Program Addressing Limit

Jeff Whittle · 02-01-2008, 06:10 PM

On a 32 bit PC the maximum memory for the program and data of an application is usually 2GB (31 address bits).

I have been told that some operating systems allow a program to access 4GB (32 address bits).

Is this true and, if so, which operating systems do it?

I am aware that 64 bit processors get round this problem but the cost of software that I need for that is very high.

Thanks
Jeff Whittle

belfasteddie · 02-07-2008, 02:11 PM

I was reading an article recently , one of the points made was the 32 bit addressing was somewhat artificial. One of the Microsoft products(server?) can address 36 bit . An aside to this, Microsoft was of the opinion it was too much trouble to go to this type of addressing for general use.
Found this:http://www.everything2.com/index.pl?...&lastnode_id=0

lensman3 · 04-22-2008, 07:29 PM

Interesting point by M$ and is probably true. 64-bit programs are about 20% larger than the equivalent 32-bit (I'm comparing Linux installs). I'm not sure that the Intel or AMD hardware is doing 64-bit instruction fetches from memory. If they are doing 32-bit fetches and putting them together to make 64-bit then the software probably runs at 1/2 the speed. Is the data bus really 64-bits? Anybody know?

I work in GIS and use ArcGIS and Autocad everyday. I know that the 32-bit version of these programs have about hit the performance wall when rendering large drawings. The only place, I think, that performance can improve is in the 64-bit arena. A large drawing can use up more the 4 Gbytes of in data space.

02-01-2008, 06:10 PM	#1 (permalink)
Jeff Whittle Registered User Join Date: Jan 2008 Posts: 5 OS: win98	Program Addressing Limit On a 32 bit PC the maximum memory for the program and data of an application is usually 2GB (31 address bits). I have been told that some operating systems allow a program to access 4GB (32 address bits). Is this true and, if so, which operating systems do it? I am aware that 64 bit processors get round this problem but the cost of software that I need for that is very high. Thanks Jeff Whittle

02-07-2008, 02:11 PM	#2 (permalink)
belfasteddie Registered User Join Date: Aug 2007 Posts: 339 OS: Suse 10.2 64 bit	Re: Program Addressing Limit I was reading an article recently , one of the points made was the 32 bit addressing was somewhat artificial. One of the Microsoft products(server?) can address 36 bit . An aside to this, Microsoft was of the opinion it was too much trouble to go to this type of addressing for general use. Found this:http://www.everything2.com/index.pl?...&lastnode_id=0 Last edited by belfasteddie : 02-07-2008 at 02:19 PM.

04-22-2008, 07:29 PM	#3 (permalink)
lensman3 Registered User Join Date: Oct 2007 Location: Littleton, Colorado USA Posts: 343 OS: xp 64 sp2 Fedora Core 8 (vmware xp core 8 x32) Minix	Re: Program Addressing Limit Interesting point by M$ and is probably true. 64-bit programs are about 20% larger than the equivalent 32-bit (I'm comparing Linux installs). I'm not sure that the Intel or AMD hardware is doing 64-bit instruction fetches from memory. If they are doing 32-bit fetches and putting them together to make 64-bit then the software probably runs at 1/2 the speed. Is the data bus really 64-bits? Anybody know? I work in GIS and use ArcGIS and Autocad everyday. I know that the 32-bit version of these programs have about hit the performance wall when rendering large drawings. The only place, I think, that performance can improve is in the 64-bit arena. A large drawing can use up more the 4 Gbytes of in data space.