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QUAD2X4096-8500C5DF and Vista 32bit


bLuDrGn

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The kit will run with Vista but you will not detect 4096MB of memory in any 32-Bit OS. This is a limitation with any X86 system running a 32-Bit Operating System. The system will only recognize 4.0 Gig Bit of memory Max (Not Giga-Byte) and the other memory in your system will come off of the top, like memory in your Video card and or the cache in your CPU and network card. So for example if you have 4x 1024MB modules, Windows will see minus the cache in your CPU and the memory in your Video card So if you have a 256 Meg Video card it might show 3.2 Giga Byte of total memory. And with some MB's they will reserve some of the memory for PCI devices in the system so that number may drop to bellow 3.0 Gig of total memory. For a more detailed explanation, please refer to this Microsoft Knowledge Base Artice: http://support.microsoft.com/kb/929605/en-us.
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  • 2 weeks later...

Hey Ram Buy,

First off, I want to say that a lot of your stuff I read is Dead-on. There's often other stuff I read that you've written which increases my knowledge since I learn something I didn't know.

 

HOWEVER :-)

 

There's one thing I've read in two or three different threads that you've written, which makes me want to offer a correction. I think you have the correct 'goal' in mind, but the facts you offer don't add up to the assertion.

 

It's your description of 32bit and it's memory address limitations. Here's the correct way to describe the limits (since Giga-bit has nothing to do with it):

 

First and foremost, the 4GB limit memory limit is a limitation of the 32-bit Intel x86 processor architecture:

-The minimum addressable memory unit is 1 Byte (8 bits).

-Since 32 bit processors only have 32 address lines, the maximum amount of addresses which can be accessed are: 2^32 = 4,294,967,296.

-If you can address 2^32 memory locations that are 1 Byte wide, you can therefor address 2^32 *1 Byte = 4,294,967,296 Bytes of data = 4GB of addressable memory

 

Now, 32 bit Windows (XP or Vista) sits on top of the Intel 32-bit architecture. Windows can access all available RAM up to 4GB. However since, for years, no one ever had, nor needed, 4GB of RAM, Windows mapped Bios, Drivers and Video memory at the top of the 4GB address range and worked downward from there. Let's pretend you have 4GB of RAM installed, a 256MB Video card, a 64MB Sound Card and the system reserved 192 MB of RAM for Cache:

4096 MB - Top of memory address

- Sound Card memory map

4032 MB

- System Cache memory map

3840 MB

- Video Memory Map

3585 MB - Start of Video Memory Map

3584 MB - Top of System/user addressable RAM

- 3.5 GB or 3584 MB of user/sytem addressable RAM

0000 MB - Start of Memory addresses

 

Let's pretend you have the same system, except you only install 2GB of RAM:

 

4096 MB - Top of memory address

- Sound Card memory map

4032 MB

- System Cache memory map

3840 MB

- Video Memory Map

3584 MB - Start of Video Memory Map

- 1.5GB or 1532 MB of un-addressable since no physical device

or RAM is installed

2048 MB - Top of physical RAM installed in the system

- 2 GB or 2048 MB of user/sytem addressable RAM

0000 MB - Start of Memory addresses

 

Item's in purple above represent device memory mapped into the 32bit address space for System I/O or communication purposes.Item's in blue above represent the physical address memory space available to the System/OS/User as RAM.

Item's in black above represent address space that's not mapped.

 

32-bit Processor/OS conclusion:

In this example a system with 2GB installed will allow the OS/User to 'see' or utilize 2GB of RAM.

Installing 4GB of RAM will allow the OS/User to 'see' or utilize only 3.5GB of the installed ram, since .5GB or 512MB is reserved for mapping other physical hardware into the 4GB addressable limit.

 

 

This concept is exactly the the same for a 64bit OS(XP or Vista) and 64bit Processor combination. The difference is that the upper limit for addressable memory space on a 64bit system is 2^64 = 18,446,744,073,709,551,616 Bytes, which is 17,179,869,184 GB, which is 16,384 PB (PetaBytes). It will be a long time before they start making 4,096PB memory sticks....but that's why a they said about 1GB memory sticks 12 years ago....

 

--------------------------------------------------------------

RG, I hope this has been helpful and I certainly offer this with the best intentions, since I've learned a lot from your posts, I was hoping to add something in return.

 

Sincerely,

Gedd

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