diff --git a/BasiliskII/TODO b/BasiliskII/TODO
index 35abe34f..c1f05aa2 100644
--- a/BasiliskII/TODO
+++ b/BasiliskII/TODO
@@ -16,6 +16,8 @@ General:
 - Classic ROM: mouse button/movement is broken with ROM mouse handler
 - Classic ROM: sound output
 - Write a nice User's Manual with linuxdoc or something similar
+- Fix video mode switch to cope with different mac_frame_base
+  (CrsrBase is overriden with the previous base after the mode switch)
 
 AmigaOS:
 - "Create Hardfile..." button
diff --git a/BasiliskII/src/SDL/video_sdl.cpp b/BasiliskII/src/SDL/video_sdl.cpp
index 5d9d3f4d..a527609b 100644
--- a/BasiliskII/src/SDL/video_sdl.cpp
+++ b/BasiliskII/src/SDL/video_sdl.cpp
@@ -197,7 +197,19 @@ extern void SysMountFirstFloppy(void);
 
 static void *vm_acquire_framebuffer(uint32 size)
 {
-	return vm_acquire(size);
+	// always try to reallocate framebuffer at the same address
+	static void *fb = VM_MAP_FAILED;
+	if (fb != VM_MAP_FAILED) {
+		if (vm_acquire_fixed(fb, size) < 0) {
+#ifndef SHEEPSHAVER
+			printf("FATAL: Could not reallocate framebuffer at previous address\n");
+#endif
+			fb = VM_MAP_FAILED;
+		}
+	}
+	if (fb == VM_MAP_FAILED)
+		fb = vm_acquire(size, VM_MAP_DEFAULT | VM_MAP_32BIT);
+	return fb;
 }
 
 static inline void vm_release_framebuffer(void *fb, uint32 size)
@@ -719,7 +731,7 @@ void driver_base::restore_mouse_accel(void)
  *  Windowed display driver
  */
 
-static int SDL_display_opened = FALSE;
+static bool SDL_display_opened = false;
 
 // Open display
 driver_window::driver_window(SDL_monitor_desc &m)
@@ -747,7 +759,7 @@ driver_window::driver_window(SDL_monitor_desc &m)
 	if ((s = SDL_SetVideoMode(width, height, depth, SDL_HWSURFACE)) == NULL)
 		return;
 
-	SDL_display_opened = TRUE;
+	SDL_display_opened = true;
 
 #ifdef ENABLE_VOSF
 	use_vosf = true;
diff --git a/BasiliskII/src/Unix/video_x.cpp b/BasiliskII/src/Unix/video_x.cpp
index f2371a9f..9e4a9b1d 100644
--- a/BasiliskII/src/Unix/video_x.cpp
+++ b/BasiliskII/src/Unix/video_x.cpp
@@ -194,7 +194,6 @@ static void *redraw_func(void *arg);
 // From main_unix.cpp
 extern char *x_display_name;
 extern Display *x_display;
-extern void *vm_acquire_mac(size_t size);
 
 // From sys_unix.cpp
 extern void SysMountFirstFloppy(void);
@@ -497,6 +496,33 @@ static int error_handler(Display *d, XErrorEvent *e)
 }
 
 
+/*
+ *  Framebuffer allocation routines
+ */
+
+#ifdef ENABLE_VOSF
+#include "vm_alloc.h"
+
+static void *vm_acquire_framebuffer(uint32 size)
+{
+	// always try to allocate framebuffer at the same address
+	static void *fb = VM_MAP_FAILED;
+	if (fb != VM_MAP_FAILED) {
+		if (vm_acquire_fixed(fb, size) < 0)
+			fb = VM_MAP_FAILED;
+	}
+	if (fb == VM_MAP_FAILED)
+		fb = vm_acquire(size, VM_MAP_DEFAULT | VM_MAP_32BIT);
+	return fb;
+}
+
+static inline void vm_release_framebuffer(void *fb, uint32 size)
+{
+	vm_release(fb, size);
+}
+#endif
+
+
 /*
  *  Display "driver" classes
  */
@@ -632,7 +658,7 @@ driver_base::~driver_base()
 		// the_buffer shall always be mapped through vm_acquire() so that we can vm_protect() it at will
 		if (the_buffer != VM_MAP_FAILED) {
 			D(bug(" releasing the_buffer at %p (%d bytes)\n", the_buffer, the_buffer_size));
-			vm_release(the_buffer, the_buffer_size);
+			vm_release_framebuffer(the_buffer, the_buffer_size);
 			the_buffer = NULL;
 		}
 		if (the_host_buffer) {
@@ -782,7 +808,7 @@ driver_window::driver_window(X11_monitor_desc &m)
 	// Allocate memory for frame buffer (SIZE is extended to page-boundary)
 	the_host_buffer = the_buffer_copy;
 	the_buffer_size = page_extend((aligned_height + 2) * img->bytes_per_line);
-	the_buffer = (uint8 *)vm_acquire_mac(the_buffer_size);
+	the_buffer = (uint8 *)vm_acquire_framebuffer(the_buffer_size);
 	the_buffer_copy = (uint8 *)malloc(the_buffer_size);
 	D(bug("the_buffer = %p, the_buffer_copy = %p, the_host_buffer = %p\n", the_buffer, the_buffer_copy, the_host_buffer));
 #else
@@ -1162,7 +1188,7 @@ driver_fbdev::driver_fbdev(X11_monitor_desc &m) : driver_dga(m)
 	  the_host_buffer = the_buffer;
 	  the_buffer_size = page_extend((height + 2) * bytes_per_row);
 	  the_buffer_copy = (uint8 *)malloc(the_buffer_size);
-	  the_buffer = (uint8 *)vm_acquire_mac(the_buffer_size);
+	  the_buffer = (uint8 *)vm_acquire_framebuffer(the_buffer_size);
 
 	  // Fake image for DGA/VOSF mode to know about display bounds
 	  img = new FakeXImage(width, height, depth_of_video_mode(mode));
@@ -1299,7 +1325,7 @@ driver_xf86dga::driver_xf86dga(X11_monitor_desc &m)
 	  the_host_buffer = the_buffer;
 	  the_buffer_size = page_extend((height + 2) * bytes_per_row);
 	  the_buffer_copy = (uint8 *)malloc(the_buffer_size);
-	  the_buffer = (uint8 *)vm_acquire_mac(the_buffer_size);
+	  the_buffer = (uint8 *)vm_acquire_framebuffer(the_buffer_size);
 
 	  // Fake image for DGA/VOSF mode to know about display bounds
 	  img = new FakeXImage((v_width + 7) & ~7, height, depth_of_video_mode(mode));