4GB of memory can only be displayed in the 32-bit system for about 3GB reasons

Original address: http://bbs.51cto.com/viewthread.php?tid=875012&extra=&page=1

1.4GB of memory in 32-bit system can only display the reason of about 3GB

The first reason will only "eat" a small portion of your memory

As we all know, in the computer binary conversion relationship is 1GB=1024MB, the actual production, the hardware manufacturer's conversion unit is 1GB=1000MB, when the computer manufacturer tells you that your computer memory is 1GB, in fact, your memory is 1000MB, system recognition, With 1000 for 1024, it will show that your memory is 0.976GB, the same as you installed 4G of memory, the system will show that your memory is 3.9GB. This is not a hardware vendor that deceives you.

The second reason may "eat" a significant portion of your memory

Memory (RAM, that is, your system's total addressing space) = Memory bar (physical memory, your memory bar is 4GB) +bios memory + cache + RAM +...,,32 bit of the address space of the computer is 2 of the 32 square, that is 4G, the system will this 4GB addresses allocated to the memory bar, cache, video memory, Hardware and so on.


The system allocates the address space to have the priority, the BIOS memory, the CPU cache, the memory of each hardware, the video card of the RAM, and so on, their priority is higher than the physical memory (that is, the memory bar), so the system first allocates the address space to the BIOS memory, CPU cache, the memory of each hardware, video card Finally, the remaining addressing space is allocated to the memory bar. For example, if your video card has 500MB, then the memory that can be allocated is only left 4GB-0.5GB=3.5GB.

The equivalent of 1000 residents in a street, but the house number is only 800, so there are 200 residents did not have access to the house number, but the 200 residents did not disappear.


If you install 4G memory on a 32-bit computer according to the priority relationship, you can only use more than 3G of memory space, because the previous hundreds of MB of space is given to each hardware (including video memory), 4GB of memory is only 3.31GB of which the address space is obtained, at which point you can only see the portion of the memory that obtained the address space (see.)



If it is 2G of memory, because the computer itself is addressing the 4G, the front hundreds of MB to the hardware, still have more than 3G of address space, 2G memory bar can fully obtain the 2G address space, you will be able to see the 2G memory bar
See

2. Theory of conversion and 32-bit cracking principle

About the 64-bit computer addressing ability, is the X64 architecture, theoretically X64 architecture complete addressing capacity of 2^64, that is, the maximum addressing capacity of 18446744073709551616, is equal to 16384GB, is capable of 16TB of memory, This is mainly to see whether the computer physical addressing architecture is not limited. At present, Intel and AMD desktop-level 64-bit processing maximum addressing capacity is only 128GB, only the server's processor to support 16TB of memory.
Then 32-bit system how to achieve the so-called more than 4G memory hack, the principle is very simple, now the CPU is basically 64-bit processor, that is, the hardware is not 4GB identification problem, the crack is the application of 64-bit system addressing principle, to open the 32-bit system to more than 4G memory limit. And the more memory is used as ramdisk to use, that is, the cache disk, in Windows under the software will produce temporary files, then he is the temporary files of these software products are moved to Randisk, and not to write to disk. It does increase the speed of the system at some point. But it is not true that systems and software use 64-bit systems and software addressing, still 32-bit addressing. If you apply this hack to a pure 32-bit CPU, try again if he can turn on the so-called Super 4G memory hack.
If you really want to effectively allocate more than 4G of memory to the system, it is recommended to use a 64-bit system, only 64-bit systems can natively support more than 4G of memory addressing.
There are many people on the 64-bit system has some understanding of the error, that 64-bit system can not use 32-bit software, it is wrong, in the WIN7 32-bit system can operate normally software, in the 64-bit system also basically does not have compatibility problems, in addition to anti-virus software, System optimization software and some professional software (but professional software basically has 64-bit version, such as AutoCAD, etc.). The only difference between running 32-bit software under a 64-bit system is that 32-bit software is still a 32 addressing mechanism.

4GB memory bars can only be displayed in the 32-bit system for about 3GB reasons (RPM)