diff -urNp x-ref/drivers/ide/ide-probe.c x/drivers/ide/ide-probe.c
--- x-ref/drivers/ide/ide-probe.c	2002-12-11 02:12:21.000000000 +0100
+++ x/drivers/ide/ide-probe.c	2002-12-13 03:43:15.000000000 +0100
@@ -1008,7 +1008,10 @@ static void init_gendisk (ide_hwif_t *hw
 		 * IDE can do up to 128K per request == 256
 		 */
 		*max_sect++ = ((hwif->rqsize) ? hwif->rqsize : 128);
-		*max_ra++ = vm_max_readahead;
+		*max_ra = ((128*4) >> (PAGE_SHIFT - 10)) - 1; /* sequential read with 4 requests 128k large DMA */
+		if (hwif->chipset == ide_pdc4030)
+			*max_ra = ((127*4) >> (PAGE_SHIFT - 10)) - 1; /* sequential read with 4 requests 127k large DMA */
+		max_ra++;
 	}
 
 	for (unit = 0; unit < units; ++unit)
diff -urNp x-ref/mm/filemap.c x/mm/filemap.c
--- x-ref/mm/filemap.c	2002-12-13 03:42:31.000000000 +0100
+++ x/mm/filemap.c	2002-12-13 03:42:34.000000000 +0100
@@ -46,7 +46,7 @@ atomic_t page_cache_size = ATOMIC_INIT(0
 unsigned int page_hash_bits;
 struct page **page_hash_table;
 
-int vm_max_readahead = 31;
+int vm_max_readahead = (512 >> (PAGE_SHIFT - 10)) - 1; /* sequential read 512k large DMA */
 int vm_min_readahead = 3;
 EXPORT_SYMBOL(vm_max_readahead);
 EXPORT_SYMBOL(vm_min_readahead);