Contents of /alx-src/tags/kernel26-2.6.12-alx-r9/Documentation/memory.txt
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Wed Mar 4 11:03:09 2009 UTC (15 years, 3 months ago) by niro
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Wed Mar 4 11:03:09 2009 UTC (15 years, 3 months ago) by niro
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File size: 2177 byte(s)
Tag kernel26-2.6.12-alx-r9
1 | There are several classic problems related to memory on Linux |
2 | systems. |
3 | |
4 | 1) There are some buggy motherboards which cannot properly |
5 | deal with the memory above 16MB. Consider exchanging |
6 | your motherboard. |
7 | |
8 | 2) You cannot do DMA on the ISA bus to addresses above |
9 | 16M. Most device drivers under Linux allow the use |
10 | of bounce buffers which work around this problem. Drivers |
11 | that don't use bounce buffers will be unstable with |
12 | more than 16M installed. Drivers that use bounce buffers |
13 | will be OK, but may have slightly higher overhead. |
14 | |
15 | 3) There are some motherboards that will not cache above |
16 | a certain quantity of memory. If you have one of these |
17 | motherboards, your system will be SLOWER, not faster |
18 | as you add more memory. Consider exchanging your |
19 | motherboard. |
20 | |
21 | All of these problems can be addressed with the "mem=XXXM" boot option |
22 | (where XXX is the size of RAM to use in megabytes). |
23 | It can also tell Linux to use less memory than is actually installed. |
24 | If you use "mem=" on a machine with PCI, consider using "memmap=" to avoid |
25 | physical address space collisions. |
26 | |
27 | See the documentation of your boot loader (LILO, loadlin, etc.) about |
28 | how to pass options to the kernel. |
29 | |
30 | There are other memory problems which Linux cannot deal with. Random |
31 | corruption of memory is usually a sign of serious hardware trouble. |
32 | Try: |
33 | |
34 | * Reducing memory settings in the BIOS to the most conservative |
35 | timings. |
36 | |
37 | * Adding a cooling fan. |
38 | |
39 | * Not overclocking your CPU. |
40 | |
41 | * Having the memory tested in a memory tester or exchanged |
42 | with the vendor. Consider testing it with memtest86 yourself. |
43 | |
44 | * Exchanging your CPU, cache, or motherboard for one that works. |
45 | |
46 | * Disabling the cache from the BIOS. |
47 | |
48 | * Try passing the "mem=4M" option to the kernel to limit |
49 | Linux to using a very small amount of memory. Use "memmap="-option |
50 | together with "mem=" on systems with PCI to avoid physical address |
51 | space collisions. |
52 | |
53 | |
54 | Other tricks: |
55 | |
56 | * Try passing the "no-387" option to the kernel to ignore |
57 | a buggy FPU. |
58 | |
59 | * Try passing the "no-hlt" option to disable the potentially |
60 | buggy HLT instruction in your CPU. |