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/3GB

 
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DanRRight



Joined: 10 Mar 2008
Posts: 1645
Location: South Pole, Antarctica

PostPosted: Fri Mar 21, 2014 10:17 pm    Post subject: /3GB Reply with quote

Documentation says "The address space is reduced to 2Gb by most operating systems. However, some operating systems, including Windows XP Professional, provide a /3GB switch in boot.ini that extends the user's address space to 3GB"

I see this switch with 64bit Windows 7/8 actually gets closer to 4GB. Am i right, John ?
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JohnCampbell



Joined: 16 Feb 2006
Posts: 1835
Location: Sydney

PostPosted: Mon Mar 24, 2014 1:20 am    Post subject: Reply with quote

Dan,

With Windows 7_64, the extended addressable memory is default and you do not need to boot with the /3gb switch, which was the case for XP_32. I have not done any testing of Windows 8 (for any work) as yet! I hope cmd.exe is like Windows 7 and that control panel > system and task manager are still available.

With Windows 7, I can get small programs to access up to about 3.6 Gb. It would be good to have a version of LOC that was Integer*8, that makes it easier to check the addresses, although that can be overcome. (The intrinsic SIZEOF would also be a valuable addition for this testing.)

The problem I have not yet solved is I can not get more than 2Gb in my large clearwin+ program. I don't know the cause, as Paul changed /debug to still allow extra memory to be available.

Note: you can only get memory above 2Gb for ALLOCATE arrays, which is the case for any 64 bit coding. This helps with testing of 64 bit code, using FTN95's superior error checking at compile time, although I have not tested SDBG for above 2Gb.

John
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