[haiku-development] Re: A 64-bit OS question...
- From: Ingo Weinhold <ingo_weinhold@xxxxxx>
- To: haiku-development@xxxxxxxxxxxxx
- Date: Sun, 17 Oct 2010 16:32:57 +0200
On 2010-10-16 at 19:15:53 [+0200], Urias McCullough <umccullough@xxxxxxxxx>
wrote:
> Note that x86-64 isn't really a true 64bit architecture (like IA-64),
> insomuch as it's basically just an extension on the x86-32
> architecture to increase memory address sizes, some additional
> instructions, and extra registers (at least, that's my understanding).
> Processors supporting x86-64 still utilize all the older 32bit
> instructions for compatibility.
In 64 bit mode (aka long mode) registers are 64 bit wide and the instructions
operate on the full width of registers. So in this respect x86-64 is as 64
bit as it gets -- the 32 and 16 bit modes can be considered compatibility
modes.
Where the architecture actually falls short of being truly 64 bit is the
range of addressable virtual and physical memory, which is limited to 48 bit
respectively 48 - 52 bit (model specific). So mmap()ing 256 TiB files is not
going to be possible for the time being. :-)
CU, Ingo
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