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Why only 3.25Gb?


mizi709

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hello.. i' just buying a new set of gaming pc, powered by corsair gaming memory CGM2X2G800 (2GB x 2 pieces).. but, in the computer information, it just state only 3.25Gb or RAM.. why? why not 4GB? wheres my another 750MB memory's gone? can anybody explain to me why? :confused:
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I am guessing you are using a 32 bit operating system? If so, that's why. 32 bit operating systems can't address all 4 gb of memory. Someone with more knowledge than me will explain this in more detail for you.
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http://www.houseofhelp.com/v3/showthread.php?t=63681

 

Let me clarify.

 

Your computer has many methods in which to use memory. There are memory storage and caches all over the motherboard. These devices contain some of the below method of storage:

 

* RAM

* ROM

* Cache

* Dynamic RAM

* Static RAM

* Flash memory

* Virtual memory

* Video memory

* BIOS

 

For example, your sound, video, keyboard, chipset caches, I/O controller (IDE, SATA, etc) caches . . . Now these device with discrete and cache RAM need to have their "Addresses" so that the computer knows where they are in order to query and access them.

 

You computer also has System Resource Memory. Consider this as an index of addresses that tell the computer where everything is for access as mentioned above. The computer needs to know that a certain boundary of addresses will contain certain functions to perform when commanded.

 

Memory-mapped devices (such as your video card) will use some of that physical address space, as will the BIOS ROMs. After all the non-memory devices have had their say, there will be less than 4GB of address space available for RAM below the 4GB physical address boundary. Now a 32bit Operating system such as Windows XP 32bit and VISTA 32bit have the ability to access 2^32 bits = 4GB. Now if you have an 8800GTX with 768MB of DRAM, then that memory must be addressed in the space of the 4GB and you lose some of the system dram to the addressing. This continues with all other devices, leaving you with less than the 4GB. Since Windows can address up to 4GB, then with 3GB, there will be the 3 --> 4GB mapping so you should not lose that DRAM with 3GB unless your devices demand it. For example, SLi with 2 X 8800GTX 768MB will certainly take away from even the 3GB. Since you have a low discrete video memory amount you end up with more memory on your 32Bit system than those with more video RAM.

 

If you had a 2 GB system, then the video memory addressing is done in the discrete video card DRAM.

 

In your system, the Video card ROM is accessed by the CPU and 1.5GB of DRAM is seen. There is no addressable space since you are at the 4GB plateau level. Thus the CPU reserves 1.5GB of that 4GB. In a 64bit OS, the 4GB is like the 2GB is in a 32bit OS and the CPU just addresses the Video cards discrete DRAM above the 4GB level. On a 64bit OS with 8GB, the Video cards discrete DRAM is addressed above the 8GB.

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thanks a lot Derek... i'm trying to understand what are you xplaining.. so, because i'm using 32 bit of win xp pro, my ram is gone rite? how do i recover back my "lost" ram (750 mb)? sorry cause asking question like this.. i'm a noob about this.. huhuh...:p:
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i see... if i'm using 64bit os, i'll use the entire ram.. but i heard a rumors that saying 32 bit os is better than 64 bit os in terms of compatibility of drivers, 3rd party software, games and so on.. is that correct?
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i see... if i'm using 64bit os, i'll use the entire ram.. but i heard a rumors that saying 32 bit os is better than 64 bit os in terms of compatibility of drivers, 3rd party software, games and so on.. is that correct?

No, this is not correct. There were some issues relating to older software, older peripherals, etc that related to XP vs Vista but, it had nothing to do with 32bit vs 64bit.

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I find Vista 64bit SP1 to be a bit slow on boot, but other than that, it is fine system and plays all my games. If you have a marginal system in terms of speed, then I advise XP-32 and just use the 3.25GB. Then when Windows 7 is released you can make the transition to 64bit. It looks as though Vista can be considered like Windows Millenium Edition. A short term system to be used to allow software to catch up and hardware to be updated via timed attrition. Also a bit of a cash grab which M$ is certainly known for doing.
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