1. Memory and Storage Chapter 9

2. Memory Memory ( from programmer’s point of view): Temporary storage to hold data as well as programs. An Architect views memory as a solid state digital device that provide storage for data values. When an architect designs memory two key choices: - Technology - Organization Technology: properties of the underlying hardware mechanisms used to construct the memory systems. Organization: the way the underlying technology is used to form a working system.

3. Characteristics Of Memory Technologies Memory technology is characterized by several issues: -Volatile or nonvolatile: -Random or Sequential : -Primary or Secondary -Read-Write or Read-only: Read-Write: The values in the memory can be accessed or updated at any time. Read-only: The memory can be accessed but not changed. Different forms of ROM are: PROM : allows data values are burnt on the chip using high voltage, can be entered only once. EEPROM : values can be altered, but takes longer time than reading them. Flash ROM is a variant of EEPROM.

4. Concept of Memory Hierarchy Memory which has the highest performance characteristics is most expensive. The set of technologies should be arranged in a conceptual memory hierarchy. Architect selects the highest performance (costly)memory to be in smallest size. Ex: an architect selects a small number of general purpose registers and large amount of secondary memory. The levels of memory in a computer. From fastest to slowest speed, they are: 1. CPU registers 2. L1 cache 3. L2 cache 4. Main memory 5. Virtual memory 6. Disk

5. Instruction And Data Store The modern computer systems place program and data in a single memory(Von Neumann Architecture). The instructions and data are stored as separate stores to enhance performance. Instruction Store: - Memory used to store program. -Its needs higher performance, high speed instructions are designed to operate on values in general purpose registers rather than in memory. -An instruction is fetched every clock cycle. Data Store: -Memory used to store Data. -This is less active than the Instruction store. - Data values may also be a part of the instruction itself (immediate reference)

6. Key Points Memory Technology & Organization Memory Hierarchy Instruction & Data Store