System setup recognises new memory but windows and DXDIAG does not!

[davesayz]

Dear All,

 

Just bought the 2GB Corsair value select 533mhz module. I installed it fine and booted up. I got the little beep saying new memory installed and selected F2 to go to the system set up. All was well and it showed I now had 4GB memory (previously 2GB) running at 533mhz. When I exited setup and went into windows vista the startup stuff showed I only had 3.00GB memory AAAHHH. I also ran dxdiag and this also came up as 3GB. My computer should run perfectly on 4GB RAM but it doesnt seem to recognise that its there. This is a problem right as it wont use all the available RAM ? Could it be anything to do with the fact that I had previously fiddled with the virtual memory settings?

If anyone could help it would be much appreciated.

 

Thanks

 

Dave

[DerekT]

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 the 3GB.

 

Hope this helps to clarify things a bit. If you move to a 64bit OS you will have all the 4GB to address.

[davesayz]

So basically what your saying is that the 4GB memory is still there but it only registers as 3GB because certain devices are using it ? I thought that graphics cards had their own memory in built hence GTX has 768mb etc. I do now understand why my geforce 7300LE somehow has magically shot up to 1400mb memory. Does it need all this ?

Thanks for clarifying a bit but im still not sure if its a good thing or a bad thing.

You say that on a 64 bit OS i can address 4GB RAM what does that mean.

 

Thanks

 

Dave