diff -Naur burg.orig//include/grub/disk.h burg.patch//include/grub/disk.h
--- burg.orig//include/grub/disk.h	2011-03-08 23:30:19.033192285 +0100
+++ burg.patch//include/grub/disk.h	2011-03-08 23:29:30.153195171 +0100
@@ -138,8 +138,8 @@
 #define GRUB_DISK_CACHE_NUM	1021
 
 /* The size of a disk cache in sector units.  */
-#define GRUB_DISK_CACHE_SIZE	8
-#define GRUB_DISK_CACHE_BITS	3
+#define GRUB_DISK_CACHE_SIZE	32 /*8*/
+#define GRUB_DISK_CACHE_BITS	5  /*3*/
 
 /* This is called from the memory manager.  */
 void grub_disk_cache_invalidate_all (void);
diff -Naur burg.orig//kern/disk.c burg.patch//kern/disk.c
--- burg.orig//kern/disk.c	2011-03-08 23:29:45.113192284 +0100
+++ burg.patch//kern/disk.c	2011-03-08 23:34:35.283192206 +0100
@@ -408,6 +408,17 @@
 {
   char *tmp_buf;
   unsigned real_offset;
+  grub_size_t read_size = GRUB_DISK_CACHE_SIZE;
+  grub_size_t read_bits = GRUB_DISK_CACHE_BITS;
+
+  char use_cache = 1;
+  /* disable cache for huge files (>1MB) */
+  if (size > 0x100000)
+    {
+      use_cache = 0;
+      read_size = GRUB_DISK_SECTOR_SIZE;
+      read_bits = GRUB_DISK_SECTOR_BITS;
+    }
 
   /* First of all, check if the region is within the disk.  */
   if (grub_disk_adjust_range (disk, &sector, &offset, size) != GRUB_ERR_NONE)
@@ -422,14 +433,14 @@
   real_offset = offset;
 
   /* Allocate a temporary buffer.  */
-  tmp_buf = grub_malloc (GRUB_DISK_SECTOR_SIZE << GRUB_DISK_CACHE_BITS);
+  tmp_buf = grub_malloc (GRUB_DISK_SECTOR_SIZE << read_bits);
   if (! tmp_buf)
     return grub_errno;
 
   /* Until SIZE is zero...  */
   while (size)
     {
-      char *data;
+      char *data = NULL;
       grub_disk_addr_t start_sector;
       grub_size_t len;
       grub_size_t pos;
@@ -437,13 +448,14 @@
       /* For reading bulk data.  */
       start_sector = sector & ~(GRUB_DISK_CACHE_SIZE - 1);
       pos = (sector - start_sector) << GRUB_DISK_SECTOR_BITS;
-      len = ((GRUB_DISK_SECTOR_SIZE << GRUB_DISK_CACHE_BITS)
+      len = ((GRUB_DISK_SECTOR_SIZE << read_bits)
 	     - pos - real_offset);
       if (len > size)
 	len = size;
 
       /* Fetch the cache.  */
-      data = grub_disk_cache_fetch (disk->dev->id, disk->id, start_sector);
+      if (use_cache)
+        data = grub_disk_cache_fetch (disk->dev->id, disk->id, start_sector);
       if (data)
 	{
 	  /* Just copy it!  */
@@ -453,9 +465,9 @@
       else
 	{
 	  /* Otherwise read data from the disk actually.  */
-	  if (start_sector + GRUB_DISK_CACHE_SIZE > disk->total_sectors
+	  if (start_sector + read_size > disk->total_sectors
 	      || (disk->dev->read) (disk, start_sector,
-				    GRUB_DISK_CACHE_SIZE, tmp_buf)
+				    read_size, tmp_buf)
 	      != GRUB_ERR_NONE)
 	    {
 	      /* Uggh... Failed. Instead, just read necessary data.  */
@@ -508,7 +520,8 @@
 
 	  /* Copy it and store it in the disk cache.  */
 	  grub_memcpy (buf, tmp_buf + pos + real_offset, len);
-	  grub_disk_cache_store (disk->dev->id, disk->id,
+	  if (use_cache)
+	    grub_disk_cache_store (disk->dev->id, disk->id,
 				 start_sector, tmp_buf);
 	}
 
@@ -534,7 +547,7 @@
 	    }
 	}
 
-      sector = start_sector + GRUB_DISK_CACHE_SIZE;
+      sector = start_sector + read_size;
       buf = (char *) buf + len;
       size -= len;
       real_offset = 0;