--- z80pack-1.24/cpmsim/srcsim/iosim.c	2014-07-16 23:52:45.000000000 +0200
+++ z80pack/cpmsim/srcsim/iosim.c	2014-09-17 20:17:01.000000000 +0200
@@ -40,6 +40,8 @@
  * 02-MAR-14 source cleanup and improvements
  * 03-MAI-14 improved network code, telnet negotiation rewritten
  * 16-JUL-14 unused I/O ports need to return FF, see survey.mac
+ * 17-SEP-14 FDC error 8 for DMA overrun, as reported by Alan Cox
+ * 17_SEP-14 fixed bug in MMU bank select, as reported by Alan Cox
  */
 
 /*
@@ -2149,6 +2151,7 @@
  *	  5 - read error
  *	  6 - write error
  *	  7 - illegal command to FDC
+ *        8 - DMA overrun > 0xffff
  */
 static void fdco_out(BYTE data)
 {
@@ -2165,6 +2168,10 @@
 		status = 3;
 		return;
 	}
+	if (dmadh == 0xff && dmadl > 0x80) {
+		status = 8;
+		return;
+	}
 	pos = (((long)track) * ((long)disks[drive].sectors) + sector - 1) << 7;
 	if (lseek(*disks[drive].fd, pos, SEEK_SET) == -1L) {
 		status = 4;
@@ -2300,8 +2307,9 @@
 {
 	if (data == selbnk)
 		return;
-	if (data > maxbnk) {
-		printf("Try to select unallocated bank %d\r\n", data);
+	if (data >= maxbnk) {
+		printf("0x%04lx: Try to select unallocated bank %d\r\n",
+		       PC - ram, data);
 		exit(1);
 	}
 	//printf("SIM: memory select bank %d from %d\r\n", data, PC-ram);