Memory support for 32-bit and 64-bit systems

The author's earliest notebook is HP CQ45-M02TU, the memory is only 2G (DDR3_1333MHZ), and the WIN7_32 bit operating system is installed. It has been running slowly recently, improving performance by upgrading memory. Online purchase of a 2G same frequency memory, after installation, start the system, press WIN+PauseBreak, memory display as 4G, available memory is only 2.66G, the other more than 1G can not be used.

Theoretically, WIN7_32-bit systems support up to 4G memory, while 64-bit systems support more than 4G memory. In fact, my physical memory has increased to 4 gigabytes, while the WIN7_32 bit system only recognizes 2.66 gigabytes, which is obviously different from the theory. Later, I reinstalled the WIN7_64 bit system, showing 4 gigabytes of memory and 3.9 gigabytes of available memory, which shows that the size of the memory needs the support of the operating system.