[deliverable/linux.git] / Documentation / bad_memory.txt

March 2008
Jan-Simon Moeller, dl9pf@gmx.de


How to deal with bad memory e.g. reported by memtest86+ ?
#########################################################

There are three possibilities I know of:

1) Reinsert/swap the memory modules

2) Buy new modules (best!) or try to exchange the memory
   if you have spare-parts

3) Use BadRAM or memmap

This Howto is about number 3) .


BadRAM
######
BadRAM is the actively developed and available as kernel-patch
here:  http://rick.vanrein.org/linux/badram/

For more details see the BadRAM documentation.

memmap
######

memmap is already in the kernel and usable as kernel-parameter at
boot-time.  Its syntax is slightly strange and you may need to
calculate the values by yourself!

Syntax to exclude a memory area (see kernel-parameters.txt for details):
memmap=<size>$<address>

Example: memtest86+ reported here errors at address 0x18691458, 0x18698424 and
         some others. All had 0x1869xxxx in common, so I chose a pattern of
         0x18690000,0xffff0000.

With the numbers of the example above:
memmap=64K$0x18690000
 or
memmap=0x10000$0x18690000
Commit	Line	Data
2884f00b PM	1	March 2008
	2	Jan-Simon Moeller, dl9pf@gmx.de
	3
	4
	5	How to deal with bad memory e.g. reported by memtest86+ ?
	6	#########################################################
	7
	8	There are three possibilities I know of:
	9
	10	1) Reinsert/swap the memory modules
	11
	12	2) Buy new modules (best!) or try to exchange the memory
	13	if you have spare-parts
	14
	15	3) Use BadRAM or memmap
	16
	17	This Howto is about number 3) .
	18
	19
	20	BadRAM
	21	######
	22	BadRAM is the actively developed and available as kernel-patch
	23	here: http://rick.vanrein.org/linux/badram/
	24
	25	For more details see the BadRAM documentation.
	26
	27	memmap
	28	######
	29
	30	memmap is already in the kernel and usable as kernel-parameter at
	31	boot-time. Its syntax is slightly strange and you may need to
	32	calculate the values by yourself!
	33
	34	Syntax to exclude a memory area (see kernel-parameters.txt for details):
	35	memmap=<size>$<address>
	36
	37	Example: memtest86+ reported here errors at address 0x18691458, 0x18698424 and
	38	some others. All had 0x1869xxxx in common, so I chose a pattern of
	39	0x18690000,0xffff0000.
	40
	41	With the numbers of the example above:
	42	memmap=64K$0x18690000
	43	or
	44	memmap=0x10000$0x18690000
	45