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[archive] When I'm 64 in Acucorp News

[Migrated content. Thread originally posted on 10 November 2006]

I recently read Gisle's "When I'm 64" article in Acucorp News(http://www.acucorp.com/company/newsletter/newsletter_featured/featured_6.php). The articles states:
The 64-bit architecture implies that Windows supports 32 GB of memory, with a theoretical limit of 16 TB. Yes, that’s right—16 terra bytes.

Is this correct? 16 TB is 2^44, whereas 2^64 is 16 EB(Exabytes). So, shouldn't it "in theory" be 16 EB? Am I incorrect?

I'm just being curious as 16 TB and EB are numbers so large that we'll never use or create applications that require, nor have PC's with that much virtual memory in our lifetime. 🙂 Or will we? Hmm.....
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RE: [archive] When I'm 64 in Acucorp News

Dan, you really ought to get a life 🙂

Seriously, I have to admit that I have these numbers from Microsoft (yepp, I shamelessly copied the numbers) and as such, I have not verified them. It might very well be that you are right, or there might be other reasons there is a limit in TB not EB. But, as you point out, we will probably never get into such sizes anyway. 😉
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RE: [archive] When I'm 64 in Acucorp News

Dan, you really ought to get a life 🙂


Well, someone has to keep you on your toes. 😄

Wikipedia speaks a bit about Win 64 and memory limits: http://en.wikipedia.org/wiki/Windows_XP_Professional_x64_Edition
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RE: [archive] When I'm 64 in Acucorp News

In theory, 64-bit CPUs can address 2^64.

But current 64-bit CPU's like the AMD64 are only using 48 bits for address translation, and current 64-bit Windows versions are only using 44 bits (16 TB) for addressing.
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RE: [archive] When I'm 64 in Acucorp News

Thanks for the support! 🙂

It is a classic phenomena really. Had similar cases with the 8086, 80286 and 80386 processors from Intel.

Anyways, I figure we can say we are all correct, just depending on from what angle one look at it 🙂

Gisle
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RE: [archive] When I'm 64 in Acucorp News

In theory, 64-bit CPUs can address 2^64.

But current 64-bit CPU's like the AMD64 are only using 48 bits for address translation, and current 64-bit Windows versions are only using 44 bits (16 TB) for addressing.


Thanks Joe, good to know. 🙂
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