A Fast, Growable Array with Stable Pointers in C

Re:A Fast, Growable Array with Stable Pointers in C by hinkley on Wednesday August 06, 2025 @06:18PM (#44818525)

And how long has 48 bit addressing been de rigeur? Not so long ago we had processors that could address 40 bits of address space. Or was that 38?

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Re:A Fast, Growable Array with Stable Pointers in C by winocm on Wednesday August 06, 2025 @06:28PM (#44818601)

At least since maybe the DEC Alpha 21264. It could address 48-bits of VA space, but that comes with caveats due to PALcode specific intricacies.

I think VMS (or was it Tru64?) uses this mode, but many other OSes just use 43-bit or 40-bit addressing. Realistically though, I don’t think many users would be using workloads that addressed more than 38-bits worth of contiguous VA space in 1998-1999.

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Re:A Fast, Growable Array with Stable Pointers in C by loeg on Wednesday August 06, 2025 @07:52PM (#44819209)

amd64 has had 48-bit addressing / 4-level paging from the beginning.

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Re:A Fast, Growable Array with Stable Pointers in C by hinkley on Thursday August 07, 2025 @07:21PM (#44831612)

I must be thinking of intel’s failed 64 bit attempts prior to amd64 winning.

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Re:A Fast, Growable Array with Stable Pointers in C by wittystick on Friday August 08, 2025 @08:37PM (#44843088)

Physical addresses may be limited to 40 bits, but 48-bit virtual addresses have been the norm since 4-level paging.

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Re:A Fast, Growable Array with Stable Pointers in C by bonzini on Wednesday August 13, 2025 @07:09PM (#44894963)

You're probably thinking of PAE (36 bit physical address space on 32 bit virtual address space). But Intel for quite some time had a 36 bit physical address space limit on 64-bit consumer processors, even if the virtual address space was 48 bits. I think it only changed 5 years ago or less.

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