diff --git a/code/os/06-interrupts/platform.h b/code/os/06-interrupts/platform.h
index e706ae7..c853063 100644
--- a/code/os/06-interrupts/platform.h
+++ b/code/os/06-interrupts/platform.h
@@ -46,7 +46,7 @@
  * #define VIRT_PLIC_HART_CONFIG "MS"
  * #define VIRT_PLIC_NUM_SOURCES 127
  * #define VIRT_PLIC_NUM_PRIORITIES 7
- * #define VIRT_PLIC_PRIORITY_BASE 0x04
+ * #define VIRT_PLIC_PRIORITY_BASE 0x00
  * #define VIRT_PLIC_PENDING_BASE 0x1000
  * #define VIRT_PLIC_ENABLE_BASE 0x2000
  * #define VIRT_PLIC_ENABLE_STRIDE 0x80
diff --git a/code/os/07-hwtimer/platform.h b/code/os/07-hwtimer/platform.h
index 2694308..def36d6 100644
--- a/code/os/07-hwtimer/platform.h
+++ b/code/os/07-hwtimer/platform.h
@@ -46,7 +46,7 @@
  * #define VIRT_PLIC_HART_CONFIG "MS"
  * #define VIRT_PLIC_NUM_SOURCES 127
  * #define VIRT_PLIC_NUM_PRIORITIES 7
- * #define VIRT_PLIC_PRIORITY_BASE 0x04
+ * #define VIRT_PLIC_PRIORITY_BASE 0x00
  * #define VIRT_PLIC_PENDING_BASE 0x1000
  * #define VIRT_PLIC_ENABLE_BASE 0x2000
  * #define VIRT_PLIC_ENABLE_STRIDE 0x80
diff --git a/code/os/08-preemptive/platform.h b/code/os/08-preemptive/platform.h
index 2694308..def36d6 100644
--- a/code/os/08-preemptive/platform.h
+++ b/code/os/08-preemptive/platform.h
@@ -46,7 +46,7 @@
  * #define VIRT_PLIC_HART_CONFIG "MS"
  * #define VIRT_PLIC_NUM_SOURCES 127
  * #define VIRT_PLIC_NUM_PRIORITIES 7
- * #define VIRT_PLIC_PRIORITY_BASE 0x04
+ * #define VIRT_PLIC_PRIORITY_BASE 0x00
  * #define VIRT_PLIC_PENDING_BASE 0x1000
  * #define VIRT_PLIC_ENABLE_BASE 0x2000
  * #define VIRT_PLIC_ENABLE_STRIDE 0x80
diff --git a/code/os/09-lock/platform.h b/code/os/09-lock/platform.h
index 2694308..def36d6 100644
--- a/code/os/09-lock/platform.h
+++ b/code/os/09-lock/platform.h
@@ -46,7 +46,7 @@
  * #define VIRT_PLIC_HART_CONFIG "MS"
  * #define VIRT_PLIC_NUM_SOURCES 127
  * #define VIRT_PLIC_NUM_PRIORITIES 7
- * #define VIRT_PLIC_PRIORITY_BASE 0x04
+ * #define VIRT_PLIC_PRIORITY_BASE 0x00
  * #define VIRT_PLIC_PENDING_BASE 0x1000
  * #define VIRT_PLIC_ENABLE_BASE 0x2000
  * #define VIRT_PLIC_ENABLE_STRIDE 0x80
diff --git a/code/os/10-swtimer/platform.h b/code/os/10-swtimer/platform.h
index 2694308..def36d6 100644
--- a/code/os/10-swtimer/platform.h
+++ b/code/os/10-swtimer/platform.h
@@ -46,7 +46,7 @@
  * #define VIRT_PLIC_HART_CONFIG "MS"
  * #define VIRT_PLIC_NUM_SOURCES 127
  * #define VIRT_PLIC_NUM_PRIORITIES 7
- * #define VIRT_PLIC_PRIORITY_BASE 0x04
+ * #define VIRT_PLIC_PRIORITY_BASE 0x00
  * #define VIRT_PLIC_PENDING_BASE 0x1000
  * #define VIRT_PLIC_ENABLE_BASE 0x2000
  * #define VIRT_PLIC_ENABLE_STRIDE 0x80
diff --git a/code/os/11-syscall/platform.h b/code/os/11-syscall/platform.h
index 2694308..def36d6 100644
--- a/code/os/11-syscall/platform.h
+++ b/code/os/11-syscall/platform.h
@@ -46,7 +46,7 @@
  * #define VIRT_PLIC_HART_CONFIG "MS"
  * #define VIRT_PLIC_NUM_SOURCES 127
  * #define VIRT_PLIC_NUM_PRIORITIES 7
- * #define VIRT_PLIC_PRIORITY_BASE 0x04
+ * #define VIRT_PLIC_PRIORITY_BASE 0x00
  * #define VIRT_PLIC_PENDING_BASE 0x1000
  * #define VIRT_PLIC_ENABLE_BASE 0x2000
  * #define VIRT_PLIC_ENABLE_STRIDE 0x80