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BIOS Reads 512mb Mem but Ubuntu/Linux, Windows Reads different

Last response: in Laptops & Notebooks
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December 26, 2011 9:12:06 PM

Hi all

This is a laptop I am trying to fix. For the longest time I thought there was a bad mem stick. Yesterday I bought new ram for it but it won't come till Friday.

So this HP laptop has 512MB (2x256) of ram installed. The BIOS will read all 512MB of memory. Windows / Ubuntu and Memtest86 read different

Ubuntu Operating System: 368.9Mb
Memtest86: 383Mb
Windows XP: I forget exactly...It was in the 300-400 range. Uninstalled Windows

I tried each mem stick individually and the BIOS reads 256Mb on each in both memory slots available. Memtest86 reads 127MB in both memory slots available.

Ubuntu froze loading probably cause there was not enough ram so I couldn't see what Ubuntu would read with 1 stick. It has a hard time running on this 368.9 that it sees.

Any idea what could cause this?

Some info from Memtest86:

With 1 256Mb stick installed
127MB - 160Mhz (DDR 320) / CAS 2.5-3-3-7 / DDR1 (64Bits)

With 2 256Mb Stick Installed (512Mb)
383Mb - 133Mhz (DDR 266) / CAS 2.5-3-3-6 / DDR1 (64Bits)

Some Laptop Specs
32 bit System
Memory Handling Capability: 1GB (2x512) DDR333 PC2700

December 26, 2011 9:19:42 PM

Some of the RAM is reserved for your video card I wager, about 125 megs.
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December 26, 2011 9:20:07 PM

Some of the memory is probably reserved for the integrated graphics, which is why operating systems don't see it.
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December 26, 2011 9:20:38 PM

Do you have a model number of the Laptop?
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a c 129 } Memory
a b D Laptop
December 26, 2011 9:32:22 PM

Windows only reports the total amount of memory available to userspace applications + shared kernel memory. Memory addresses reserved for PCI mapping (discrete VRAM), bios shadow copy (that 1MiB that always goes missing is actually a copy of the system BIOS which is aligned to the first 1MiB of address space), and RAM reserved for an integrated graphics processor are all subtracted from the amount reported. This means that 512 MiB - 1 MiB BIOS shadow - 128 MiB PCI reserved = 383 MiB remaining
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December 26, 2011 10:12:23 PM

AHhhhhhh It all comes together now. Thank you all! I was going NUTS!
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December 26, 2011 10:12:50 PM

Hey pinhedd, ur math is off, or you read the post wrong =D
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December 26, 2011 10:13:07 PM

The other questions is why would the "DDR" and memory speed change from using 1 stick to 2 sticks?
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December 26, 2011 10:15:56 PM

It might be switching from single channel to duel channel. Sometimes when ram chips come out of the factory they can't handle the full speed due to flaws, so they will scale them back at the factory.
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December 26, 2011 10:16:47 PM

Edit: Dual channel.
With an emphasis on Dual channel, I noticed one of the chips had a slightly slower CAS speed or whatever, it will be fine, unnoticeable.
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!