Year 2038 preparations in 3.17

Posted Aug 9, 2014 11:21 UTC (Sat) by Thue (guest, #14277)
In reply to: Year 2038 preparations in 3.17 by Villemoes
Parent article: Year 2038 preparations in 3.17

> Maybe 128 bit architectures appear in the next 100 years, then there's still plenty of time to do the next transition.

It seems unlikely to me that 128 bit general purpose architectures will be built. There are simply so few places that need 128 bit integers that it is more efficient to emulate them when needed, like GCC's current __int128_t. And for addressing, 64 bit should be enough.

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Year 2038 preparations in 3.17

Posted Aug 9, 2014 16:40 UTC (Sat) by Cyberax (✭ supporter ✭, #52523) [Link] (4 responses)

Well, 2^64 is close to 1 mole of bits. If we ever have near-atomic-density storage then it's not inconceivable that a computer might need more than 2^64 of addressable space.

2^128 seems to be safe, on the other hand. It's just not feasible to fill that much RAM with a classic computer.

Year 2038 preparations in 3.17

Posted Aug 11, 2014 13:38 UTC (Mon) by robbe (guest, #16131) [Link] (3 responses)

For some values of "close" ... Avogardo's number is in the 2^76 range.

If Moore's law holds for the next 50 years, we will see computers exhausting 64bit address space by then.

So we may run out of bits before we run out of fossile fuel to power this monsters.

Year 2038 preparations in 3.17

Posted Aug 11, 2014 14:46 UTC (Mon) by Cyberax (✭ supporter ✭, #52523) [Link] (2 responses)

Yes, it's not outrageously out of range. And you might still want to have more address space than actual addressable RAM.

As far as I remember, filling 2^64 bits requires _at_ _minimum_ enough energy to boil 10 liters of water. So these computers are definitely not going to be environment-friendly.

Year 2038 preparations in 3.17

Posted Aug 11, 2014 18:13 UTC (Mon) by dlang (guest, #313) [Link]

it all depends on how frequently you are refilling that memory, and how much other useful work gets done.

There's no amount of power usage that's automatically "environmentally unfriendly"

Year 2038 preparations in 3.17

Posted Aug 17, 2014 18:03 UTC (Sun) by Jandar (subscriber, #85683) [Link]

> As far as I remember, filling 2^64 bits requires _at_ _minimum_ enough energy to boil 10 liters of water.

I recall reading in a paper that there is no lower energy limit to *filling* memory, but there is a lower energy limit to *clear* memory since clearing restores order thus lowers entropy. Maybe with enough bits we can skip clearing and save energy with write-once memory :-).