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[tlug] Memory upgrade and CPU bit-width question

Hi all,

I have a question for you which cannot be easily answered by googling,

I have a 2009 vintage Thinkpad X61 convertible tablet laptop (which I
have never used as a tablet and probably never will :=)  A while ago I
upped the RAM to 3GB and it's been quite usable that way. A few weeks
ago I looked up its memory type and found a really cheap stick that
would take me to 4GB, and since I plan on continuing to use the thing a
while longer, I thought this was a good investment (also going to SSD!)

Problem is, I didn't do the homework, just assumed it would be fine, and
when the new RAM was not fully recognized, I googled and found that
there is a hard limit for 32-bit machines to 3GB, even though this
machine is said to support 4GB. (The BIOS does report 4GB inserted).

Long story short, I tried a few tricks that didn't work, but also in
the process of investigating this, found that my CPU (Core 2 Duo
L7500) is actually a 64-bit CPU! Sooooooo..... in theory I could
configure my kernel (3.14.56) as 64-bit, and then perhaps rebuild my
userland as appropriate (it's Gentoo), and then my extra 1GB would be
usable.... maybe?

But I also found this cool new tool called lshw, which tells me some
interesting things about my hardware components, which is that although
the CPU cores are technically 64-bit wide, my "memory controller hub",
"PCI bridge", and other things are only 32. The whole thing looks to be
a random hodgepodge of 32 and 64 bit wide components :=\

Will I be wasting my time to go through a lot of gyrations to configure
my OS as 64-bit, because it just won't help in the end anyway?  Might
even make the box slower?  Seems I might be able to use that 2GB stick I
bought to upgrade a Macbook my wife uses (same era, and I think same CPU
family) to 3GB, so maybe the purchase was not in vain :=)



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