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I have a Lenovo ThinkPad T60P with 4GB of memory (BIOS sees all 4GB RAM). I have installed Ubuntu 11.04 and 11.10 and both are only recognizing 3GB RAM. Please advise.

Thanks.

Updates

Used 32bit ver for both 11.04 and 11.10. Just installed 11.10 64 bit and machine now only sees 2.9 gb.

Intel Core 2 Duo Processor T7600

ThinkPad-T60p:~$ uname -a Linux ThinkPad-T60p 3.0.0-14-generic
 #23-Ubuntu SMP Mon Nov 21 20:28:43 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux



flags: fpu vme de pse tsc msr PAE mce cx8 apic  etc, etc...  

4GB of Crucial RAM, memory test Passed. Current BIOS is 2.27 dated 3/21/11

Sending memory back to vendor for replacement. Hope that takes care of it.

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Are you using 32 bit os or 64 bit os ? I recommend you to install 64bit ubuntu if you are using 32bit. –  sagarchalise Dec 27 '11 at 5:03
    
I am assuming that you are using 32bit Ubuntu. 32bit OS has address space limitation, which causes it to access only 3Gb of RAM. You can access 4GB of your ram in 32bit OS by activating PAE. But, why take so much headache, just install 64bit Ubuntu. –  Abhijeet Dec 27 '11 at 10:15
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2 Answers 2

32 bit Ubuntu should detect > 4GB RAM at install and 'automagically' enable Physical Address Extensions, which lets you use up to 64GB RAM. Not in exactly the same way as 64 bit installs, but you can see it and use it. Check that your processor supports this first:

grep --color=always -i PAE /proc/cpuinfo  

I had this same laptop (excellent machine, btw) with 4GB RAM and this all worked just fine.

Failing that, you can test your memory to make sure it is not the culprit here. You need to choose memtest86 at the GRUB menu. You can do this from the Live CD or USB if you have just one OS installed and don't usually see GRUB at boot.

If none of this helps, post an update to your question with more info and we can help you some more.

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Used 32bit ver for both 11.04 and 11.10. Just installed 11.10 64 bit and machine now only sees 2.9 gb. –  user39440 Dec 28 '11 at 1:54
    
processor is ark.intel.com/products/27257/… –  user39440 Dec 28 '11 at 1:57
    
ThinkPad-T60p:~$ uname -a Linux ThinkPad-T60p 3.0.0-14-generic #23-Ubuntu SMP Mon Nov 21 20:28:43 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux –  user39440 Dec 28 '11 at 3:38
    
flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good nopl aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm lahf_lm dts tpr_shadow flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good nopl aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm lahf_lm dts tpr_shadow –  user39440 Dec 28 '11 at 3:42
    
From your fourth comment I can see that your processor is capable of handling PAE, so that's not the issue here. Have you tried the memory test? Even if your memory has gone bad you can replace it pretty cheaply and get several more years out of the machine. Lastly, see if you have the most current BIOS. Version 2.27 from April '11 is current, you need to use a Bootable CD unless you still have Windows on a partition. More here: support.lenovo.com/en_US/downloads/… –  Tom Brossman Dec 28 '11 at 9:13
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Refer to http://support.lenovo.com/en_US/product-and-parts/detail.page?DocID=PD008795

The note on MEMORY paragraph explains what chipsets only recognize 3GB even if the laptop has 4GB installed.

Then the OS needs to be 64bit in order to have the full 4GB available on the laptop whose chipset will support that memory size.

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-1 This is wrong. Your linked document is applicable only to Windows. 32-bit Ubuntu automatically detects and enables PAE at install, seeing up to 64GB RAM. This has been the case since 10.04. See here for details: help.ubuntu.com/community/EnablingPAE –  Tom Brossman Jan 23 '12 at 8:45
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