diff --git a/Makefile.libretro b/Makefile.libretro
index 4cc673f..b887095 100644
--- a/Makefile.libretro
+++ b/Makefile.libretro
@@ -440,8 +440,8 @@ LIBRETRO_CFLAGS += $(BPP_DEFINES) \
 		$(ENDIANNESS_DEFINES) \
 		$(PLATFORM_DEFINES) \
 		-D__LIBRETRO__ \
-		-DM68K_ALLOW_OVERCLOCK \
-		-DZ80_ALLOW_OVERCLOCK
+		-DM68K_OVERCLOCK_SHIFT=20 \
+		-DZ80_OVERCLOCK_SHIFT=20
 
 ifneq (,$(findstring msvc,$(platform)))
    LIBRETRO_CFLAGS += -DINLINE="static _inline"
diff --git a/core/m68k/m68k.h b/core/m68k/m68k.h
index 93bb033..0aed500 100644
--- a/core/m68k/m68k.h
+++ b/core/m68k/m68k.h
@@ -268,8 +268,8 @@ typedef struct
 
   uint address_space;   /* Current FC code */
 
-#ifdef M68K_ALLOW_OVERCLOCK
-  uint8 overclock_ratio;
+#ifdef M68K_OVERCLOCK_SHIFT
+  int cycle_ratio;
 #endif
 
   /* Callbacks to host */
diff --git a/core/m68k/m68kcpu.c b/core/m68k/m68kcpu.c
index 245bef9..37020bd 100644
--- a/core/m68k/m68kcpu.c
+++ b/core/m68k/m68kcpu.c
@@ -319,8 +319,8 @@ void m68k_init(void)
   }
 #endif
 
-#ifdef M68K_ALLOW_OVERCLOCK
-  m68k.overclock_ratio = 1;
+#ifdef M68K_OVERCLOCK_SHIFT
+  m68k.cycle_ratio = 1 << M68K_OVERCLOCK_SHIFT;
 #endif
 
 #if M68K_EMULATE_INT_ACK == OPT_ON
diff --git a/core/m68k/m68kcpu.h b/core/m68k/m68kcpu.h
index 8b3355e..bd4f63f 100644
--- a/core/m68k/m68kcpu.h
+++ b/core/m68k/m68kcpu.h
@@ -514,8 +514,8 @@
 
 /* ---------------------------- Cycle Counting ---------------------------- */
 
-#ifdef M68K_ALLOW_OVERCLOCK
-#define USE_CYCLES(A) m68ki_cpu.cycles += (A) / m68ki_cpu.overclock_ratio
+#ifdef M68K_OVERCLOCK_SHIFT
+#define USE_CYCLES(A) m68ki_cpu.cycles += ((A) * m68ki_cpu.cycle_ratio) >> M68K_OVERCLOCK_SHIFT
 #else
 #define USE_CYCLES(A) m68ki_cpu.cycles += (A)
 #endif
diff --git a/core/m68k/s68kcpu.c b/core/m68k/s68kcpu.c
index 9665085..74bd04c 100644
--- a/core/m68k/s68kcpu.c
+++ b/core/m68k/s68kcpu.c
@@ -284,8 +284,8 @@ void s68k_init(void)
   }
 #endif
 
-#ifdef M68K_ALLOW_OVERCLOCK
-  s68k.overclock_ratio = 1;
+#ifdef M68K_OVERCLOCK_SHIFT
+  s68k.cycle_ratio = 1 << M68K_OVERCLOCK_SHIFT;
 #endif
 
 #if M68K_EMULATE_INT_ACK == OPT_ON
diff --git a/core/vdp_render.c b/core/vdp_render.c
index c4a1876..6b65e22 100644
--- a/core/vdp_render.c
+++ b/core/vdp_render.c
@@ -43,6 +43,14 @@
 #include "md_ntsc.h"
 #include "sms_ntsc.h"
 
+#ifndef HAVE_NO_SPRITE_LIMIT
+#define MAX_SPRITES_PER_LINE 20
+#define TMS_MAX_SPRITES_PER_LINE 4
+#define MODE4_MAX_SPRITES_PER_LINE 8
+#define MODE5_MAX_SPRITES_PER_LINE (bitmap.viewport.w >> 4)
+#define MODE5_MAX_SPRITE_PIXELS max_sprite_pixels
+#endif
+
 /*** NTSC Filters ***/
 extern md_ntsc_t *md_ntsc;
 extern sms_ntsc_t *sms_ntsc;
@@ -584,7 +592,7 @@ typedef struct
   uint16 size;
 } object_info_t;
 
-static object_info_t obj_info[2][20];
+static object_info_t obj_info[2][MAX_SPRITES_PER_LINE];
 
 /* Sprite Counter */
 static uint8 object_count[2];
@@ -3149,6 +3157,7 @@ void render_obj_m5(int line)
   int xpos, width;
   int pixelcount = 0;
   int masked = 0;
+  int max_pixels = MODE5_MAX_SPRITE_PIXELS;
 
   uint8 *src, *s, *lb;
   uint32 temp, v_line;
@@ -3213,10 +3222,10 @@ void render_obj_m5(int line)
       lb = &linebuf[0][0x20 + xpos];
 
       /* Max. number of sprite pixels rendered per line */
-      if (pixelcount > max_sprite_pixels)
+      if (pixelcount > max_pixels)
       {
         /* Adjust number of pixels to draw */
-        width -= (pixelcount - max_sprite_pixels);
+        width -= (pixelcount - max_pixels);
       }
 
       /* Number of tiles to draw */
@@ -3235,7 +3244,7 @@ void render_obj_m5(int line)
     }
 
     /* Sprite limit */
-    if (pixelcount >= max_sprite_pixels)
+    if (pixelcount >= max_pixels)
     {
       /* Sprite masking is effective on next line if max pixel width is reached */
       spr_ovr = (pixelcount >= bitmap.viewport.w);
@@ -3258,6 +3267,7 @@ void render_obj_m5_ste(int line)
   int xpos, width;
   int pixelcount = 0;
   int masked = 0;
+  int max_pixels = MODE5_MAX_SPRITE_PIXELS;
 
   uint8 *src, *s, *lb;
   uint32 temp, v_line;
@@ -3325,9 +3335,9 @@ void render_obj_m5_ste(int line)
       lb = &linebuf[1][0x20 + xpos];
 
       /* Adjust number of pixels to draw for sprite limit */
-      if (pixelcount > max_sprite_pixels)
+      if (pixelcount > max_pixels)
       {
-        width -= (pixelcount - max_sprite_pixels);
+        width -= (pixelcount - max_pixels);
       }
 
       /* Number of tiles to draw */
@@ -3346,7 +3356,7 @@ void render_obj_m5_ste(int line)
     }
 
     /* Sprite limit */
-    if (pixelcount >= max_sprite_pixels)
+    if (pixelcount >= max_pixels)
     {
       /* Sprite masking is effective on next line if max pixel width is reached */
       spr_ovr = (pixelcount >= bitmap.viewport.w);
@@ -3376,6 +3386,7 @@ void render_obj_m5_im2(int line)
   int pixelcount = 0;
   int masked = 0;
   int odd = odd_frame;
+  int max_pixels = MODE5_MAX_SPRITE_PIXELS;
 
   uint8 *src, *s, *lb;
   uint32 temp, v_line;
@@ -3440,9 +3451,9 @@ void render_obj_m5_im2(int line)
       lb = &linebuf[0][0x20 + xpos];
 
       /* Adjust width for sprite limit */
-      if (pixelcount > max_sprite_pixels)
+      if (pixelcount > max_pixels)
       {
-        width -= (pixelcount - max_sprite_pixels);
+        width -= (pixelcount - max_pixels);
       }
 
       /* Number of tiles to draw */
@@ -3461,7 +3472,7 @@ void render_obj_m5_im2(int line)
     }
 
     /* Sprite Limit */
-    if (pixelcount >= max_sprite_pixels)
+    if (pixelcount >= max_pixels)
     {
       /* Sprite masking is effective on next line if max pixel width is reached */
       spr_ovr = (pixelcount >= bitmap.viewport.w);
@@ -3485,6 +3496,7 @@ void render_obj_m5_im2_ste(int line)
   int pixelcount = 0;
   int masked = 0;
   int odd = odd_frame;
+  int max_pixels = MODE5_MAX_SPRITE_PIXELS;
 
   uint8 *src, *s, *lb;
   uint32 temp, v_line;
@@ -3552,9 +3564,9 @@ void render_obj_m5_im2_ste(int line)
       lb = &linebuf[1][0x20 + xpos];
 
       /* Adjust width for sprite limit */
-      if (pixelcount > max_sprite_pixels)
+      if (pixelcount > max_pixels)
       {
-        width -= (pixelcount - max_sprite_pixels);
+        width -= (pixelcount - max_pixels);
       }
 
       /* Number of tiles to draw */
@@ -3573,7 +3585,7 @@ void render_obj_m5_im2_ste(int line)
     }
 
     /* Sprite Limit */
-    if (pixelcount >= max_sprite_pixels)
+    if (pixelcount >= max_pixels)
     {
       /* Sprite masking is effective on next line if max pixel width is reached */
       spr_ovr = (pixelcount >= bitmap.viewport.w);
@@ -3654,7 +3666,7 @@ void parse_satb_tms(int line)
       if ((ypos >= 0) && (ypos < height))
       {
         /* Sprite overflow */
-        if (count == 4)
+        if (count == TMS_MAX_SPRITES_PER_LINE)
         {
           /* Flag is set only during active area */
           if (line < bitmap.viewport.h)
@@ -3750,7 +3762,7 @@ void parse_satb_m4(int line)
     if ((ypos >= 0) && (ypos < height))
     {
       /* Sprite overflow */
-      if (count == 8)
+      if (count == MODE4_MAX_SPRITES_PER_LINE)
       {
         /* Flag is set only during active area */
         if ((line >= 0) && (line < bitmap.viewport.h))
@@ -3796,7 +3808,7 @@ void parse_satb_m5(int line)
   int count = 0;
 
   /* max. number of rendered sprites (16 or 20 sprites per line by default) */
-  int max = bitmap.viewport.w >> 4;
+  int max = MODE5_MAX_SPRITES_PER_LINE;
 
   /* max. number of parsed sprites (64 or 80 sprites per line by default) */
   int total = max_sprite_pixels >> 2;
diff --git a/core/z80/z80.c b/core/z80/z80.c
index 59d7f4f..9a1280b 100644
--- a/core/z80/z80.c
+++ b/core/z80/z80.c
@@ -201,18 +201,15 @@
 #define IFF2 Z80.iff2
 #define HALT Z80.halt
 
-#ifdef Z80_ALLOW_OVERCLOCK
-#define USE_CYCLES(A) Z80.cycles += (A) / z80_overclock_ratio
+#ifdef Z80_OVERCLOCK_SHIFT
+#define USE_CYCLES(A) Z80.cycles += ((A) * z80_cycle_ratio) >> Z80_OVERCLOCK_SHIFT
+UINT32 z80_cycle_ratio;
 #else
 #define USE_CYCLES(A) Z80.cycles += (A)
 #endif
 
 Z80_Regs Z80;
 
-#ifdef Z80_ALLOW_OVERCLOCK
-UINT8 z80_overclock_ratio;
-#endif
-
 unsigned char *z80_readmap[64];
 unsigned char *z80_writemap[64];
 
@@ -3368,8 +3365,8 @@ void z80_init(const void *config, int (*irqcallback)(int))
   memset(&Z80, 0, sizeof(Z80));
   Z80.daisy = config;
   Z80.irq_callback = irqcallback;
-#ifdef Z80_ALLOW_OVERCLOCK
-  z80_overclock_ratio = 1;
+#ifdef Z80_OVERCLOCK_SHIFT
+  z80_cycle_ratio = 1 << Z80_OVERCLOCK_SHIFT;
 #endif
 
   /* Clear registers values (NB: should be random on real hardware ?) */
diff --git a/core/z80/z80.h b/core/z80/z80.h
index 8ee5f6b..a85f106 100644
--- a/core/z80/z80.h
+++ b/core/z80/z80.h
@@ -51,8 +51,8 @@ typedef struct
 
 extern Z80_Regs Z80;
 
-#ifdef Z80_ALLOW_OVERCLOCK
-extern UINT8 z80_overclock_ratio;
+#ifdef Z80_OVERCLOCK_SHIFT
+extern UINT32 z80_cycle_ratio;
 #endif
 
 extern unsigned char *z80_readmap[64];
diff --git a/libretro/libretro.c b/libretro/libretro.c
index c68ea21..ad07527 100644
--- a/libretro/libretro.c
+++ b/libretro/libretro.c
@@ -54,12 +54,6 @@
 #include <xtl.h>
 #endif
 
-#if defined(M68K_ALLOW_OVERCLOCK) || defined(Z80_ALLOW_OVERCLOCK)
-#define HAVE_OVERCLOCK
-/* Overclocking frame delay (hack) */
-#define OVERCLOCK_FRAME_DELAY 100
-#endif
-
 #define RETRO_DEVICE_MDPAD_3B             RETRO_DEVICE_SUBCLASS(RETRO_DEVICE_JOYPAD, 0)
 #define RETRO_DEVICE_MDPAD_6B             RETRO_DEVICE_SUBCLASS(RETRO_DEVICE_JOYPAD, 1)
 #define RETRO_DEVICE_MSPAD_2B             RETRO_DEVICE_SUBCLASS(RETRO_DEVICE_JOYPAD, 2)
@@ -82,6 +76,25 @@
 #include "sms_ntsc.h"
 #include <streams/file_stream.h>
 
+#define STATIC_ASSERT(name, test) typedef struct { int assert_[(test)?1:-1]; } assert_ ## name ## _
+#define M68K_MAX_CYCLES 1107
+#define Z80_MAX_CYCLES 345
+#define OVERCLOCK_FRAME_DELAY 100
+
+#ifdef M68K_OVERCLOCK_SHIFT
+#define HAVE_OVERCLOCK
+STATIC_ASSERT(m68k_overflow,
+              M68K_MAX_CYCLES <= UINT_MAX >> (M68K_OVERCLOCK_SHIFT + 1));
+#endif
+
+#ifdef Z80_OVERCLOCK_SHIFT
+#ifndef HAVE_OVERCLOCK
+#define HAVE_OVERCLOCK
+#endif
+STATIC_ASSERT(z80_overflow,
+              Z80_MAX_CYCLES <= UINT_MAX >> (Z80_OVERCLOCK_SHIFT + 1));
+#endif
+
 sms_ntsc_t *sms_ntsc;
 md_ntsc_t  *md_ntsc;
 
@@ -541,8 +554,9 @@ static void config_default(void)
    config.lock_on        = 0;
    config.lcd            = 0; /* 0.8 fixed point */
 #ifdef HAVE_OVERCLOCK
-   config.overclock      = 0;
+   config.overclock      = 100;
 #endif
+   config.no_sprite_limit = 0;
 
    /* video options */
    config.overscan = 0;
@@ -811,6 +825,31 @@ static bool update_viewport(void)
    return ((ow != vwidth) || (oh != vheight) || (oar != vaspect_ratio));
 }
 
+#ifdef HAVE_OVERCLOCK
+static void update_overclock(void)
+{
+#ifdef M68K_OVERCLOCK_SHIFT
+    m68k.cycle_ratio = 1 << M68K_OVERCLOCK_SHIFT;
+#endif
+#ifdef Z80_OVERCLOCK_SHIFT
+    z80_cycle_ratio = 1 << Z80_OVERCLOCK_SHIFT;
+#endif
+    if (overclock_delay == 0)
+    {
+      /* Cycle ratios multiply per-instruction cycle counts, so use
+         reciprocals */
+#ifdef M68K_OVERCLOCK_SHIFT
+      if ((system_hw & SYSTEM_PBC) == SYSTEM_MD)
+        m68k.cycle_ratio = (100 << M68K_OVERCLOCK_SHIFT) / config.overclock;
+#endif
+#ifdef Z80_OVERCLOCK_SHIFT
+      if ((system_hw & SYSTEM_PBC) != SYSTEM_MD)
+        z80_cycle_ratio = (100 << Z80_OVERCLOCK_SHIFT) / config.overclock;
+#endif
+    }
+}
+#endif
+
 static void check_variables(void)
 {
   unsigned orig_value;
@@ -1270,13 +1309,31 @@ static void check_variables(void)
   var.key = "genesis_plus_gx_overclock";
   environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var);
   {
-    if (strcmp(var.value, "1x") == 0)
-      config.overclock = 0;
-    else if (strcmp(var.value, "2x") == 0)
-      config.overclock = 1;
+    if (strcmp(var.value, "100%") == 0)
+      config.overclock = 100;
+    else if (strcmp(var.value, "125%") == 0)
+      config.overclock = 125;
+    else if (strcmp(var.value, "150%") == 0)
+      config.overclock = 150;
+    else if (strcmp(var.value, "175%") == 0)
+      config.overclock = 175;
+    else if (strcmp(var.value, "200%") == 0)
+      config.overclock = 200;
+
+    if (system_hw)
+      update_overclock();
   }
 #endif
 
+  var.key = "genesis_plus_gx_no_sprite_limit";
+  environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var);
+  {
+    if (strcmp(var.value, "disabled") == 0)
+      config.no_sprite_limit = 0;
+    else
+      config.no_sprite_limit = 1;
+  }
+
   if (reinit)
   {
 #ifdef HAVE_OVERCLOCK
@@ -1722,8 +1779,9 @@ void retro_set_environment(retro_environment_t cb)
       { "genesis_plus_gx_gun_cursor", "Show Lightgun crosshair; disabled|enabled" },
       { "genesis_plus_gx_invert_mouse", "Invert Mouse Y-axis; disabled|enabled" },
 #ifdef HAVE_OVERCLOCK
-      { "genesis_plus_gx_overclock", "Overclock CPU; 1x|2x" },
+      { "genesis_plus_gx_overclock", "CPU speed; 100%|125%|150%|175%|200%" },
 #endif
+      { "genesis_plus_gx_no_sprite_limit", "Remove per-line sprite limit; disabled|enabled" },
       { NULL, NULL },
    };
 
@@ -2069,6 +2127,7 @@ bool retro_unserialize(const void *data, size_t size)
 
 #ifdef HAVE_OVERCLOCK
    overclock_delay = OVERCLOCK_FRAME_DELAY;
+   update_overclock();
 #endif
 
    return TRUE;
@@ -2235,9 +2294,6 @@ bool retro_load_game(const struct retro_game_info *info)
       }
    }
 
-#ifdef HAVE_OVERCLOCK
-   overclock_delay = OVERCLOCK_FRAME_DELAY;
-#endif
    audio_init(SOUND_FREQUENCY, 0);
    system_init();
    system_reset();
@@ -2248,6 +2304,11 @@ bool retro_load_game(const struct retro_game_info *info)
 
    update_viewport();
 
+#ifdef HAVE_OVERCLOCK
+   overclock_delay = OVERCLOCK_FRAME_DELAY;
+   update_overclock();
+#endif
+
    return true;
 }
 
@@ -2355,6 +2416,7 @@ void retro_reset(void)
 {
 #ifdef HAVE_OVERCLOCK
    overclock_delay = OVERCLOCK_FRAME_DELAY;
+   update_overclock();
 #endif
    gen_reset(0);
 }
@@ -2366,38 +2428,20 @@ void retro_run(void)
 
 #ifdef HAVE_OVERCLOCK
   /* update overclock delay */
-  if (overclock_delay)
-      overclock_delay--;
+  if (overclock_delay && --overclock_delay == 0)
+      update_overclock();
 #endif
 
    if (system_hw == SYSTEM_MCD)
    {
-#ifdef M68K_ALLOW_OVERCLOCK
-      if (config.overclock && overclock_delay == 0)
-         m68k.overclock_ratio = 2;
-      else
-         m68k.overclock_ratio = 1;
-#endif
       system_frame_scd(0);
    }
    else if ((system_hw & SYSTEM_PBC) == SYSTEM_MD)
    {
-#ifdef M68K_ALLOW_OVERCLOCK
-      if (config.overclock && overclock_delay == 0)
-         m68k.overclock_ratio = 2;
-      else
-         m68k.overclock_ratio = 1;
-#endif
       system_frame_gen(0);
    }
    else
    {
-#ifdef Z80_ALLOW_OVERCLOCK
-      if (config.overclock && overclock_delay == 0)
-         z80_overclock_ratio = 2;
-      else
-         z80_overclock_ratio = 1;
-#endif
       system_frame_sms(0);
    }
 
diff --git a/libretro/osd.h b/libretro/osd.h
index 089bb90..f895d8b 100644
--- a/libretro/osd.h
+++ b/libretro/osd.h
@@ -76,7 +76,14 @@ typedef unsigned char bool;
 
 #define HAVE_YM3438_CORE
 
-typedef struct 
+#define HAVE_NO_SPRITE_LIMIT
+#define MAX_SPRITES_PER_LINE 80
+#define TMS_MAX_SPRITES_PER_LINE (config.no_sprite_limit ? MAX_SPRITES_PER_LINE : 4)
+#define MODE4_MAX_SPRITES_PER_LINE (config.no_sprite_limit ? MAX_SPRITES_PER_LINE : 8)
+#define MODE5_MAX_SPRITES_PER_LINE (config.no_sprite_limit ? MAX_SPRITES_PER_LINE : (bitmap.viewport.w >> 4))
+#define MODE5_MAX_SPRITE_PIXELS (config.no_sprite_limit ? MAX_SPRITES_PER_LINE * 32 : max_sprite_pixels)
+
+typedef struct
 {
   int8 device;
   uint8 port;
@@ -120,7 +127,8 @@ struct
   t_input_config input[MAX_INPUTS];
   uint8 invert_mouse;
   uint8 gun_cursor;
-  uint8 overclock;
+  uint32 overclock;
+  uint8 no_sprite_limit;
 } config;
 
 extern char GG_ROM[256];