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Im using linux mint (ubuntu based, kernel exactly the same), The problem also occurs on Ubuntu
My computer is a HP dv1220us laptop:
512MB DDR SDRAM (2 x 256MB) at 266MHz
Intel Centrino 1.5GHz Processor
Intel Graphics Card
Shared 64mb Video Memory
Half the time i boot linux, I find that the system has only detected 256mb of ram. I know I have 512mb of ram, and that is what windows detects. Also, the other half of the time linux detects my ram correctly.
This is very annoying and I cant think of any reason why it would sometimes fail to detect half my memory. I do have 2x 256mb sticks in my laptop, could one of those be going bad?
I think this is probably a problem with grub, I belive it is the system which detects the available ram and instructs the kernel how much is available. Correct?
This theory holds as grub does not directly load Windows, it chainloads it. Therefor Windows would not be affected by grubs bad detection of available ram.
But why would it detect it correctly half the time, and incorrectly the other half. I cannot find anything im doing that seems to relate to when the memory is detected correctly.
I have tried adding "mem=512m" to the kernel params in grub, however doing so causes grub to fail to load the kernel saying something like "object will not fit in ram" (i think)
Thanks For your help this problem has really stumped me
Do you have two different brands or speeds of memory in that machine? I believe that memory is normally detected by BIOS. Are you sure that the BIOS is displaying the correct amount of memory on those occasions where Linux doesn't sense it properly?
thanks for the reply, the memory in the pc is the same, in fact, i havent changed it since i bought the pc. Ill check the bios later as i dont have access to that pc atm. I'm doutfull that it is a hardware problem as windows allways shows 512mb and it only sometimes fails to show it all on linux.
Linux actually uses all the memory all the time (one way or another). Windows just lets it set if it does not use it. If the memory is having an intermittent failure windows may not detect it, but Linux will. I would run memtest86+ on it for at least a couple of hours (the version that uses a boot disk). If that comes back clean then it may be a Linux problem, but 99% of the time it is a hardware issue.
How long did you run memtest? It needs to be ran for at LEAST a couple of hours. Many times the errors will not show up until the memory get warmed up.
The bios and windows only check the memory at startup.
it really doesnt seem like a memory problem. Browsing the forums there seem a few threads stating that linux detected half their memory, but none of them have been solved.
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