On Fri, October 31, 2014 9:56 pm, John R Pierce wrote:
> On 10/31/2014 8:38 PM, Always Learning wrote:
>> Hmm, I wonder when 128-bit processors will appear
>
> a 32 bit address got us up to 4,000,000,000 (4 billion) bytes of
> directly addressible memory.
>
> a 64 bit address gets you into a 18,440,000,000,000,000,000 byte address
> space. I think thats 18 zetabytes. It will be a long time before
> we'll need a larger address space.
>
Of course, the address space is the main consideration. There is one more
property: "dynamic range" which is the ratio of maximum number you can use
in operation to error (which is the value of least significant bit (LSB)
multiplied by some small number the last depends on what kind of operation
its is, let's say, you may loose LSB a few times during the operation).
But this is really minor thing compared to the size of space one can
address, as these can be achieved by programming several regular
operations for each operation with "larger" numbers (or "higher precision"
rather).
So, I would just echo what you said: we hardly will see the need in 128
bit CPUs soon. (BTW, I'm glad to hear the choice which is power of 2. As,
in general, the length of CPU word can be anything: 17, 89, ... I'm not
mentioning 1 which is used in calculators, as 1 _is_ power of 2 ;-)
Valeri
++++++++++++++++++++++++++++++++++++++++
Valeri Galtsev
Sr System Administrator
Department of Astronomy and Astrophysics
Kavli Institute for Cosmological Physics
University of Chicago
Phone: 773-702-4247
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