OS for 4GB RAM
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From: gnu / linux on 2 Apr 2010 20:16 On Apr 2, 7:12 pm, "Jeff Strickland" <crwlrj...(a)yahoo.com> wrote: > "sandy58" <alecki...(a)googlemail.com> wrote in message > > news:84997128-2b8c-45dd-a19f-de07cf91fce7(a)10g2000yqq.googlegroups.com... > On Apr 2, 7:55 pm, "James D. Andrews" <jamesdandr...(a)att.net> wrote: > > > Do I need to use a 64-bit OS with 4GB RAM, or will 32-bit work? I was > > reading today that the 32-bit will only support 3GB. Don't know how true > > that is. > > > I suppose it would be nice to know before I go and buy an OS. > > > --- news://freenews.netfront.net/ - complaints: n...(a)netfront.net --- > > 32-bit won't use 4gb ram. 3gb is about it. > 64-bit will use as much as you can get in. > > <JS> > I'm using all 4G of RAM in my machine. I have 32-bit XP Pro. > > </JS> 32 bit will use most all of the 4 GB
From: Jeff Strickland on 2 Apr 2010 20:31 "gnu / linux" <rob.fruth(a)gmail.com> wrote in message news:b35c497d-ec86-4db3-9e9e-8b4aee2d09ac(a)e7g2000yqf.googlegroups.com... On Apr 2, 7:12 pm, "Jeff Strickland" <crwlrj...(a)yahoo.com> wrote: > "sandy58" <alecki...(a)googlemail.com> wrote in message > > news:84997128-2b8c-45dd-a19f-de07cf91fce7(a)10g2000yqq.googlegroups.com... > On Apr 2, 7:55 pm, "James D. Andrews" <jamesdandr...(a)att.net> wrote: > > > Do I need to use a 64-bit OS with 4GB RAM, or will 32-bit work? I was > > reading today that the 32-bit will only support 3GB. Don't know how true > > that is. > > > I suppose it would be nice to know before I go and buy an OS. > > > --- news://freenews.netfront.net/ - complaints: n...(a)netfront.net --- > > 32-bit won't use 4gb ram. 3gb is about it. > 64-bit will use as much as you can get in. > > <JS> > I'm using all 4G of RAM in my machine. I have 32-bit XP Pro. > > </JS> 32 bit will use most all of the 4 GB <JS> That's my point. The person I was replying to said that only 3G is supported by 32-bit systems. </JS>
From: Robert Baer on 3 Apr 2010 13:01 James D. Andrews wrote: > Do I need to use a 64-bit OS with 4GB RAM, or will 32-bit work? I was > reading today that the 32-bit will only support 3GB. Don't know how true > that is. > > I suppose it would be nice to know before I go and buy an OS. > > > > > --- news://freenews.netfront.net/ - complaints: news(a)netfront.net --- Win2K seems to be the oldest M$ OS that supports 4Gbytes of RAM.
From: Paul on 3 Apr 2010 03:30 Jeff Strickland wrote: > "gnu / linux" <rob.fruth(a)gmail.com> wrote in message > news:b35c497d-ec86-4db3-9e9e-8b4aee2d09ac(a)e7g2000yqf.googlegroups.com... > On Apr 2, 7:12 pm, "Jeff Strickland" <crwlrj...(a)yahoo.com> wrote: >> "sandy58" <alecki...(a)googlemail.com> wrote in message >> >> news:84997128-2b8c-45dd-a19f-de07cf91fce7(a)10g2000yqq.googlegroups.com... >> On Apr 2, 7:55 pm, "James D. Andrews" <jamesdandr...(a)att.net> wrote: >> >>> Do I need to use a 64-bit OS with 4GB RAM, or will 32-bit work? I was >>> reading today that the 32-bit will only support 3GB. Don't know how true >>> that is. >>> I suppose it would be nice to know before I go and buy an OS. >> 32-bit won't use 4gb ram. 3gb is about it. >> 64-bit will use as much as you can get in. >> >> <JS> >> I'm using all 4G of RAM in my machine. I have 32-bit XP Pro. >> >> </JS> > > 32 bit will use most all of the 4 GB > > > > <JS> > That's my point. The person I was replying to said that only 3G is supported > by 32-bit systems. > > </JS> > This depends a lot, on the details. As JS mentioned via a link at the end of his posting, there is a hardware feature called PAE, that maps 32 bit addresses to a 36 bit physical address space. Intel processors and chipsets have had PAE capability for some time. And PAE allows a 32 bit OS to address up to 64GB of installed memory. (Modern PAE can support more than 36 bits, so more is possible. For example, on modern AMD processors, it goes to 40 bits.) It is possible that some early version of WinXP, still properly supported PAE. But in later Service Packs, a bit was borrowed for something like NX (no execute) bit. That was a security feature. At the same time, they decided it would be fun to prevent PAE from accessing more than 4GB. I'm a little fuzzy on the details. There is a discussion about this topic, here. This person hacked an MS OS, to prove that more than 4GB can be addressed by a 32 bit OS. It works. http://www.geoffchappell.com/viewer.htm?doc=notes/windows/license/memory.htm So, if the OS has PAE neutered, then indeed there might be only 4GB of address space available via the 32 bit OS. From that, the hardware devices (like the memory on the video card), has to be addressable. And after all the addresses for the various hardware busses have been assigned by the BIOS, the remainder is used to provide access to the memory DIMMs. If you install 4GB worth of DIMMs, and happened to use an old PCI video card with small resident memory, you might see reported that you have 3.5GB free. (Bus address space is assigned in 256MB chunks, and with PCI/AGP or PCI/PCI Express, you might lose two chunks to start with. Once the actual hardware rolls over that assignment, another chunk would be mapped in. So the assignment process has a relatively coarse granularity.) If you install a couple Nvidia video cards in SLI, with 512MB of memory on each card, and happen to have 4GB memory installed, and have the neutered OS running, then the free memory reported once the OS is running, could be as low as 2.75GB (someone reported that, on an S939 board). Which negates the purpose of installing that much memory to begin with. If you had a monster video setup, you might be better off installing 2x1GB + 2x512MB sticks, for a total of 3GB dual channel mode. And then, you'd still see the 2.75GB free reported, and would only be losing 0.25GB. Or, you could use a 64 bit OS, and have it all. In terms of the memory configuration, a lot of people would choose to use 2x2GB, as it may support a higher max operating frequency for the DIMMs. And then take the loss, on whatever amount of memory is inaccessible by the OS. Using a four stick configuration, might not clock quite as high. The details are a bit fuzzy, as to whether there is a good reason for PAE to not work on WinXP x32. But it would certainly push sales of alternate OS solutions. (And no, WinXP x64 is not a good choice. It was a little rough around the edges.) If you use PAE, one of the limitations would be, that a single program could not use all the memory on the computer. If you had 8GB of RAM installed, used a 32 bit OS, you would need two programs, accessing 4GB each, to use all the memory. There might even be further restrictions, as to the maximum memory that any program or process could use (user/kernel split?). So even if PAE was working, it is a less ideal situation than using a 64 bit OS to solve the addressing limitations. But PAE does have the advantage, that it has been available in hardware for a long time. It is only now, that ordinary desktops can easily reach those memory limits. http://en.wikipedia.org/wiki/Physical_Address_Extension "Windows XP Service Pack 2 and later, by default, on processors with the no-execute (NX) or execute-disable (XD) feature, runs in PAE mode in order to allow NX. The no execute (NX, or XD for execution disable) bit resides in bit 63 of the page table entry and, without PAE, page table entries on 32-bit systems have only 32 bits; therefore PAE mode is required if the NX feature is to be exploited. However, "client" versions of 32-bit Windows (Windows XP, Windows Vista, Windows 7) limit physical address space to the first 4 GB for driver compatibility and *licensing* reasons, even though these versions do run in PAE mode if NX support is enabled." So that tells you, the limitation is artificial. There are some other things to consider, before making the OS choice. For example, how much memory does the software you own, want to use ? I have a copy of Photoshop, that won't go above 1.8GB on a 4GB system. For the people that own large quantities of memory, I'd be interested in what exactly they've been able to get out of it. I wasted a couple hours on the topic and gave up (my machine is back to 2GB now). I don't seem to have anything which is IMAGE_FILE_LARGE_ADDRESS_AWARE. I could certainly run a couple different programs, to use the RAM, such as some VPC2007 sessions. And that is the most likely thing here, that would benefit from 4GB. For a lot of other stuff, 2GB is enough for me. http://en.wikipedia.org/wiki/RAM_Limit A 64 bit OS, makes some of the issues more transparent. But does not guarantee that a single program can use all available memory. For example, if you have a 64 bit executable, running on a 64 bit OS, that removes the limits. But other combinations could still have limits, like running existing 32 bit programs on a 64 bit OS. "Memory Limits for Windows Releases" http://msdn.microsoft.com/en-us/library/aa366778(VS.85).aspx Paul
From: Robert Baer on 4 Apr 2010 11:11
Paul wrote: > Jeff Strickland wrote: >> "gnu / linux" <rob.fruth(a)gmail.com> wrote in message >> news:b35c497d-ec86-4db3-9e9e-8b4aee2d09ac(a)e7g2000yqf.googlegroups.com... >> On Apr 2, 7:12 pm, "Jeff Strickland" <crwlrj...(a)yahoo.com> wrote: >>> "sandy58" <alecki...(a)googlemail.com> wrote in message >>> >>> news:84997128-2b8c-45dd-a19f-de07cf91fce7(a)10g2000yqq.googlegroups.com... >>> On Apr 2, 7:55 pm, "James D. Andrews" <jamesdandr...(a)att.net> wrote: >>> >>>> Do I need to use a 64-bit OS with 4GB RAM, or will 32-bit work? I was >>>> reading today that the 32-bit will only support 3GB. Don't know how >>>> true >>>> that is. >>>> I suppose it would be nice to know before I go and buy an OS. >>> 32-bit won't use 4gb ram. 3gb is about it. >>> 64-bit will use as much as you can get in. >>> >>> <JS> >>> I'm using all 4G of RAM in my machine. I have 32-bit XP Pro. >>> >>> </JS> >> >> 32 bit will use most all of the 4 GB >> >> >> >> <JS> >> That's my point. The person I was replying to said that only 3G is >> supported by 32-bit systems. >> >> </JS> >> > > This depends a lot, on the details. > > As JS mentioned via a link at the end of his posting, there is a > hardware feature called PAE, that maps 32 bit addresses to a 36 bit > physical address space. Intel processors and chipsets have had PAE > capability for some time. And PAE allows a 32 bit OS to address up to > 64GB of installed memory. (Modern PAE can support more than 36 bits, > so more is possible. For example, on modern AMD processors, it goes > to 40 bits.) > > It is possible that some early version of WinXP, still properly supported > PAE. But in later Service Packs, a bit was borrowed for something like NX > (no execute) bit. That was a security feature. At the same time, they > decided it would be fun to prevent PAE from accessing more than 4GB. > I'm a little fuzzy on the details. > > There is a discussion about this topic, here. This person hacked an MS > OS, to prove that more than 4GB can be addressed by a 32 bit OS. It works. > > http://www.geoffchappell.com/viewer.htm?doc=notes/windows/license/memory.htm > > > So, if the OS has PAE neutered, then indeed there might be only > 4GB of address space available via the 32 bit OS. From that, the > hardware devices (like the memory on the video card), has to be > addressable. And after all the addresses for the various hardware > busses have been assigned by the BIOS, the remainder is used to > provide access to the memory DIMMs. If you install 4GB worth of DIMMs, > and happened to use an old PCI video card with small resident memory, > you might see reported that you have 3.5GB free. (Bus address space > is assigned in 256MB chunks, and with PCI/AGP or PCI/PCI Express, > you might lose two chunks to start with. Once the actual hardware > rolls over that assignment, another chunk would be mapped in. So > the assignment process has a relatively coarse granularity.) > > If you install a couple Nvidia video cards in SLI, with 512MB of > memory on each card, and happen to have 4GB memory installed, > and have the neutered OS running, then the free memory reported > once the OS is running, could be as low as 2.75GB (someone reported > that, on an S939 board). Which negates the purpose of installing > that much memory to begin with. If you had a monster video setup, > you might be better off installing 2x1GB + 2x512MB sticks, for a > total of 3GB dual channel mode. And then, you'd still see the > 2.75GB free reported, and would only be losing 0.25GB. > > Or, you could use a 64 bit OS, and have it all. > > In terms of the memory configuration, a lot of people would choose > to use 2x2GB, as it may support a higher max operating frequency > for the DIMMs. And then take the loss, on whatever amount of memory > is inaccessible by the OS. Using a four stick configuration, might > not clock quite as high. > > The details are a bit fuzzy, as to whether there is a good reason > for PAE to not work on WinXP x32. But it would certainly push > sales of alternate OS solutions. (And no, WinXP x64 is not a good > choice. It was a little rough around the edges.) > > If you use PAE, one of the limitations would be, that a single > program could not use all the memory on the computer. If you > had 8GB of RAM installed, used a 32 bit OS, you would need > two programs, accessing 4GB each, to use all the memory. > There might even be further restrictions, as to the maximum > memory that any program or process could use (user/kernel split?). > So even if PAE was working, it is a less ideal situation than using a > 64 bit OS to solve the addressing limitations. But PAE > does have the advantage, that it has been available in hardware > for a long time. It is only now, that ordinary desktops > can easily reach those memory limits. > > http://en.wikipedia.org/wiki/Physical_Address_Extension > > "Windows XP Service Pack 2 and later, by default, on processors > with the no-execute (NX) or execute-disable (XD) feature, runs > in PAE mode in order to allow NX. The no execute (NX, or XD for > execution disable) bit resides in bit 63 of the page table entry > and, without PAE, page table entries on 32-bit systems have only > 32 bits; therefore PAE mode is required if the NX feature is to > be exploited. > > However, "client" versions of 32-bit Windows (Windows XP, Windows > Vista, Windows 7) limit physical address space to the first 4 GB > for driver compatibility and *licensing* reasons, even though these > versions do run in PAE mode if NX support is enabled." > > So that tells you, the limitation is artificial. > > There are some other things to consider, before making the OS choice. > For example, how much memory does the software you own, want to use ? > I have a copy of Photoshop, that won't go above 1.8GB on a 4GB system. > For the people that own large quantities of memory, I'd be interested > in what exactly they've been able to get out of it. I wasted a couple > hours on the topic and gave up (my machine is back to 2GB now). I > don't seem to have anything which is IMAGE_FILE_LARGE_ADDRESS_AWARE. > I could certainly run a couple different programs, to use the RAM, > such as some VPC2007 sessions. And that is the most likely thing > here, that would benefit from 4GB. For a lot of other stuff, 2GB > is enough for me. > > http://en.wikipedia.org/wiki/RAM_Limit > > A 64 bit OS, makes some of the issues more transparent. But does > not guarantee that a single program can use all available memory. > For example, if you have a 64 bit executable, running on a 64 bit > OS, that removes the limits. But other combinations could > still have limits, like running existing 32 bit programs on > a 64 bit OS. > > "Memory Limits for Windows Releases" > http://msdn.microsoft.com/en-us/library/aa366778(VS.85).aspx > > Paul What little i know and remember about PAE, you are absolutely correct. However, the software that allows the "higher 2GB" od the "full 4GB" for program access (at least in Win2K) is/was clunky and slow WRT direct and full ASM-type access. With 3GB installed (all the MB i had at the time would support), i was able to program access to near 2Gbytes of RAM without the use of PAE (for multi-million digit math routines). Te upper Gbyte was mostly empty, except for the OS and its support; a smaller part was in very low memory (guessing that was the 8-bit OS stuff). |