DATA_n_LOW + CHRDY_OE_n_HIGH + DATA_OE_n_HIGH;
diff --git a/XTMax/Code/XTMax/bootrom.h b/XTMax/Code/XTMax/bootrom.h
new file mode 100644
index 0000000..088eb8c
--- /dev/null
+++ b/XTMax/Code/XTMax/bootrom.h
@@ -0,0 +1,130 @@
+#define BOOTROM_ADDR 0xCE000
+unsigned char BOOTROM[] = {
+    85, 170, 4, 184, 0, 192, 142, 216, 142, 192, 190, 33, 224, 232, 1, 0,
+    203, 83, 49, 219, 172, 8, 192, 116, 6, 180, 14, 205, 16, 235, 245, 91,
+    195, 66, 111, 111, 116, 82, 79, 77, 32, 102, 111, 114, 32, 88, 84, 77,
+    97, 120, 32, 118, 48, 46, 49, 13, 10, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 93};
\ No newline at end of file
diff --git a/XTMax/Drivers/BootROM/.gitignore b/XTMax/Drivers/BootROM/.gitignore
new file mode 100644
index 0000000..28cb051
--- /dev/null
+++ b/XTMax/Drivers/BootROM/.gitignore
@@ -0,0 +1,2 @@
+bootrom
+bootrom.com
diff --git a/XTMax/Drivers/BootROM/.vscode/tasks.json b/XTMax/Drivers/BootROM/.vscode/tasks.json
new file mode 100644
index 0000000..2fee6de
--- /dev/null
+++ b/XTMax/Drivers/BootROM/.vscode/tasks.json
@@ -0,0 +1,20 @@
+{
+    // See https://go.microsoft.com/fwlink/?LinkId=733558
+    // for the documentation about the tasks.json format
+    "version": "2.0.0",
+    "tasks": [
+        {
+            "label": "Build with NASM",
+            "type": "shell",
+            "command": ".\\build.cmd",
+            "options": {
+                "cwd": "${workspaceFolder}"
+            },
+            "problemMatcher": [],
+            "group": {
+                "kind": "build",
+                "isDefault": true
+            }
+        }
+    ]
+}
diff --git a/XTMax/Drivers/BootROM/bootrom.asm b/XTMax/Drivers/BootROM/bootrom.asm
new file mode 100644
index 0000000..be59c27
--- /dev/null
+++ b/XTMax/Drivers/BootROM/bootrom.asm
@@ -0,0 +1,72 @@
+bits 16
+
+%ifndef AS_COM
+;
+; BIOS will look for the AA55 signature between C8000-DFFFF in 2KB increments.
+; We choose an address in that range.
+;
+org 0xce000
+dw 0AA55h
+db 4    ; times 512 bytes
+
+%else
+;
+; Building as a COM file for testing.
+;
+org 0x100
+
+%endif
+
+entry:
+%ifndef AS_COM
+    mov ax, 0xc000
+    mov ds, ax
+    mov es, ax
+%endif
+
+    mov si, welcome
+    call print_string
+
+
+%ifndef AS_COM
+    retf
+%else
+;
+; DOS exit program.
+;
+    mov ah, 0x4c
+    xor al, al
+    int 0x21
+%endif
+
+;
+; Utilities
+;
+
+print_string:
+    push bx
+    xor bx,bx
+.loop:
+    lodsb
+    or al, al
+    jz .done
+    mov ah, 0x0E
+    int 0x10
+    jmp .loop
+.done:
+    pop bx
+    ret
+
+;
+; Strings
+;
+
+welcome db 'BootROM for XTMax v0.1', 0x0D, 0x0A, 0
+
+%ifndef AS_COM
+;
+; Pad to 2KB. We will try to keep our ROM under that size.
+;
+times 2047-($-$$) db 0
+db 0    ; will be used to complete the checksum.
+%endif
\ No newline at end of file
diff --git a/XTMax/Drivers/BootROM/build.cmd b/XTMax/Drivers/BootROM/build.cmd
new file mode 100644
index 0000000..63e2c5a
--- /dev/null
+++ b/XTMax/Drivers/BootROM/build.cmd
@@ -0,0 +1,2 @@
+..\Driver_Build_Tools\NASM\nasm.exe -f bin -o bootrom.com -DAS_COM .\bootrom.asm
+..\Driver_Build_Tools\NASM\nasm.exe -f bin -o bootrom .\bootrom.asm & python checksum.py
diff --git a/XTMax/Drivers/BootROM/checksum.py b/XTMax/Drivers/BootROM/checksum.py
new file mode 100644
index 0000000..c6e5b13
--- /dev/null
+++ b/XTMax/Drivers/BootROM/checksum.py
@@ -0,0 +1,23 @@
+# https://stackoverflow.com/questions/53808694/how-do-i-format-a-python-list-as-an-initialized-c-array
+def to_c_array(values, ctype="float", name="table", formatter=str, colcount=8):
+    # apply formatting to each element
+    values = [formatter(v) for v in values]
+
+    # split into rows with up to `colcount` elements per row
+    rows = [values[i:i+colcount] for i in range(0, len(values), colcount)]
+
+    # separate elements with commas, separate rows with newlines
+    body = ',\n    '.join([', '.join(r) for r in rows])
+
+    # assemble components into the complete string
+    return '{} {}[] = {{\n    {}}};'.format(ctype, name, body)
+
+with open("bootrom", "rb") as f:
+    b = bytearray(f.read())
+# compute the checksum and store a byte to
+b[-1] = 256 - sum(b[0:-1]) & 0xff
+with open("bootrom", "wb") as f:
+    f.write(b)
+with open("../../Code/XTMax/bootrom.h", "w") as f:
+    f.write("#define BOOTROM_ADDR 0xCE000\n")
+    f.write(to_c_array(b, ctype="unsigned char", name="BOOTROM", colcount=16))