Guest JM Posted August 5, 2008 Posted August 5, 2008 I was told by someone that you must use 8GB of RAM to fully use 64bit memory addressing. I have never heard of this and I can't find any information on it.
Guest dennis Posted August 5, 2008 Posted August 5, 2008 Re: 8GB of RAM to fully use 64bit memory addressing with 64bit Server JM wrote: > I was told by someone that you must use 8GB of RAM to fully use 64bit memory > addressing. I have never heard of this and I can't find any information on it. > http://forums.anandtech.com/messageview.aspx?catid=83&threadid=2214112&enterthread=y
Guest JM Posted August 5, 2008 Posted August 5, 2008 Re: 8GB of RAM to fully use 64bit memory addressing with 64bit Ser Re: 8GB of RAM to fully use 64bit memory addressing with 64bit Ser I read all of those responses but I probably should have given more information. I currently test a 32bit application that is being ported to 64bit. I needed to know whether or not I would be able to properly test the changes using only 4GB of RAM on a 64bit OS. I was told that the memory space on a 4GB machine is only using the 32bit memory space and that I would need to have over 4GB of RAM to exercise the 64bit memory space.
Guest Justin Rich Posted August 5, 2008 Posted August 5, 2008 Re: 8GB of RAM to fully use 64bit memory addressing with 64bit Ser Re: 8GB of RAM to fully use 64bit memory addressing with 64bit Ser only if your app needs to use large amounts of memory. if you think your app will eat more than 2gb of user space, then its worth testing. i would say over all your pretty safe using 4gb of ram to test 64 bit because of the way the VMM works. I think the only real concern you would have for over 4gb is if you were testing a 32bit app on a 64bit system. in that case there is a boot option that will allow you to have apps start loading above the 4gb mark to see if they are handled correctly.. "JM" <JM@discussions.microsoft.com> wrote in message news:BA16CAD8-AC5E-403F-BEA5-8BCE97C061CF@microsoft.com... >I read all of those responses but I probably should have given more > information. I currently test a 32bit application that is being ported to > 64bit. I needed to know whether or not I would be able to properly test > the > changes using only 4GB of RAM on a 64bit OS. I was told that the memory > space > on a 4GB machine is only using the 32bit memory space and that I would > need > to have over 4GB of RAM to exercise the 64bit memory space.
Guest Bruce Sanderson Posted August 6, 2008 Posted August 6, 2008 Re: 8GB of RAM to fully use 64bit memory addressing with 64bit Ser Re: 8GB of RAM to fully use 64bit memory addressing with 64bit Ser You may find the article at http://members.shaw.ca/bsanders/WindowsGeneralWeb/RAMVirtualMemoryPageFileEtc.htm useful. See in particular sections 2.2 and 2.4 and 3. If your appplication is built to use the 64 bit instruction set, the 64 bit version of Windows will create a "64 bit" adress space for it - 8 TB of private address space, regardless of how much RAM is in the computer. If your application then proceeds to use more of the address space than there is available RAM, some of it will be paged out. This will affect performance, but not the function of the application. Even on 64 bit Windows installation, 32 bit applications will only get a 32 bit address space - 2 GB or private space (unless the /3GB boot switch is used or the application uses the AWE API - sections 2.5 and 2.6). -- Bruce Sanderson http://members.shaw.ca/bsanders It is perfectly useless to know the right answer to the wrong question. "JM" <JM@discussions.microsoft.com> wrote in message news:BA16CAD8-AC5E-403F-BEA5-8BCE97C061CF@microsoft.com... >I read all of those responses but I probably should have given more > information. I currently test a 32bit application that is being ported to > 64bit. I needed to know whether or not I would be able to properly test > the > changes using only 4GB of RAM on a 64bit OS. I was told that the memory > space > on a 4GB machine is only using the 32bit memory space and that I would > need > to have over 4GB of RAM to exercise the 64bit memory space.
Guest Gander Posted August 6, 2008 Posted August 6, 2008 Re: 8GB of RAM to fully use 64bit memory addressing with 64bit Ser Re: 8GB of RAM to fully use 64bit memory addressing with 64bit Ser Bruce Sanderson skrev: > Even on 64 bit Windows installation, 32 bit applications will only get a > 32 bit address space - 2 GB or private space (unless the /3GB boot > switch is used or the application uses the AWE API - sections 2.5 and 2.6). > On 64bit Windows the application will be allowed to grow to 4GB, if the largeaddressawarebit is set. I don't think the /3gb switch exits on 64bit Win
Guest Bruce Sanderson Posted August 8, 2008 Posted August 8, 2008 Re: 8GB of RAM to fully use 64bit memory addressing with 64bit Ser Re: 8GB of RAM to fully use 64bit memory addressing with 64bit Ser Gander: thank you for pointing that out! I thought I remembered reading something about that and found it in http://support.microsoft.com/?kbid=294418 and also http://msdn.microsoft.com/en-us/library/aa366778.aspx. I've made some updates to the document at http://members.shaw.ca/bsanders/WindowsGeneralWeb/RAMVirtualMemoryPageFileEtc.htm: 1. revised section 2.3 Pagefile to reflect that most computers these days have 1 GB RAM or more 2. added 2.5.3. about 32 bit applications with the IMAGE_FILE_LARGE_ADDRESS_AWARE bit on will get 4 GB of private address space on 64 bit Windows as you pointed out. 3. verified the maximum RAM for 32 bit and 64 bit Windows version from the referenced Microsoft documents 4. other minor updates. I noticed that the document at http://msdn.microsoft.com/en-us/library/aa366778.aspx says" "User-mode virtual address space for 64-bit processes" is 2 GB unless the IMAGE_FILE_LARGE_ADDRESS_AWARE bit is on. However, the "Benefits of Microsoft Windows x64 Editions" downloadable from http://www.microsoft.com/windowsserver2003/techinfo/overview/x64benefits.mspx appears to contradict this with this statement: "Windows x64 Editions can address a full 16 TB of virtual memory by using a flat addressing model. This 16 TB is divided up into equal buckets of 8 TB of virtual address space for applications and 8 TB for the operating system." If anyone can definitively clarify this (someone from the Microsoft Windows kernel team perhaps?) I'd appreciate it. If anyone notices any other errors or has other comments about it, please post here. -- Bruce Sanderson http://members.shaw.ca/bsanders It is perfectly useless to know the right answer to the wrong question. "Gander" <gander@.> wrote in message news:%23VW4r$59IHA.1196@TK2MSFTNGP05.phx.gbl... > Bruce Sanderson skrev: > >> Even on 64 bit Windows installation, 32 bit applications will only get a >> 32 bit address space - 2 GB or private space (unless the /3GB boot switch >> is used or the application uses the AWE API - sections 2.5 and 2.6). >> > > On 64bit Windows the application will be allowed to grow to 4GB, if the > largeaddressawarebit is set. I don't think the /3gb switch exits on 64bit > Win
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