-#define PSXGPU_LCF (1<<31)
-#define PSXGPU_nBUSY (1<<26)
-#define PSXGPU_ILACE (1<<22)
+#define PSXGPU_LCF (1<<31)
+#define PSXGPU_nBUSY (1<<26)
+#define PSXGPU_ILACE (1<<22)
+#define PSXGPU_DHEIGHT (1<<19)
+
+// both must be set for interlace to work
+#define PSXGPU_ILACE_BITS (PSXGPU_ILACE | PSXGPU_DHEIGHT)