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#1
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Confused about RAM #
When I checked BIOS, I confirmed that 4GB memory (2 GB x 2) was installed in
my computer. But when I looked at System Properties, 2.98 GB of RAM was shown. Could someone explain this discrepancy? Jorge |
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#2
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Confused about RAM #
A very common question. Try a web search with this as your search term...
windows doesn't show all 4GB of RAM For example: "Why doesn't Windows show all 4gigabytes of memory I have installed?" http://ask-leo.com/why_doesnt_window...installed.html --- Leonard Grey Errare humanum est Jorge Cervantes wrote: When I checked BIOS, I confirmed that 4GB memory (2 GB x 2) was installed in my computer. But when I looked at System Properties, 2.98 GB of RAM was shown. Could someone explain this discrepancy? Jorge |
#3
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Confused about RAM #
A very common question. Try a web search with this as your search term... windows doesn't show all 4GB of RAM For example: "Why doesn't Windows show all 4gigabytes of memory I have installed?" http://ask-leo.com/why_doesnt_window...installed.html --- Leonard Grey Errare humanum est Jorge Cervantes wrote: When I checked BIOS, I confirmed that 4GB memory (2 GB x 2) was installed in my computer. But when I looked at System Properties, 2.98 GB of RAM was shown. Could someone explain this discrepancy? Jorge |
#4
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Confused about RAM #
Thier's an answer for that,follow this link & read on.
http://support.microsoft.com/kb171793 If you want more info,go to : http://www.microsoft.com/technet Use search & type in info. "Jorge Cervantes" wrote: When I checked BIOS, I confirmed that 4GB memory (2 GB x 2) was installed in my computer. But when I looked at System Properties, 2.98 GB of RAM was shown. Could someone explain this discrepancy? Jorge . |
#5
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Confused about RAM #
Thier's an answer for that,follow this link & read on. http://support.microsoft.com/kb171793 If you want more info,go to : http://www.microsoft.com/technet Use search & type in info. "Jorge Cervantes" wrote: When I checked BIOS, I confirmed that 4GB memory (2 GB x 2) was installed in my computer. But when I looked at System Properties, 2.98 GB of RAM was shown. Could someone explain this discrepancy? Jorge . |
#6
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Confused about RAM #
In message , Andrew
E. writes: Thier's an answer for that,follow this link & read on. http://support.microsoft.com/kb171793 That gives "Sorry, but we couldn't find the page that you requested." .... "Are you looking for: q171793" ... "(171793) - This article describes the 4GT RAM Tuning feature of Windows NT Server Enterprise Edition (Windows NT Server/E) version 4.0." [] -- J. P. Gilliver. UMRA: 1960/1985 MB++G.5AL-IS-P--Ch++(p)Ar@T0H+Sh0!:`)DNAf ** http://www.soft255.demon.co.uk/G6JPG-PC/JPGminPC.htm for ludicrously outdated thoughts on PCs. ** Boss: We must maintain a sense of urgency. Speed is the key. We must be faster than the competition. Dilbert: Does that mean you'll sign the stuff that's been on your desk for a month? (Scott Adams, 1998-12-26) |
#7
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Confused about RAM #
In message , Andrew
E. writes: Thier's an answer for that,follow this link & read on. http://support.microsoft.com/kb171793 That gives "Sorry, but we couldn't find the page that you requested." .... "Are you looking for: q171793" ... "(171793) - This article describes the 4GT RAM Tuning feature of Windows NT Server Enterprise Edition (Windows NT Server/E) version 4.0." [] -- J. P. Gilliver. UMRA: 1960/1985 MB++G.5AL-IS-P--Ch++(p)Ar@T0H+Sh0!:`)DNAf ** http://www.soft255.demon.co.uk/G6JPG-PC/JPGminPC.htm for ludicrously outdated thoughts on PCs. ** Boss: We must maintain a sense of urgency. Speed is the key. We must be faster than the competition. Dilbert: Does that mean you'll sign the stuff that's been on your desk for a month? (Scott Adams, 1998-12-26) |
#8
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Confused about RAM #
Jorge Cervantes wrote:
When I checked BIOS, I confirmed that 4GB memory (2 GB x 2) was installed in my computer. But when I looked at System Properties, 2.98 GB of RAM was shown. Could someone explain this discrepancy? This is a hardware issue concerning the processor address space below the 4GB barrier and the inability of 32-bit Microsoft client operating systems to "see" the processor's address space above the 4GB barrier. It's a problem that is based on an older architecture design for memory addressing. In fact, your machine is using a bit more than 5GB of address space but Windows XP cannot see any of it above 4GB. Let's see if I can explain this in a few short paragraphs. The processor works with data, it brings in data, processes it and returns data. Every bit of data comes in to the processor from a memory address and every bit leaving the processor goes to a memory address. A 32-bit processor has 4,294,967,296 memory addresses. This is the processor's addressable memory range or the Address Space, with these memory addresses the processor can directly access four gigabytes of memory. So what's the problem? The processor has enough addresses for 4GB of RAM, why isn't it using all of it? The problem is that if the processor gave all the addresses to the RAM it would have none left for other things, anything and everything that needs to talk to the processor would have to do so through the RAM or the processor would have to dump RAM addresses to talk to other devices! Your computer is not only made up of RAM, the processor has to work with other hardware devices, it has to send and get data to and from some of those other devices. Remember, the processor gets and returns data to memory addresses, the 32-bit processor has a 4GB address range. For example, the BIOS and system board will reserve and use a bit less than 1 megabyte of address space directly at the processor, when the processor needs to talk with the BIOS or motherboard it will do so directly by using their reserved addresses, the addresses reserved by and given to the system board cannot be used by the RAM. This (oversimplified) example shows why a 32-bit processor cannot use all of the RAM when 4GB is installed. So now you may be thinking that 1 megabyte of memory addresses being lost to the system board is a far cry from what your Windows installation is seeing and reporting. Well, you see, most PCI devices can communicate directly with the processor. These devices also reserve exclusive memory addresses directly at the processor, if the video card needs to talk to the processor it will do so at its reserved addresses, the addresses where the processor is listening. Your other PCI devices like sound cards, controller cards and so on also reserve addresses directly at the processor, the processor can send and receive data directly to and from these devices. These devices can reserve a lot of address space, a high end sound card can reserve 100 megabyte or more of address space. A video card with 512MB of on board memory has to have a way of sending the data in that memory to the processor when needed, if all the memory addresses were used by RAM the processor would have none left to satisfy the needs of other devices. That is why addresses are reserved for exclusive use by the PCI devices, the addresses that are reserved for these devices are in turn not available for RAM addressing. The amount of memory address space used by these devices can be as little as a few hundred megabytes and, as with your computer, all the way up to 1GB and more. It is important to note that the other devices do not use RAM, they reserve or use addresses at the processor and in turn these addresses are not available for the RAM, the RAM is in fact deprived of the addresses and the RAM without address space goes unused. To overcome this address shortage problem (newer) Intel 32-bit processors make use of Physical Address Extensions (PAE) which widens the address width to 36-bits and greatly increases the available memory address space. The use of PAE and 36-bit addressing allows the processor to access 64GB of RAM, the RAM that was previously unaddressed can now be addressed. Newer 64-bit processors have an even wider address width which greatly increases the address space beyond the 64GB available to 32-bit PAE processors. The catch is that the PCI devices keep their addresses in the lower 4GB address range and the previously unavailable address space for the RAM is shifted *above* the 4GB arena and to access the RAM above the 4GB arena the 32-bit operating system has to fully support this PAE feature, if it doesn't it cannot access the RAM in the space above the 4GB boundary. Raymond Chen has explained this very well he http://blogs.msdn.com/oldnewthing/ar...14/699521.aspx Windows 2000 Professional, Windows 2000 Server, Windows XP 32-bits and Vista 32-bits do not make full use of this /PAE feature, they are unable to use RAM addressed above the 4GB boundary. You need Windows 2000 Advanced Server or better to be able to fully use this /PAE feature. Or you need to move to a 64-bit operating system which can access more than 4GB of RAM without the PAE "crutch". John |
#9
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Confused about RAM #
Jorge Cervantes wrote:
When I checked BIOS, I confirmed that 4GB memory (2 GB x 2) was installed in my computer. But when I looked at System Properties, 2.98 GB of RAM was shown. Could someone explain this discrepancy? This is a hardware issue concerning the processor address space below the 4GB barrier and the inability of 32-bit Microsoft client operating systems to "see" the processor's address space above the 4GB barrier. It's a problem that is based on an older architecture design for memory addressing. In fact, your machine is using a bit more than 5GB of address space but Windows XP cannot see any of it above 4GB. Let's see if I can explain this in a few short paragraphs. The processor works with data, it brings in data, processes it and returns data. Every bit of data comes in to the processor from a memory address and every bit leaving the processor goes to a memory address. A 32-bit processor has 4,294,967,296 memory addresses. This is the processor's addressable memory range or the Address Space, with these memory addresses the processor can directly access four gigabytes of memory. So what's the problem? The processor has enough addresses for 4GB of RAM, why isn't it using all of it? The problem is that if the processor gave all the addresses to the RAM it would have none left for other things, anything and everything that needs to talk to the processor would have to do so through the RAM or the processor would have to dump RAM addresses to talk to other devices! Your computer is not only made up of RAM, the processor has to work with other hardware devices, it has to send and get data to and from some of those other devices. Remember, the processor gets and returns data to memory addresses, the 32-bit processor has a 4GB address range. For example, the BIOS and system board will reserve and use a bit less than 1 megabyte of address space directly at the processor, when the processor needs to talk with the BIOS or motherboard it will do so directly by using their reserved addresses, the addresses reserved by and given to the system board cannot be used by the RAM. This (oversimplified) example shows why a 32-bit processor cannot use all of the RAM when 4GB is installed. So now you may be thinking that 1 megabyte of memory addresses being lost to the system board is a far cry from what your Windows installation is seeing and reporting. Well, you see, most PCI devices can communicate directly with the processor. These devices also reserve exclusive memory addresses directly at the processor, if the video card needs to talk to the processor it will do so at its reserved addresses, the addresses where the processor is listening. Your other PCI devices like sound cards, controller cards and so on also reserve addresses directly at the processor, the processor can send and receive data directly to and from these devices. These devices can reserve a lot of address space, a high end sound card can reserve 100 megabyte or more of address space. A video card with 512MB of on board memory has to have a way of sending the data in that memory to the processor when needed, if all the memory addresses were used by RAM the processor would have none left to satisfy the needs of other devices. That is why addresses are reserved for exclusive use by the PCI devices, the addresses that are reserved for these devices are in turn not available for RAM addressing. The amount of memory address space used by these devices can be as little as a few hundred megabytes and, as with your computer, all the way up to 1GB and more. It is important to note that the other devices do not use RAM, they reserve or use addresses at the processor and in turn these addresses are not available for the RAM, the RAM is in fact deprived of the addresses and the RAM without address space goes unused. To overcome this address shortage problem (newer) Intel 32-bit processors make use of Physical Address Extensions (PAE) which widens the address width to 36-bits and greatly increases the available memory address space. The use of PAE and 36-bit addressing allows the processor to access 64GB of RAM, the RAM that was previously unaddressed can now be addressed. Newer 64-bit processors have an even wider address width which greatly increases the address space beyond the 64GB available to 32-bit PAE processors. The catch is that the PCI devices keep their addresses in the lower 4GB address range and the previously unavailable address space for the RAM is shifted *above* the 4GB arena and to access the RAM above the 4GB arena the 32-bit operating system has to fully support this PAE feature, if it doesn't it cannot access the RAM in the space above the 4GB boundary. Raymond Chen has explained this very well he http://blogs.msdn.com/oldnewthing/ar...14/699521.aspx Windows 2000 Professional, Windows 2000 Server, Windows XP 32-bits and Vista 32-bits do not make full use of this /PAE feature, they are unable to use RAM addressed above the 4GB boundary. You need Windows 2000 Advanced Server or better to be able to fully use this /PAE feature. Or you need to move to a 64-bit operating system which can access more than 4GB of RAM without the PAE "crutch". John |
#10
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Confused about RAM #
On Tue, 19 Jan 2010 09:01:31 -0700, "Jorge Cervantes"
wrote: When I checked BIOS, I confirmed that 4GB memory (2 GB x 2) was installed in my computer. But when I looked at System Properties, 2.98 GB of RAM was shown. Could someone explain this discrepancy? All 32-bit client versions of Windows (not just Vista/XP/7) have a 4GB address space (64-bit versions can use much more). That's the theoretical upper limit beyond which you can not go. But you can't use the entire 4GB of address space. Even though you have a 4GB address space, you can only use *around* 3.1GB of RAM. That's because some of that space is used by hardware and is not available to the operating system and applications. The amount you can use varies, depending on what hardware you have installed, but can range from as little as 2GB to as much as 3.5GB. It's usually around 3.1GB. Note that the hardware is using the address *space*, not the actual RAM itself. If you have a greater amount of RAM, the rest of the RAM goes unused because there is no address space to map it to. -- Ken Blake, Microsoft MVP (Windows Desktop Experience) since 2003 Please Reply to the Newsgroup |
#11
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Confused about RAM #
On Tue, 19 Jan 2010 09:01:31 -0700, "Jorge Cervantes"
wrote: When I checked BIOS, I confirmed that 4GB memory (2 GB x 2) was installed in my computer. But when I looked at System Properties, 2.98 GB of RAM was shown. Could someone explain this discrepancy? All 32-bit client versions of Windows (not just Vista/XP/7) have a 4GB address space (64-bit versions can use much more). That's the theoretical upper limit beyond which you can not go. But you can't use the entire 4GB of address space. Even though you have a 4GB address space, you can only use *around* 3.1GB of RAM. That's because some of that space is used by hardware and is not available to the operating system and applications. The amount you can use varies, depending on what hardware you have installed, but can range from as little as 2GB to as much as 3.5GB. It's usually around 3.1GB. Note that the hardware is using the address *space*, not the actual RAM itself. If you have a greater amount of RAM, the rest of the RAM goes unused because there is no address space to map it to. -- Ken Blake, Microsoft MVP (Windows Desktop Experience) since 2003 Please Reply to the Newsgroup |
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