"Implement register mirroring"
https://github.com/mupen64plus/mupen64plus-core/pull/1119

Index: src/device/rcp/rdp/rdp_core.h
--- src/device/rcp/rdp/rdp_core.h.orig
+++ src/device/rcp/rdp/rdp_core.h
@@ -95,12 +95,12 @@ struct rdp_core
 
 static osal_inline uint32_t dpc_reg(uint32_t address)
 {
-    return (address & 0xffff) >> 2;
+    return (address & 0x1f) >> 2;
 }
 
 static osal_inline uint32_t dps_reg(uint32_t address)
 {
-    return (address & 0xffff) >> 2;
+    return (address & 0x1f) >> 2;
 }
 
 void init_rdp(struct rdp_core* dp,
