diff --git a/library/changes b/library/changes
index b010975..9037cd4 100644
--- a/library/changes
+++ b/library/changes
@@ -1,3 +1,6 @@
+- I/O buffers allocated are now aligned according to the CPU cache line size,
+  if the operating system can supply that detailed information.
+
 - unsetenv() now returns a status value.
 
 - Corrected the function prototype for wcspbrk().
diff --git a/library/stdio_file_init.c b/library/stdio_file_init.c
index 5f5a5fc..8e51c56 100644
--- a/library/stdio_file_init.c
+++ b/library/stdio_file_init.c
@@ -1,5 +1,5 @@
 /*
- * $Id: stdio_file_init.c,v 1.12 2006-11-16 14:39:23 obarthel Exp $
+ * $Id: stdio_file_init.c,v 1.13 2008-09-04 12:07:58 obarthel Exp $
  *
  * :ts=4
  *
@@ -76,6 +76,11 @@ struct WBStartup * NOCOMMON __WBenchMsg;
 
 /****************************************************************************/
 
+/* CPU cache line size; used to align I/O buffers for best performance. */
+ULONG __cache_line_size = 32;
+
+/****************************************************************************/
+
 FILE_DESTRUCTOR(workbench_exit)
 {
 	ENTER();
@@ -215,6 +220,24 @@ FILE_CONSTRUCTOR(stdio_file_init)
 
 	ENTER();
 
+	/* Figure out the proper address alignment for the memory we are
+	   going to use for disk I/O. The default is 32 bytes, which should
+	   be OK for most cases. If possible, ask the operating system for
+	   its preferred alignment size. */
+	#if defined(__amigaos4__)
+	{
+		if(SysBase->lib_Version >= 50)
+		{
+			uint32 physical_alignment = 0;
+
+			GetCPUInfoTags(GCIT_CacheLineSize,&physical_alignment,TAG_DONE);
+
+			if(__cache_line_size < physical_alignment)
+				__cache_line_size = physical_alignment;
+		}
+	}
+	#endif /* __amigaos4__ */
+
 	/* If we were invoked from Workbench, set up the standard I/O streams. */
 	if(__WBenchMsg != NULL)
 	{
@@ -255,7 +278,7 @@ FILE_CONSTRUCTOR(stdio_file_init)
 		PROFILE_ON();
 
 		/* Allocate a little more memory than necessary. */
-		buffer = malloc(BUFSIZ + (CACHE_LINE_SIZE-1));
+		buffer = malloc(BUFSIZ + (__cache_line_size - 1));
 		if(buffer == NULL)
 			goto out;
 
@@ -300,7 +323,7 @@ FILE_CONSTRUCTOR(stdio_file_init)
 		#endif /* __THREAD_SAFE */
 
 		/* Align the buffer start address to a cache line boundary. */
-		aligned_buffer = (char *)((ULONG)(buffer + (CACHE_LINE_SIZE-1)) & ~(CACHE_LINE_SIZE-1));
+		aligned_buffer = (char *)((ULONG)(buffer + (__cache_line_size-1)) & ~(__cache_line_size-1));
 
 		__initialize_fd(__fd[i],__fd_hook_entry,default_file,fd_flags,fd_lock);
 
diff --git a/library/stdio_grow_file.c b/library/stdio_grow_file.c
index 1f45623..2a3eedd 100644
--- a/library/stdio_grow_file.c
+++ b/library/stdio_grow_file.c
@@ -1,5 +1,5 @@
 /*
- * $Id: stdio_grow_file.c,v 1.7 2006-11-16 14:39:23 obarthel Exp $
+ * $Id: stdio_grow_file.c,v 1.8 2008-09-04 12:07:58 obarthel Exp $
  *
  * :ts=4
  *
@@ -90,7 +90,7 @@ __grow_file_size(struct fd * fd,int num_bytes)
 	/* Allocate a little more memory than required to allow for
 	 * the buffer to be aligned to a cache line boundary.
 	 */
-	buffer = malloc((size_t)buffer_size + (CACHE_LINE_SIZE-1));
+	buffer = malloc((size_t)buffer_size + (__cache_line_size-1));
 	if(buffer == NULL)
 	{
 		SHOWMSG("not enough memory for write buffer");
@@ -100,7 +100,7 @@ __grow_file_size(struct fd * fd,int num_bytes)
 	}
 
 	/* Align the buffer to a cache line boundary. */
-	aligned_buffer = (unsigned char *)(((ULONG)(buffer + (CACHE_LINE_SIZE-1))) & ~(CACHE_LINE_SIZE-1));
+	aligned_buffer = (unsigned char *)(((ULONG)(buffer + (__cache_line_size-1))) & ~(__cache_line_size-1));
 
 	memset(aligned_buffer,0,(size_t)buffer_size);
 
diff --git a/library/stdio_headers.h b/library/stdio_headers.h
index c836059..df1e7a1 100644
--- a/library/stdio_headers.h
+++ b/library/stdio_headers.h
@@ -1,5 +1,5 @@
 /*
- * $Id: stdio_headers.h,v 1.30 2006-11-16 14:39:23 obarthel Exp $
+ * $Id: stdio_headers.h,v 1.31 2008-09-04 12:07:58 obarthel Exp $
  *
  * :ts=4
  *
@@ -156,18 +156,6 @@ struct iob;
 
 /****************************************************************************/
 
-/* CPU cache line size; used for alignment purposes with some data structures.
-   This should be determined dynamically rather than preset here. For the
-   68040/68060 the cache line size is 16 bytes, for the PowerPC G4 it's
-   32 bytes and 128 bytes (gross!) for the PowerPC G5. */
-#if defined(__PPC__)
-#define CACHE_LINE_SIZE 32UL
-#else
-#define CACHE_LINE_SIZE 16UL
-#endif /* __PPC__ */
-
-/****************************************************************************/
-
 /* The directory entry type a socket is identified with (in a FileInfoBlock). */
 #define ST_SOCKET (31082002)
 
@@ -399,6 +387,11 @@ extern BOOL NOCOMMON __no_standard_io;
 
 /****************************************************************************/
 
+/* CPU cache line size; used to align I/O buffers for best performance. */
+extern ULONG __cache_line_size;
+
+/****************************************************************************/
+
 /*extern int __iob_write_buffer_is_full(struct iob * file);*/
 
 #define __iob_write_buffer_is_full(file) \
diff --git a/library/stdio_openiob.c b/library/stdio_openiob.c
index 19c7c82..ec5e5f2 100644
--- a/library/stdio_openiob.c
+++ b/library/stdio_openiob.c
@@ -1,5 +1,5 @@
 /*
- * $Id: stdio_openiob.c,v 1.14 2006-01-08 12:04:24 obarthel Exp $
+ * $Id: stdio_openiob.c,v 1.15 2008-09-04 12:07:58 obarthel Exp $
  *
  * :ts=4
  *
@@ -133,7 +133,7 @@ __open_iob(const char *filename, const char *mode, int file_descriptor, int slot
 	SHOWMSG("allocating file buffer");
 
 	/* Allocate a little more memory than necessary. */
-	buffer = malloc(BUFSIZ + (CACHE_LINE_SIZE-1));
+	buffer = malloc(BUFSIZ + (__cache_line_size-1));
 	if(buffer == NULL)
 	{
 		SHOWMSG("that didn't work");
@@ -143,7 +143,7 @@ __open_iob(const char *filename, const char *mode, int file_descriptor, int slot
 	}
 
 	/* Align the buffer start address to a cache line boundary. */
-	aligned_buffer = (char *)((ULONG)(buffer + (CACHE_LINE_SIZE-1)) & ~(CACHE_LINE_SIZE-1));
+	aligned_buffer = (char *)((ULONG)(buffer + (__cache_line_size-1)) & ~(__cache_line_size-1));
 
 	if(file_descriptor < 0)
 	{
diff --git a/library/stdio_setvbuf.c b/library/stdio_setvbuf.c
index c8afaaf..785fdbb 100644
--- a/library/stdio_setvbuf.c
+++ b/library/stdio_setvbuf.c
@@ -1,5 +1,5 @@
 /*
- * $Id: stdio_setvbuf.c,v 1.10 2006-09-22 09:02:51 obarthel Exp $
+ * $Id: stdio_setvbuf.c,v 1.11 2008-09-04 12:07:58 obarthel Exp $
  *
  * :ts=4
  *
@@ -123,7 +123,7 @@ setvbuf(FILE *stream,char *buf,int bufmode,size_t size)
 	if(size > 0 && buf == NULL)
 	{
 		/* Allocate a little more memory than necessary. */
-		new_buffer = malloc(size + (CACHE_LINE_SIZE-1));
+		new_buffer = malloc(size + (__cache_line_size-1));
 		if(new_buffer == NULL)
 		{
 			__set_errno(ENOBUFS);
@@ -170,7 +170,7 @@ setvbuf(FILE *stream,char *buf,int bufmode,size_t size)
 			file->iob_CustomBuffer = new_buffer;
 
 			/* Align the buffer start address to a cache line boundary. */
-			new_buffer = (char *)((ULONG)(new_buffer + (CACHE_LINE_SIZE-1)) & ~(CACHE_LINE_SIZE-1));
+			new_buffer = (char *)((ULONG)(new_buffer + (__cache_line_size-1)) & ~(__cache_line_size-1));
 		}
 	}