diff --git a/apple2/apple2.go b/apple2/apple2.go
index 827dca6..9a03c3c 100644
--- a/apple2/apple2.go
+++ b/apple2/apple2.go
@@ -13,16 +13,18 @@ type Apple2 struct {
 	io         *ioC0Page
 	cards      []cardBase
 	isApple2e  bool
+	panicSS    bool
 	activeSlot int // Slot that has the addressing 0xc800 to 0ccfff
 }
 
 // NewApple2 instantiates an apple2
-func NewApple2(romFile string) *Apple2 {
+func NewApple2(romFile string, panicSS bool) *Apple2 {
 	var a Apple2
 	a.mmu = newMemoryManager(&a)
 	a.cpu = core6502.NewNMOS6502(a.mmu)
 	a.loadRom(romFile)
 	a.mmu.resetPaging()
+	a.panicSS = panicSS
 
 	// Set the io in 0xc000
 	a.io = newIoC0Page(&a)
diff --git a/apple2/ioC0Page.go b/apple2/ioC0Page.go
index 3cccef8..b38e07a 100644
--- a/apple2/ioC0Page.go
+++ b/apple2/ioC0Page.go
@@ -72,10 +72,11 @@ func (p *ioC0Page) Peek(address uint8) uint8 {
 	//fmt.Printf("Peek on $C0%02x ", address)
 	ss := p.softSwitchesR[address]
 	if ss == nil {
-		//panic(fmt.Sprintf("Unknown softswitch on read to 0xC0%02x", address))
+		if p.apple2.panicSS {
+			panic(fmt.Sprintf("Unknown softswitch on read to 0xC0%02x", address))
+		}
 		return 0
 	}
-
 	return ss(p)
 }
 
@@ -83,7 +84,9 @@ func (p *ioC0Page) Poke(address uint8, value uint8) {
 	//fmt.Printf("Poke on $C0%02x with %02x ", address, value)
 	ss := p.softSwitchesW[address]
 	if ss == nil {
-		//panic(fmt.Sprintf("Unknown softswitch on write to 0xC0%02x", address))
+		if p.apple2.panicSS {
+			panic(fmt.Sprintf("Unknown softswitch on write to 0xC0%02x", address))
+		}
 		return
 	}
 	ss(p, value)
diff --git a/main.go b/main.go
index 8d3c11c..bd3d70e 100644
--- a/main.go
+++ b/main.go
@@ -1,22 +1,46 @@
 package main
 
 import (
+	"flag"
 	"go6502/apple2"
 	"go6502/apple2sdl"
 )
 
 func main() {
+	romFile := flag.String(
+		"rom",
+		"apple2/romdumps/Apple2_Plus.rom",
+		"main rom file")
+	disk2RomFile := flag.String(
+		"diskRom",
+		"apple2/romdumps/DISK2.rom",
+		"rom file for the disk drive controller")
+	diskImage := flag.String(
+		"disk",
+		"../dos33.dsk",
+		"file to load on the first disk drive")
+	useSdl := flag.Bool(
+		"sdl",
+		true,
+		"use SDL")
+	panicSS := flag.Bool(
+		"panicss",
+		false,
+		"panic if a not implemented softwtich is used")
+	flag.Parse()
+
 	//romFile := "apple2/romdumps/Apple2.rom"
-	romFile := "apple2/romdumps/Apple2_Plus.rom"
+	//romFile := "apple2/romdumps/Apple2_Plus.rom"
 	//romFile := "apple2/romdumps/Apple2e.rom"
-	disk2RomFile := "apple2/romdumps/DISK2.rom"
-	diskImage := "../dos33.dsk"
+	//disk2RomFile := "apple2/romdumps/DISK2.rom"
+	//diskImage := "../dos33.dsk"
+	//diskImage := "../Apex II - Apple II Diagnostic (v4.7-1986).DSK"
+	//diskImage := "../A2Diag.v4.1.SDK"
 
 	log := false
-	sdl := true
-	a := apple2.NewApple2(romFile)
-	a.AddDisk2(disk2RomFile, diskImage)
-	if sdl {
+	a := apple2.NewApple2(*romFile, *panicSS)
+	a.AddDisk2(*disk2RomFile, *diskImage)
+	if *useSdl {
 		apple2sdl.SDLRun(a)
 	} else {
 		a.Run(log, true)