diff --git a/gemma/src/chip8/computer.rs b/gemma/src/chip8/computer.rs
index 3c28114..2a293c6 100644
--- a/gemma/src/chip8/computer.rs
+++ b/gemma/src/chip8/computer.rs
@@ -91,7 +91,7 @@ impl Chip8Computer {
     }
 
     pub fn step_system(&mut self) -> &mut Chip8Computer {
-        debug!("Stepping System 1 Step");
+        println!("Stepping System 1 Step");
         // read the next instruction
         let local_memory = &self.memory;
 
@@ -107,6 +107,7 @@ impl Chip8Computer {
 
         match self.state {
             Chip8CpuStates::WaitingForInstruction => {
+                println!("Ticking sound, delay, video");
                 self.sound_timer.tick();
                 self.delay_timer.tick();
                 self.video_memory.tick();
diff --git a/gemma/src/chip8/instructions.rs b/gemma/src/chip8/instructions.rs
index 16e5a95..671a31b 100644
--- a/gemma/src/chip8/instructions.rs
+++ b/gemma/src/chip8/instructions.rs
@@ -884,9 +884,6 @@ impl Chip8CpuInstructions {
                     value_to_poke = (y_register - x_register) as u16;
                     1
                 };
-
-                debug!("SUB CARRY -> REGISTER 1 = [0x{x:02x}] / [{x_register}] REGISTER 2 = [0x{y:02x}] / [{y_register}] SUB = {value_to_poke} CARRY = {new_value}");
-
                 input.registers.poke(*x, value_to_poke as u8);
                 input.registers.poke(0xf, new_value);
             }
@@ -938,8 +935,11 @@ impl Chip8CpuInstructions {
             // 0xBxnn Jump to Xnn+Vx
             JPX(vx_register, addr) => {
                 let x_reg_value: u16 = input.registers.peek(*vx_register) as u16;
-                let new_addr = *addr + x_reg_value;
-                input.registers.poke_i(new_addr);
+                let shifted_x_reg = x_reg_value << 8;
+                let added_addr = shifted_x_reg | addr;
+                let final_addr = added_addr + shifted_x_reg;
+                println!("JPX -> {x_reg_value:02x} {shifted_x_reg:04x} {added_addr:04x} {final_addr:04x}");
+                input.registers.poke_i(final_addr);
             }
             Chip8CpuInstructions::RND(x, byte) => {
                 // Cxkk - RND Vx, byte
diff --git a/gemma/tests/unit_tests.rs b/gemma/tests/unit_tests.rs
index 5802a51..4340bfb 100644
--- a/gemma/tests/unit_tests.rs
+++ b/gemma/tests/unit_tests.rs
@@ -1,6 +1,7 @@
 use log::debug;
 use rand::random;
 use gemma::chip8::computer::Chip8Computer;
+use gemma::chip8::cpu_states::Chip8CpuStates::WaitingForInstruction;
 use gemma::chip8::delay_timer::DelayTimer;
 use gemma::chip8::instructions::Chip8CpuInstructions;
 use gemma::chip8::instructions::Chip8CpuInstructions::JPX;
@@ -9,6 +10,7 @@ use gemma::chip8::quirk_modes::QuirkMode::{Chip8, SChipModern, XOChip};
 use gemma::chip8::registers::Chip8Registers;
 use gemma::chip8::sound_timer::SoundTimer;
 use gemma::chip8::stack::Chip8Stack;
+use gemma::chip8::system_memory::Chip8SystemMemory;
 use gemma::chip8::util::InstructionUtil;
 use gemma::chip8::video::{Chip8Video, Chip8VideoModes};
 use gemma::constants::*;
@@ -1358,7 +1360,46 @@ fn instruction_jpx() {
     x.registers.poke(0x01, 0x04);
     // ...use (x1)+0x134
     let to_execute = JPX(0x01, 0x34);
-    // expect to set PC to 0x524
+    // expect to set PC to 0x834
     to_execute.execute(&mut x);
-    assert_eq!(x.registers.peek_pc(), 0x524);
+    assert_eq!(x.registers.peek_i(), 0x834);
+}
+
+#[test]
+fn instruction_ldrd() {
+    let mut x = Chip8Computer::new();
+    x.state = WaitingForInstruction;
+    x.delay_timer.set_timer(0x01);
+    Chip8CpuInstructions::LDRD(0x01).execute(&mut x);
+    assert_eq!(x.registers.peek(0x01), 0x01);
+    x.delay_timer.set_timer(0xff);
+    Chip8CpuInstructions::LDRD(0x0).execute(&mut x);
+    assert_eq!(x.registers.peek(0x00), 0xff);
+    x.step_system();
+    x.step_system();
+    x.step_system();
+    x.step_system();
+    Chip8CpuInstructions::LDRD(0x0).execute(&mut x);
+    assert_eq!(x.registers.peek(0x0), 0xfb);
+}
+
+#[test]
+fn video_hires_loop_check() {
+    let max_address = SCHIP_VIDE_MEMORY;
+    let x = build_checkboard_hd();
+    x.peek((max_address + 1) as u16);
+    // if we got here we didn't explode!
+    assert!(true);
+}
+
+#[test]
+fn sound_timer_default() {
+    let x = SoundTimer::default();
+    assert_eq!(x.current(), 0);
+}
+
+#[test]
+fn system_memory_new() {
+    let x = Chip8SystemMemory::new();
+    assert!(true);
 }
\ No newline at end of file