الذاكرة الرئيسية (ملف شامل)

Main Memory
By Noor Kadhum
Architecture For 3rd Stage
Computer Science
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In the first lecture, we learned about the first level in the hierarchy of memory - registers – they are the only type of memory that resides inside the processor .
This lecture is dedicated to the study of another level in the hierarchicy. The main memory is the central storage unit in computer. It is relatively large and fast memory used to store programs and data during the computer operation.
Random Access Memory(RAM)
Integrated circuit RAM chips are available in two possible operating modes:
1- Static RAM : consists essentially of internal flip-flops that store the binary information. The stored information remains valid as long as power is applied to the unit. The static RAM is easier to use and has shorter read and write cycles.

2- Dynamic RAM: stores the binary information in the form of electric charges that are applied to capacitors(متسعات). The capacitors are provided inside the chip by MOS transistors. The charge on the capacitors tends to discharge with time and the capacitors must be periodically recharged by refreshing the dynamic memories. The dynamic RAM offers reduced power consumption and larger storage capacity in a single memory chip.