Re: Overflows (lisp fixnum-bignum conversion)

[jvl@ocsystems.com (Joel VanLaven)]

Larry Kilgallen (kilgallen@eisner.decus.org) wrote:
: In article <dewar.860424609@merv>, dewar@merv.cs.nyu.edu (Robert Dewar) writes:
: > Bob Duff said
: > 
: > <<(By the way, in going from a 32-bit address to a 64-bit address, don't
: > think in terms of doubling the size of the address.  In fact, you're
: > multiplying the the size of the address space by about 4 billion, which
: > is an awful lot.  Much bigger than the switch from 16 to 32.  It's hard
: > for me to even imagine how big 2**64 bytes is.)>>
: > 
: > Yes, but this is address space, not actual data in a program, if you start
: > mappiong entire file systems into virtual memory, you can be surprised how
: > fast the 64 bits gets eaten up.

: I don't see it going that fast.  Disks I use hold 1 GB, while others
: can hold 4 or 9 GB.  64 bits allows me to address the contents of about
: 2,000,000,000 of the 9 GB drives.  How many disk drives have ever been
: built ?

I aggree.  Given progress similar to history, 64 bits ought to be enough
for many decades.  Assuming that capacity doubles every two years and
that only highly specialized systems today would need more than 1 terrabyte
of disk space, the first time 64 bit addresses will not cover a very large
filesystem will be in about 48 years.  The average 4gig home system 
(extrapolated) won't hit that barrier for another 16 years after that.
Before either UNIX 32-bit times will wrap around.  In between we will
probably think that 32 bit addressing wasn't enough but 64 bits is more
than enough.

-- Joel.
-- 
-- Joel VanLaven