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Old 05-18-2011, 05:01 PM   #1
ThomasLMcLean
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System RAM and Linux


I am relatively new with PC configuration and Linux.

The Windows 32 bit OS only recognize less the 4 Gb of RAM, their 64 bit OS goes to 8 Gb. Do the Linux OS have similar limits? I am using Ubuntu 10.04, but I am interested in a general Linux answer.

Thanks;

T L
 
Old 05-18-2011, 05:11 PM   #2
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Hi Thomas,

Well that is the limitation which will be there whether you use Linux or Windows. If you have a 32 bit OS running on a 32 bit system the maximum RAM it can use is 4GB the reason being a 32 bit system can access only 2 to the power 32 memory locations at the same time. Whereas, a 64 bit system can access 2 to the power 64 memory locations at the same time and thus increasing the amount of RAM it can support. That is how system hardware works so I would say it is not an OS limitation instead hardware limitation or you can say hardware design.

So it does not matter if you are using 32 bit Windows OS or 32 bit Linux OS the limitation will remain the same.

Also if you are using 6 GB RAM on a 32 bit system then it will show you 6 GB in the properties but in the backend it will only use 4 GB and the rest 2 GB will be used as a page file or virtual memory.

A 64 bit system can go beyond 8 GB even.

Last edited by T3RM1NVT0R; 05-18-2011 at 05:14 PM.
 
Old 05-18-2011, 05:15 PM   #3
brianL
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You can recompile a 32-bit kernel with the HIGHMEM64G option enabled. That allows it to "see" 4 GB RAM or over. And Debian has a ready made bigmem kernel in the repositories.

Last edited by brianL; 05-18-2011 at 05:16 PM.
 
Old 05-18-2011, 05:25 PM   #4
acid_kewpie
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Quote:
Originally Posted by ThomasLMcLean View Post
I am relatively new with PC configuration and Linux.

The Windows 32 bit OS only recognize less the 4 Gb of RAM, their 64 bit OS goes to 8 Gb. Do the Linux OS have similar limits? I am using Ubuntu 10.04, but I am interested in a general Linux answer.

Thanks;

T L
Windows Server 2008 R2 Enterprise supports up to 2TB of memory. Slightly more than 8gb. That limit is purely arbitrary based on how much money you give to M$, but even then the "Standard" version still supports 32gb by default with the 8b limit being on a "crippled" Foundation edition.
 
Old 05-18-2011, 05:26 PM   #5
TobiSGD
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Just for clarification: Linux can use more than 4 GB RAM with a 32 bit kernel if PAE is enabled, but that is not very efficient.

The memory limits of 64 Bit Windows are artificial for marketing purposes, an example for different Windows 7 64 bit editions:
  • Starter: 2GB
  • Home Basic: 8GB
  • Home Premium: 16GB
  • Professional, Enterprise, Ultimate: 192GB
This is not the case in Linux, AFAIK.

Quote:
the rest 2 GB will be used as a page file or virtual memory.
Without PAE they will be not used at all.
 
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Old 05-18-2011, 05:35 PM   #6
T3RM1NVT0R
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Hi Tobi,

Yes you are right that it won't detect more than 4 GB RAM on a 32 bit system without PAE-Kernel.
 
Old 05-18-2011, 05:56 PM   #7
jefro
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There is no real use for a newbie to NEED a 64 bit OS.

I think I'd start with learning 32 bit versions and move up later if you need access to large amounts of ram.

For the most part there is no real advantage to using 64 bit OS's for most people.
 
Old 05-18-2011, 06:32 PM   #8
ThomasLMcLean
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System RAM and Linux

Thanks to all of you for the very interesting and informative answers. As I had suspected, this gets more complex as I get into it.

From what has been said here, there seems to be little point in using more then 4 Gb. of RAM with a 32 bit system. However, I see several places where 8 Gb of RAM are recommended, particularly for gaming systems. These seem to infer that the extra RAM will be used for cache and will be an aid to rapid video delivery. If this is so, I assume that the effectiveness of the extra RAM would depend upon how the software is written. I would appreciated some comments on this aspect of system design.

Another item that I have not fully understood: I find some of Asus' motherboards support 4 channels of RAM (they have 4 slots) and some support 2 channels. These motherboards are built around the H67 chip-set and 1155 socket. The Intel descriptions for Sandy Bridge CPU's indicate that the CPU's support 2 channels of RAM. I would normally get 2 channels and put 2 Gb into each. However, I can't help but to ask "What are the guys with 8 Gb and 4 channels thinking?" Could someone please explain what is going on here.

Thanks;

T L
On the Wet Coast in Full Sun.
 
Old 05-18-2011, 06:44 PM   #9
TobiSGD
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This is a misunderstanding. Having four slots for RAM doesn't mean that you have a four-channel memory controller. All systems with socket 1155 have only a dual-channel memory controller. If you put 4 modules of RAM in your machine each channel is driving 2 modules.
Having 8GB of RAM is helpful in some use cases, for example if you run multiple virtual machines or are working on very large datasets. In gaming it can help, but it depends on the game. I have seen a significant speed improvement in GTA 4 when I changed from 4 to 8GB, but in other games I didn't. If a software wants to benefit from such amounts of RAM it has to be compiles for a 64 bit OS, but most games are AFAIK compiled for 32 bit systems. Some games come with a 32 and 64 bit binary to benefit from 64 bit systems.
 
Old 05-18-2011, 06:53 PM   #10
T3RM1NVT0R
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Quote:
From what has been said here, there seems to be little point in using more then 4 Gb. of RAM with a 32 bit system. However, I see several places where 8 Gb of RAM are recommended, particularly for gaming systems. These seem to infer that the extra RAM will be used for cache and will be an aid to rapid video delivery. If this is so, I assume that the effectiveness of the extra RAM would depend upon how the software is written. I would appreciated some comments on this aspect of system design.
Yes the effectiveness of the extra RAM would depend upon how the software is written. As you know that a 32 bit system cannot use more than 4 GB as physical RAM so the usage of rest 4 GB will depend up the effectiveness of OS as how it can utilize the extra RAM to its best as extended memory.

Quote:
Another item that I have not fully understood: I find some of Asus' motherboards support 4 channels of RAM (they have 4 slots) and some support 2 channels. These motherboards are built around the H67 chip-set and 1155 socket. The Intel descriptions for Sandy Bridge CPU's indicate that the CPU's support 2 channels of RAM. I would normally get 2 channels and put 2 Gb into each. However, I can't help but to ask "What are the guys with 8 Gb and 4 channels thinking?" Could someone please explain what is going on here.
Are asking what guys with 8 GB RAM with 4 channels running on a 32 bit system thinking? Well it will depend upon the OS then as to which one they choose and which can get the maximum out of extra memory.

Usually I have seen gaming guys use graphic cards because that serves as a dedicated memory for graphics and takes load out of CPU making your gaming experience much smoother.

Also for home PCs I will favour AMD as they are must faster and better when it comes home PCs but on server side I will prefer Intel over AMD. So my ideal configuration for a gaming system will be AMD64+6GB RAM (more than enough atleast for me) + ATi Radeon graphic card :-)
 
Old 05-18-2011, 07:56 PM   #11
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Quote:
Originally Posted by T3RM1NVT0R View Post
Yes the effectiveness of the extra RAM would depend upon how the software is written. As you know that a 32 bit system cannot use more than 4 GB as physical RAM so the usage of rest 4 GB will depend up the effectiveness of OS as how it can utilize the extra RAM to its best as extended memory.
Assuming that you talk about Windows, Windows 32 bit is in no way capable of using more than 4GB RAM, not even as some kind of "extended memory", regardless how the applications are written.

Quote:
Well it will depend upon the OS then as to which one they choose and which can get the maximum out of extra memory.
An OS can use the given memory or not. It can't get a maximum out of it, it always has the maximum if it can address the RAM.

Quote:
Usually I have seen gaming guys use graphic cards because that serves as a dedicated memory for graphics and takes load out of CPU making your gaming experience much smoother.
Usually gamers use graphics cards because of the dedicated graphics chips that are much faster for that special purpose than the usual x86 CPU. They have dedicated memory on that cards because it is much faster that way than to address system RAM.

Quote:
Also for home PCs I will favour AMD as they are must faster and better when it comes home PCs
Wrong, currently Intel has the fastest CPUs for the desktop market.

Quote:
So my ideal configuration for a gaming system will be AMD64+6GB RAM (more than enough atleast for me) + ATi Radeon graphic card :-)
That is such a generic statement that it is truely pointless. A Sempron 140 with 6GB RAM and a Radeon HD 5450 (by the way, they are named AMD Radeon nowadays) is in no way a gaming system.
 
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Old 05-18-2011, 10:18 PM   #12
jefro
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For any system you(we) need to know some parameters.

A normal home system may need 16G or 256M ram. Your use would decide it.

I'd guess to say that a new linux user may very well need all they can fit on a board but most do not.


Ram can be used in a number of ways. One is to support an application. The application may have been written to handle large files. In that case more ram is better. Knowing the parameters again. This is where one might suggest games. To be honest games in linux are not anywhere as advanced as windows games.

Ram could be used to simulate a hard drive. Neat way in some cases to really speed up an application.

Ram could be used to host many applications at once. One noted above that virtual machines take up a lot of ram so for each one you'd have to dedicate some ram.
 
Old 05-18-2011, 10:37 PM   #13
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It comes down to this:
  1. Whether you have a 32-bit or 64-bit CPU/motherboard.
  2. Whether your version of Linux is compiled for 32-bit vs. 64-bit processors.
  3. Whether your version of Linux is compiled to support "large amounts of memory." (Rationale: There's no reason for it to be built with the expanded data-structures needed to support lots of memory if you don't have lots of memory...)

Most "distros" ship with several different kernels and will automagically detect what your system can do, then they will install the right one(s).
 
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Old 05-19-2011, 12:12 AM   #14
ThomasLMcLean
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I believe that Sundialsvcs has summed it fairly well. Adding PAE will save having to get a 64 bit OS.

Thanks everyone for the information.

T L
 
  


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