[people/arne_f/kernel.git] / Documentation / admin-guide / bad-memory.rst

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

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


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 admin-guide/kernel-parameters.rst 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$0x18690000
Commit	Line	Data
d078a815 MCC	1	How to deal with bad memory e.g. reported by memtest86+ ?
	2	=========================================================
	3
2884f00b PM	4	March 2008
	5	Jan-Simon Moeller, dl9pf@gmx.de
	6
	7
2884f00b PM	8
	9	There are three possibilities I know of:
	10
	11	1) Reinsert/swap the memory modules
	12
	13	2) Buy new modules (best!) or try to exchange the memory
	14	if you have spare-parts
	15
	16	3) Use BadRAM or memmap
	17
	18	This Howto is about number 3) .
	19
	20
	21	BadRAM
	22	######
d078a815	23
2884f00b PM	24	BadRAM is the actively developed and available as kernel-patch
	25	here: http://rick.vanrein.org/linux/badram/
	26
	27	For more details see the BadRAM documentation.
	28
	29	memmap
	30	######
	31
	32	memmap is already in the kernel and usable as kernel-parameter at
	33	boot-time. Its syntax is slightly strange and you may need to
	34	calculate the values by yourself!
	35
8c27ceff	36	Syntax to exclude a memory area (see admin-guide/kernel-parameters.rst for details)::
d078a815 MCC	37
d078a815 MCC	38	memmap=<size>$<address>
2884f00b PM	39
2884f00b PM	40	Example: memtest86+ reported here errors at address 0x18691458, 0x18698424 and
d078a815 MCC	41	some others. All had 0x1869xxxx in common, so I chose a pattern of
	42	0x18690000,0xffff0000.
	43
	44	With the numbers of the example above::
	45
	46	memmap=64K$0x18690000
	47
	48	or::
2884f00b	49
d078a815	50	memmap=0x10000$0x18690000