1. COMPUTER SCIENCE Data Representation and Machine Concepts Section 1.2 Instructor: Lin Chen August 2013

2. 1.2 Main Memory 1 Data Storage Memory Organization Measuring Memory Capacity

3. Memory Organization 1.2 Main Memory Computer Architecture Output Input

4. Memory Organization 1.2 Main Memory Memory consists of units Each unit is called a cell Cell

5. Memory Organization 1.2 Main Memory Memory consists of units Each unit is called a cell Cell 0 Cell 1 Cell 2 Cell 3 Cell 4 Cell 5 … …

6. Memory Organization 1.2 Main Memory Memory consists of units Each unit is called a cell Cell 0 Cell 1 Cell 2 Cell 3 Cell 4 Cell 5 … … Each cell contains 8 bits, called 1 byte 8 bits = 1 byte

7. Memory Organization 1.2 Main Memory Memory consists of units Each unit is called a cell Cell 0 Cell 1 Cell 2 Cell 3 Cell 4 Cell 5 … … 10111010 76543210 Index High-order end Low-order end Most significant bitLeast significant bit

8. Memory Organization 1.2 Main Memory Save content into the memory … Address

9. Memory Organization 1.2 Main Memory Save content into the memory … Address

10. Memory Organization 1.2 Main Memory Save content into the memory … Address

11. Memory Organization 1.2 Main Memory RAM A random-access device, allows stored data to be accessed directly in any random order Read number from address 03 Return 10011001 Write 10010001 to address 02

12. Memory Organization 1.2 Main Memory DRAM (Dynamic Random Access Memory) Each bit of data is stored in a separate capacitor The capacitor charge need refresh periodically Responds as quickly as possible to changes in control inputs SDRAM (Synchronous DRAM) wait for a clock signal before responding to control inputs Only one word of data is transmitted per clock cycle DDR Two words are transmitted per clock cycle http://en.wikipedia.org/wiki/Synchronous_dynamic_random-access_memory

13. 1.1 Bits and Their Storage 32-bits system and 64-bits system Measuring Memory Capacity KB 10 bits MB 20 bits GB 2 30 = 1024 MB20 bits TB 2 40 = 1024 GB20 bits 32 bits physical address or 64 bits physical address 8 bit address (Hexadecimal) 2 8 bytes kilo byte mega byte giga byte tera byte

14. 1.1 Bits and Their Storage Boolean Operations Questions: What is the memory in your notebook, SDRAM or DDR, DDR2, DDR3? What is the transmit speed of your memory? What is the capacity of your memory? What is your CPU frequency?