diff --git a/cgdoom/cgdoom-ui.c b/cgdoom/cgdoom-ui.c
index cb78d81..1b77bf3 100644
--- a/cgdoom/cgdoom-ui.c
+++ b/cgdoom/cgdoom-ui.c
@@ -172,7 +172,7 @@ void UI_Checkbox(int x, int y, int checked)
 void UI_FileMappingProgressBar(int size_mapped, int size_total)
 {
 	const int w=192, h=5;
-	const int x0=(WIDTH-w)/2, y0=HEIGHT-20;
+	const int x0=(WIDTH-w)/2, y0=HEIGHT-10;
 	const int pos = x0 + (w * size_mapped) / size_total;
 
 	for(int x = x0; x < x0+w; x++)
@@ -206,7 +206,7 @@ void Layout_Init(Layout *l)
 void Layout_StartFrame(Layout *l)
 {
 	l->focus_count = 0;
-	l->y = 12;
+	l->y = 10;
 }
 
 void Layout_EndFrame(Layout *l)
@@ -377,7 +377,7 @@ int Layout_Event(Layout *l, int key)
 
 int UI_Main(WADFileInfo *wads, int wad_count, int *dev_info, int *use_mmap,
 	int *startmap, int *startepisode, int *trustunaligned,
-	int *autostart, int *enabledemos)
+	int *autostart, int *enabledemos, int *enable2MBline)
 {
 	Layout l;
 	Layout_Init(&l);
@@ -387,7 +387,7 @@ int UI_Main(WADFileInfo *wads, int wad_count, int *dev_info, int *use_mmap,
 		Bdisp_AllClr_VRAM();
 		Layout_StartFrame(&l);
 		Layout_CenteredText(&l, "CGDoom for fx-CG 50 and Graph 90+E");
-		Layout_Spacing(&l, 12);
+		Layout_Spacing(&l, 10);
 
 		for(int i = 0; i < wad_count; i++)
 		{
@@ -410,17 +410,19 @@ int UI_Main(WADFileInfo *wads, int wad_count, int *dev_info, int *use_mmap,
 				(wads[i].size % 1000000) / 100000);
 		}
 
-		Layout_Spacing(&l, 12);
+		Layout_Spacing(&l, 10);
 		Layout_Integer(&l, "Start at episode:", startepisode);
 		Layout_Integer(&l, "Start at map:", startmap);
 		Layout_Text(&l, "Title screen:",
 			*autostart ? "Skip" :
 			!*enabledemos ? "No demos" : "Full");
 
-		Layout_Spacing(&l, 12);
+		Layout_Spacing(&l, 10);
 		Layout_Checkbox(&l, "Developer info:", dev_info);
 		Layout_Checkbox(&l, "Map file to memory:", use_mmap);
 		Layout_Checkbox(&l, "Trust unaligned lumps:", trustunaligned);
+		if(enable2MBline)
+			Layout_Checkbox(&l, "Use memory beyond 2MB:", enable2MBline);
 		Layout_EndFrame(&l);
 		Bdisp_PutDisp_DD();
 
diff --git a/cgdoom/cgdoom-ui.h b/cgdoom/cgdoom-ui.h
index 5b0e0a4..1244e92 100644
--- a/cgdoom/cgdoom-ui.h
+++ b/cgdoom/cgdoom-ui.h
@@ -69,7 +69,8 @@ int UI_Main(WADFileInfo *wads, int wad_count,
     int *startepisode,    /* Warp to this episode */
     int *trustunaligned,  /* Trust unaligned lumps */
     int *autostart,       /* Skip title screen, straight to gameplay */
-    int *enabledemos      /* Enable demos on the title screen */
+    int *enabledemos,     /* Enable demos on the title screen */
+    int *enable2MBline    /* Enable memory past the 2MB line */
 );
 
 /* Show an error with custom formatting. */
diff --git a/cgdoom/cgdoom.c b/cgdoom/cgdoom.c
index 002336b..b40b313 100644
--- a/cgdoom/cgdoom.c
+++ b/cgdoom/cgdoom.c
@@ -383,6 +383,7 @@ static SectorIndexInfo *gIndex = NULL;
 int CGD_TrustUnalignedLumps = 1;
 int CGD_EnableDemos = 0;
 int CGD_SingleEpisodeUltimate = 0;
+int CGD_2MBLineMemory = 0;
 
 /* Performance counters */
 struct CGD_Perf CGD_Perf;
@@ -621,6 +622,20 @@ void abort(void){
 
 #endif /* CG_EMULATOR */
 
+static int FindZeroedMemory(void *start)
+{
+	/* Look for zero-longwords every 16 bytes */
+	int size = 0;
+
+	/* Limit to 6 MB since the fx-CG 50 doesn't have any more memory and
+	   anything after the RAM is likely to be zero non-writable */
+	while(size < CGDOOM_2MBLINEMEMORY_MAX && !*(uint32_t *)(start + size))
+		size += 16;
+
+	/* Round down to a multiple of 4096 */
+	return size & ~0xfff;
+}
+
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 int main(void)
 {
@@ -644,9 +659,16 @@ int main(void)
 	int wad_count = FindWADs(wads, 16);
 
 	int dev_info = 0;
+
+	/* Allow the user to use memory past the 2 MB line on known OS versions */
+	int *enable_2MBline=NULL;
+	char const *osv = (void *)0x80020020;
+	if(!strncmp(osv, "03.", 3) && osv[3] <= '5') // 3.50 or earlier
+		enable_2MBline = &CGD_2MBLineMemory;
+
 	int choice = UI_Main(wads, wad_count, &dev_info, &gWADmethod,
 		&startmap, &startepisode, &CGD_TrustUnalignedLumps, &autostart_,
-		&CGD_EnableDemos);
+		&CGD_EnableDemos, enable_2MBline);
 	if(choice < 0)
 		return 1;
 
@@ -664,9 +686,13 @@ int main(void)
 
 	unsigned tmp=((unsigned)getSecondaryVramAddress()+3)&(~3);
 	SaveVRAMBuffer = (unsigned char*)tmp;
-	/* Graph 90+E: RAM starts at 0x0c000000 in physical memory */
+	/* fx-CG 50 / Graph 90+E: RAM starts at 0x0c000000 in physical memory */
 	SystemStack = (void *)0xac0f0000;
 
+	/* Determine how much RAM is zeroed out at 2 MB */
+	if(CGD_2MBLineMemory)
+		CGD_2MBLineMemory = FindZeroedMemory((void *)0xac200000);
+
 	/* Setup access to WAD file */
 	#ifdef CG_EMULATOR
 	gWADmethod = CGDOOM_WAD_BFILE;
diff --git a/cgdoom/i_system.c b/cgdoom/i_system.c
index cc938ca..e4c9f48 100644
--- a/cgdoom/i_system.c
+++ b/cgdoom/i_system.c
@@ -92,7 +92,7 @@ byte *I_ScreenBase(int screen)
 /* On the calculator, scrap every possible bit of RAM */
 byte* I_ZoneBase (int*  size, int i)
 {
-    if (i == 0)
+    if (i-- == 0)
     {
         /* System stack (~500 kiB) */
         *size = RAM_I_Zone_SIZE;
@@ -100,15 +100,21 @@ byte* I_ZoneBase (int*  size, int i)
         ASSERT(RAM_I_Zone_SIZE <= SYSTEM_STACK_SIZE);
         return mb_mainzone;
     }
-    if (i == 1)
+    if (i-- == 0)
     {
         /* Unused part of user stack (~200 kiB); provided by linker script */
         extern byte sextra, eextra;
         *size = &eextra - &sextra;
         return &sextra;
     }
+    if (CGD_2MBLineMemory && i-- == 0)
+    {
+        /* Memory beyond the 2MB line */
+        *size = CGD_2MBLineMemory;
+        return (void *)0x8c200000;
+    }
     #ifdef CGDOOM_DIRECT_R61524
-    if (i == 2)
+    if (i-- == 0)
     {
         /* Secondary VRAM (screen buffers being in the main VRAM because we're
            doing direct access so we don't need Bdisp_PutDisp_DD() */
diff --git a/cgdoom/st_stuff.c b/cgdoom/st_stuff.c
index f426c35..4ed51c6 100644
--- a/cgdoom/st_stuff.c
+++ b/cgdoom/st_stuff.c
@@ -486,7 +486,7 @@ void CGFreeMem()
     if (!ptr)
       break;
 
-    sprintf(message+strlen(message), "%s%d/%d kB", (i ? ", " : ""),
+    sprintf(message+strlen(message), "%s%d/%dk", (i ? ", " : ""),
       Z_FreeMemory(i) >> 10, size >> 10);
   }
 
diff --git a/src-cg/platform.h b/src-cg/platform.h
index 4a40522..62e7eab 100644
--- a/src-cg/platform.h
+++ b/src-cg/platform.h
@@ -81,6 +81,12 @@ extern int CGD_TrustUnalignedLumps;
 # define CGDOOM_SCREENS_BASE SaveVRAMBuffer
 #endif
 
+/* Amount of extra memory past the 2 MB line that we deem safe to access. */
+extern int CGD_2MBLineMemory;
+
+/* Maximum amount of memory beyond the 2 MB line */
+#define CGDOOM_2MBLINEMEMORY_MAX (6 << 20)
+
 //---
 
 #include "keyboard.hpp"