Groups > comp.lang.java.programmer > #19760

Re: Program in 32-bit, run on 64-bit OK?

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From	Stuart <DerTopper@web.de>
Newsgroups	comp.lang.java.programmer
Subject	Re: Program in 32-bit, run on 64-bit OK?
Date	Fri, 16 Nov 2012 00:08:58 +0100
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On 11/15/12 sl@exabyte wrote:
[snip]
> And I suppose only hardware with 64-bit address bus can run 64-bit OS.

Wrong. Typical 64 bit processors have either a 36 bit or a 40 bit 
physical address bus (40 bits are 1 TB, an almost incredible amount of 
RAM, wikipedia mentions that some AMD chips even offer a 48 bit memory 
bus). Note that bus width and register width do not have to have a 
one-to-one relationship. The early 286 processor had a register width of 
16 bits but an address bus with 24 bits (4MB), so they had to invent 
this segmentation model in order to compute a 20bit address from two 16 
bit registers. Twenty years later, the segmenation unit is still present 
at the Intel architecture while the numbers have been reversed: now the 
36 or 40 bit physical address is computed from a 16 bit value and a 64 
bit value. Sounds like overkill, and yes, it is. That's just for 
backwards compatibility for applications from 1985.

Regards,
Stuart

Thread

Program in 32-bit, run on 64-bit OK? "sl@exabyte" <sb5309@hotmail.com> - 2012-11-14 21:58 +0800
  Re: Program in 32-bit, run on 64-bit OK? "sl@exabyte" <sb5309@hotmail.com> - 2012-11-14 22:01 +0800
  Re: Program in 32-bit, run on 64-bit OK? Arne Vajhøj <arne@vajhoej.dk> - 2012-11-14 09:12 -0500
    Re: Program in 32-bit, run on 64-bit OK? Cholo Lennon <chololennon@hotmail.com> - 2012-11-14 14:11 -0300
      Re: Program in 32-bit, run on 64-bit OK? Arne Vajhøj <arne@vajhoej.dk> - 2012-11-14 12:14 -0500
        Re: Program in 32-bit, run on 64-bit OK? Joerg Meier <joergmmeier@arcor.de> - 2012-11-14 18:36 +0100
          Re: Program in 32-bit, run on 64-bit OK? "sl@exabyte" <sb5309@hotmail.com> - 2012-11-15 10:48 +0800
            Re: Program in 32-bit, run on 64-bit OK? Stuart <DerTopper@web.de> - 2012-11-16 00:08 +0100
              Re: Program in 32-bit, run on 64-bit OK? "SL@maxis" <ecp_gen@my-rialto.com> - 2012-11-16 09:23 +0800
                Re: Program in 32-bit, run on 64-bit OK? BGB <cr88192@hotmail.com> - 2012-11-15 22:52 -0600
                Re: Program in 32-bit, run on 64-bit OK? Fritz Wuehler <fritz@spamexpire-201211.rodent.frell.theremailer.net> - 2012-11-16 16:44 +0100
                Re: Program in 32-bit, run on 64-bit OK? Joerg Meier <joergmmeier@arcor.de> - 2012-11-17 13:18 +0100
                Re: Program in 32-bit, run on 64-bit OK? BGB <cr88192@hotmail.com> - 2012-11-17 12:42 -0600
              Re: Program in 32-bit, run on 64-bit OK? BGB <cr88192@hotmail.com> - 2012-11-15 22:46 -0600
                Re: Program in 32-bit, run on 64-bit OK? Stuart <DerTopper@web.de> - 2012-11-16 12:08 +0100
                Re: Program in 32-bit, run on 64-bit OK? BGB <cr88192@hotmail.com> - 2012-11-16 18:08 -0600
                Re: Program in 32-bit, run on 64-bit OK? Stuart <DerTopper@web.de> - 2012-11-17 23:59 +0100
              Re: Program in 32-bit, run on 64-bit OK? Anonymous <nobody@remailer.paranoici.org> - 2012-11-16 12:42 +0000
            Re: Program in 32-bit, run on 64-bit OK? Roedy Green <see_website@mindprod.com.invalid> - 2012-11-16 05:17 -0800
    Re: Program in 32-bit, run on 64-bit OK? Jan Burse <janburse@fastmail.fm> - 2012-11-14 20:08 +0100

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