--- nono/util/runx/iocscall.cpp	2026/04/29 17:05:27	1.1
+++ nono/util/runx/iocscall.cpp	2026/04/29 17:05:36	1.1.1.2
@@ -32,6 +32,25 @@ iocscall(pid_t pid, struct reg *reg)
 	int have_fpu = 1;	// XXX
 
 	switch (callno) {
+	 case 0x80:	// _B_INTVCS
+	 {
+		uint32 num = RegD(1);
+		uint32 newaddr = RegA(1);
+		uint32 oldaddr;
+		if (num < 0x100) {
+			// 例外ベクタ。
+			oldaddr = readmem4(num * 4);
+			writemem4(num * 4, newaddr);
+			TRACE(pc, "IOCS _B_INTVCS(#$%04x, $%06x) -> $%06x",
+				num, newaddr, oldaddr);
+		} else {
+			// 未対応。
+			TRACE(pc, "IOCS _B_INTVCS(#$%04x, $%06x) Not supported",
+				num, newaddr);
+		}
+		break;
+	 }
+
 	 case 0x82:	// _B_BPEEK
 	 {
 		uint32 addr = RegA(1);