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Maximum RAM for XP Pro 32-bit SP2
Hi -
My motherboard supports 16 gig RAM. I'm currently running 4 gig (this particular motherboard has 4 slots per processor so I'm at 2 gig per processor). The OS is reporting 2.75 gig when I right click on "my computer" because of a "memory hole" set up automatically in BIOS. I am using the /pae for NUMA and SiSoft Sandra shows it to be working. I just ordered 2 gig more so I would have a total of 3 gig per processor. I then heard that Windows XP Professional 32-bit w/SP2 is limited to "4 gig *physical address space*" (as opposed to pre SP2 supporting "4 gig of *RAM*"). Article he http://www.microsoft.com/whdc/system...AE/pae_os.mspx Now my question is: does that mean it will handle 4 gig per processor? Or just 4 gig total? I'm wondering if the memory hole is considered before or after that 4 gig ceiling and if the way my RAM is separated by processor makes any difference. I suppose, if I'm lucky, Windows will just ignore the extra RAM and report/use exactly 4 gig after memory hole, etc. ... until I make the jump to Vista. Of course, if I'm *real* lucky I'll find Windows XP SP2 will see and use all of my 6 gig minus the 1.25 gig memory hole so it will report 4.75 gig but I doubt that will be the case. -- Scotter Tyan Thunder K8WE Dual Opteron 252s @ 2.6ghz 4 gig DDR400 RAM XFX 7800 GTX 256 500 gig SATA2 Hitachi Dual 24" Dell LCDs 550W power supply |
#2
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Maximum RAM for XP Pro 32-bit SP2
On Tue, 31 Jan 2006 13:33:32 +0000, Scotter wrote:
Hi - My motherboard supports 16 gig RAM. I'm currently running 4 gig (this particular motherboard has 4 slots per processor so I'm at 2 gig per processor). The OS is reporting 2.75 gig when I right click on "my computer" because of a "memory hole" set up automatically in BIOS. I am using the /pae for NUMA and SiSoft Sandra shows it to be working. I just ordered 2 gig more so I would have a total of 3 gig per processor. I then heard that Windows XP Professional 32-bit w/SP2 is limited to "4 gig *physical address space*" (as opposed to pre SP2 supporting "4 gig of *RAM*"). Article he http://www.microsoft.com/whdc/system...AE/pae_os.mspx Now my question is: does that mean it will handle 4 gig per processor? Or just 4 gig total? I'm wondering if the memory hole is considered before or after that 4 gig ceiling and if the way my RAM is separated by processor makes any difference. I suppose, if I'm lucky, Windows will just ignore the extra RAM and report/use exactly 4 gig after memory hole, etc. ... until I make the jump to Vista. Of course, if I'm *real* lucky I'll find Windows XP SP2 will see and use all of my 6 gig minus the 1.25 gig memory hole so it will report 4.75 gig but I doubt that will be the case. I can't tell you much about Windows because I use Linux but I can tell you about how to deal with the memory hole. In your BIOS you should find an option called Memory Hole Remapping, turn it on. I have 4G on my 4400+ system and with Memory Hole Remapping off Linux only sees 3.5G, with it on it sees all 4G. As for seeing more than 4G with Windows XP Pro, there is a good chance that it's not possible. The x86 has a number of different memory mapping options. 32 bit Linux kernels can be compiled to support 1G, 4G or 64G of RAM. I would be willing to place a small wager that XP Pro uses the 4G memory map option and that XP Server uses the 64G option. In either case you'll be limited to 2 or 3G per process depending on how MS decided to divide up the 32 bit address space, someone who is more Windows savvy then me can tell you which it is. If you really what to have 6G of RAM in the system you should upgrade to 64 bit XP. |
#3
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Maximum RAM for XP Pro 32-bit SP2
"Scotter" wrote in message ... Hi - My motherboard supports 16 gig RAM. I'm currently running 4 gig (this particular motherboard has 4 slots per processor so I'm at 2 gig per processor). The OS is reporting 2.75 gig when I right click on "my computer" because of a "memory hole" set up automatically in BIOS. I am using the /pae for NUMA and SiSoft Sandra shows it to be working. I just ordered 2 gig more so I would have a total of 3 gig per processor. I then heard that Windows XP Professional 32-bit w/SP2 is limited to "4 gig *physical address space*" (as opposed to pre SP2 supporting "4 gig of *RAM*"). Article he http://www.microsoft.com/whdc/system...AE/pae_os.mspx Now my question is: does that mean it will handle 4 gig per processor? Or just 4 gig total? Total. Remember though this is physical address space, not virtual address space, which can be larger. I'm wondering if the memory hole is considered before or after that 4 gig ceiling and if the way my RAM is separated by processor makes any difference. I suppose, if I'm lucky, Windows will just ignore the extra RAM and report/use exactly 4 gig after memory hole, etc. ... until I make the jump to Vista. Of course, if I'm *real* lucky I'll find Windows XP SP2 will see and use all of my 6 gig minus the 1.25 gig memory hole so it will report 4.75 gig but I doubt that will be the case. You need XP 'server'. You also should probably use the /3GB switch, or the individual applications will be limited to a maximum of a 2GB virtual memory space (not address space though - important difference). Unfortunately, PAE brings with it some extra costs (the size of the PTE entries has to grow). It is this growth, that Pro does not support. Best Wishes |
#4
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Maximum RAM for XP Pro 32-bit SP2
In article ,
Roger Hamlett wrote: "Scotter" wrote in message . .. Hi - My motherboard supports 16 gig RAM. I'm currently running 4 gig (this particular motherboard has 4 slots per processor so I'm at 2 gig per processor). The OS is reporting 2.75 gig when I right click on "my computer" because of a "memory hole" set up automatically in BIOS. I am using the /pae for NUMA and SiSoft Sandra shows it to be working. I just ordered 2 gig more so I would have a total of 3 gig per processor. I then heard that Windows XP Professional 32-bit w/SP2 is limited to "4 gig *physical address space*" (as opposed to pre SP2 supporting "4 gig of *RAM*"). Article he http://www.microsoft.com/whdc/system...AE/pae_os.mspx Now my question is: does that mean it will handle 4 gig per processor? Or just 4 gig total? Total. Remember though this is physical address space, not virtual address space, which can be larger. Not with win/32. Virtual address space is the maximum segment size and in 32 bit windows the user space is 31 bits/2GB inless you play with the /3GB switch, which only brings it up to 3GB. -- a d y k e s @ p a n i x . c o m Don't blame me. I voted for Gore. |
#5
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Maximum RAM for XP Pro 32-bit SP2
"Al Dykes" wrote in message ... In article , Roger Hamlett wrote: "Scotter" wrote in message .. . Hi - My motherboard supports 16 gig RAM. I'm currently running 4 gig (this particular motherboard has 4 slots per processor so I'm at 2 gig per processor). The OS is reporting 2.75 gig when I right click on "my computer" because of a "memory hole" set up automatically in BIOS. I am using the /pae for NUMA and SiSoft Sandra shows it to be working. I just ordered 2 gig more so I would have a total of 3 gig per processor. I then heard that Windows XP Professional 32-bit w/SP2 is limited to "4 gig *physical address space*" (as opposed to pre SP2 supporting "4 gig of *RAM*"). Article he http://www.microsoft.com/whdc/system...AE/pae_os.mspx Now my question is: does that mean it will handle 4 gig per processor? Or just 4 gig total? Total. Remember though this is physical address space, not virtual address space, which can be larger. Not with win/32. Virtual address space is the maximum segment size and in 32 bit windows the user space is 31 bits/2GB inless you play with the /3GB switch, which only brings it up to 3GB. Even /3GB, won't change this, unless the application supports this (needs 'image file large address aware'). However, remember that an application, does not have to run in a single address space. If an application is multi-threaded, each thread can have a 2GB address space. I have a couple of applications that do this, and use much more than 4GB. Best Wishes |
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Maximum RAM for XP Pro 32-bit SP2
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#7
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Maximum RAM for XP Pro 32-bit SP2
On Fri, 03 Feb 2006 00:01:47 -0500, Toshi1873 wrote:
In article , says... I can't tell you much about Windows because I use Linux but I can tell you about how to deal with the memory hole. In your BIOS you should find an option called Memory Hole Remapping, turn it on. I have 4G on my 4400+ system and with Memory Hole Remapping off Linux only sees 3.5G, with it on it sees all 4G. Interesting... I'll have to remember to look at my Asus A8V BIOS on the linux box with 4GB of RAM (Linux is seeing 3.5GB). And I'm even running a 64bit kernel. On my WinXP Pro box, I simply took it from 1GB to 3GB because I had only originally put in 2x512MB (and added 2x1GB). So I've not used any WinXP boxes with more then 3GB yet. WinXP sees and uses all 3GB (PerfMon reports 3145196KB total memory). With 3G there is no memory hole problem so it doesn't matter what state the BIOS is in. The IOMMU is normally mapped to the high part of the 4G memory space which was never a problem in the past. Now that 4G of RAM is possible a change is needed. Both the BIOS and the kernel need to be able to handle the new scheme correctly. In the BIOS you have to turn on Memory Hole Remapping, on my MSI K8N Neo4 the latest BIOS has two options for this, hardware remapping and software remapping. As far as I can tell it doesn't make a difference which one you use. The previous rev of the BIOS only had Software Memory Hole Remapping. The second part of the equation is the kernel. The kernel has to be able to locate the IOMMU. The 2.6.13.x and 2.6.15.x kernels work fine, the 2.6.14.x kernels don't. Some bug in the IOMMU code was introduced into the 2.6.14.x kernels that caused them to panic when Memory Hole Remapping was enabled. The bug was fixed in 2.6.15 which is what I'm currently running. |
#8
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Maximum RAM for XP Pro 32-bit SP2
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