Miscellaneous > Technical Support
13.4MB of memory is missing!
Aloone_Jonez:
I've just upgraded to 512MB but Linux is only reporting 490.6MB.
I know I have an on board video adaptor which is configured to use 8MB which makes 504MB, so where's the remaining 13.4MB?
I know that this is an OS problem, not a BIOS or hardware problem because Windows reports 504MB.
I've tried removing one of the RAM modules and I still get the same problem so the upgrade isn't the problem, it's just what's caused me to notice it.
I know 13.4MB of memory isn't much, it would just be nice to know what's happened to it.
davidnix71:
Bit and bytes, maybe. 512 divided by 1.024 equals exactly 500.
Maybe your ram is off-spec and the flavor of Linux you use does a ram check at boot and only found 490.6.
Aloone_Jonez:
I know it isn't the RAM module because the amount of memory is reported correctly by Windows and the BIOS.
As far as the rounding error is concerned: I don't see why it should be rounded like that. As far as I'm aware, RAM is normally specified in MiB, i.e. 1MiB = 1024KiB = 1,048,576 bytes, so to be pedantic I really have 536.9MB but 8.38MB is being used for video so it should report 528.5MB (more) not 490.6MB (less).
EDIT:
Even GRUB seems to be reporting the amount of memory correctly, 639KiB of conventional + 515,008KiB of extended memory which works out at 503.56MiB and is probably a rounding error.
davidnix71:
If your ram maker lied like hard drive makers did before they got sued, then 512 million bites would be 488.28 MB
(512 divided by 1.048576)
If you read the fine print on some hard drives, the number may be "one terabyte" meaning 1 trillion bites (which is a lie, of course), but that's actually the minimum number of good sectors they will ship the drive with. The real number is always a little larger than that. When that ram module was made, it could have came in at 514.4 million bites or so, which is really 490.6 MB
Your ram module firmware may report it's size to Windows in a rounded fashion "I'm a 512MB DDR2-444 SO-DIMM module", but that's not the real usuable number.
I would trust Linux to check the real usable number and pass that on to you.
Aloone_Jonez:
But the BIOS memory check actually scans the memory at boot up and reports the memory in KB which I divided by 1024 to give exactly 504MB of RAM.
I doubt the hard drive companies were actually sued because they were right, the International Standard System of Units lists 1MB as 1,000,000 bytes not 1,048,576 bytes which is really 1MiB.
http://en.wikipedia.org/wiki/Megabyte
http://en.wikipedia.org/wiki/Binary_prefix
I think more investigation is required, I'll try removing one of the of the modules and see if the amount of RAM missing stays the same, if it does then I'll replace the module and remove the other, to check they're both the same capacity.
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