[Discuss] Unix date beyond 2057

[John Blomfield]

Deryk Barker wrote:
> Thus spake John Blomfield (jabfield at shaw.ca):
> ...
>   
>>> That is an illustration of Eric Raymond's point that there is no 
>>> conceivable
>>> need for machines with word lengths larger than 64 bits so he predicts 
>>> the
>>> current transition from 32-bit to 64-bit that is going on is probably the
>>> last such transition for the human race.  Normally, I pooh-pooh any such
>>> conclusion about limits for computers because so many have been so wrong
>>> about that before, but nevertheless, a 128-bit machine would have integer
>>> ranges that are 2^{64} times larger than a current 64-bit machine, and it
>>> really is hard to conceive of any practical software application that 
>>> would
>>> overflow such a huge integer range.
>>>
>>>       
>> Such a machine is probably of interest to groups involved with the 
>> mathematical modeling (numerical analysis) of complex physical systems 
>> e.g. weather forecasting, climate models, aerodynamic fluid flow etc. 
>> that are essentially solving initial value multi-dimensional 
>> differential equations, stepping forward into time.  These models suffer 
>> from rounding errors and the difficulty of predicting the propagation of 
>> butterfly type events.  In these cases the more precision i.e. the more 
>> bits per word the better.  Having said that this is normally the realm 
>> of the big number crunching machines that are probably already 128 bit 
>> (I'm a bit out of touch these days) and not the PC world.
>>     
>
> A quick persual of the Top500 list shows that the ost powerful achine
> in the world (as of last November), the IBM BlueGene/L, is built from
> 212992 PowerPC 440 CPUs - a 32-bit chip. The system has 73728 GB of
> RAM. I want one!
>
>   
Back in the 1960's I used a Ferranti computer with a 40 bit CPU and then 
an ICL with 48 bit words.  I was most disappointed when this was 
replaced by an IBM 7090/94 with 32 bit words but this was soon replaced 
by a CDC 6600 and 7600 with 60 bit words. According to Wikipedia,

"IBM System 370, could be considered the first rudimentary 128-bit 
computer as it used 128-bit floating point registers."

It all gets a bit confusing because sometimes references are to memory 
word length and sometimes to integer registers in the CPU and sometimes 
to floating point arithmetic units.  In 32 bit CPU machines greater 
precision is achieved with software at the cost of speed.

John Blomfield