When a 64 bit OS isn't enough for the memory installed

[Modelworks]

Was doing something last night related to factorials and 64bit limitations and it got me thinking to how much memory a 64 bit OS can address.

We made the jump from a 32bit OS to a 64 bit OS to move up in memory useable by the OS. So how much memory has to be installed before we have to make the jump to a 128 bit OS ?

17,179,869,185 GB.

I can't imagine what someone would do with that much memory.
I bet they look back on us with our 2GB memory the way we do with the 64K statements Gates made years ago

 

[imported_wired247]

couldn't there be other compelling reasons to go with a 128 bit OS? other than maximum memory?

 

[Modelworks]

Originally posted by: wired247
couldn't there be other compelling reasons to go with a 128 bit OS? other than maximum memory?

Mainly the only reason currently is if you start using really really large numbers.

 

[imported_wired247]

so, are "really large numbers" used in grapihcs calculations?

I noticed that many GPUs are 128 bit, 256 bit... etc.

 

[Sheninat0r]

Wired, are you sure that's not memory bus size? Having a 128- or 256-bit processor is pretty much insane... and how would it get instructions in that word size from the 32- or 64- bit OS? Or am I just crazy?

 

[aka1nas]

Originally posted by: Sheninat0r
Wired, are you sure that's not memory bus size? Having a 128- or 256-bit processor is pretty much insane... and how would it get instructions in that word size from the 32- or 64- bit OS? Or am I just crazy?

Yes, that is the memory bus width.

 

[Modelworks]

yep memory bus .
from the wiki:

In computer architecture, 128-bit integers, memory addresses, or other data units are those that are at most 128 bits wide. Also, 128-bit CPU and ALU architectures are those that are based on registers, address buses, or data buses of that size.

There are currently no mainstream general-purpose processors built to operate on 128-bit integers or addresses, though a number of processors do operate on 128-bit data. System/370, made by IBM, could be considered the first rudimentary 128-bit computer as it used 128-bit floating point registers. Most modern CPUs such as the Pentium and PowerPC have 128-bit vector registers used to store several smaller numbers, such as four 32-bit floating-point numbers. A single instruction can operate on all these values in parallel (SIMD). They are 128-bit processors in the sense that they have 128-bit registers and in some cases a 128-bit ALU, but they do not operate on individual numbers that are 128 binary digits in length.

When I said very large numbers I mean numbers that are like 1,000,000,000 digits in length.

 

[imported_wired247]

My mistake, thanks for the clarification.

 

[her209]

When there is a need for virtual memory space larger than 16 EB.