Nonvolatile memories DRAM and sraM are volatile memories Lose information if powered off Nonvolatile memories retain value even if powered of Generic name is read-only memory(Rom Misleading because some RoMs can be read and modified Nonvolatile:非易失的
16 Nonvolatile memories • DRAM and SRAM are volatile memories – Lose information if powered off. • Nonvolatile memories retain value even if powered off – Generic name is read-only memory (ROM). – Misleading because some ROMs can be read and modified. Nonvolatile: 非易失的
Nonvolatile memories Types of ROMs Programmable ROM(PRom) Erasable programmable Rom(EProm Electrically erasable PROM(EEPROM) Flash memory Firmware Program stored in a rom Boot time code, BIOS(basic input/output system raphics cards disk controllers
17 Nonvolatile memories • Types of ROMs – Programmable ROM (PROM) – Erasable programmable ROM (EPROM) – Electrically erasable PROM (EEPROM) – Flash memory • Firmware – Program stored in a ROM • Boot time code, BIOS (basic input/output system) • graphics cards, disk controllers
Bus Structure Connecting CPU and memory a bus is a collection of parallel wires that carry address, data, and control signals Buses are typically shared by multiple devices
18 Bus Structure Connecting CPU and memory • A bus is a collection of parallel wires that carry address, data, and control signals • Buses are typically shared by multiple devices
Bus Structure Connecting CPU and memory P464 CPU chip register file ALU 4) system bus memory bus 2) main bus interface bridge memory
19 Bus Structure Connecting CPU and memory P464 main memory I/O bridge bus interface ALU register file CPU chip system bus memory bus 1) 2) 3) 4) 5)
Memory read transaction(1)Figure 6.7 P465 CPU places address a on the memory bus register file Load operation movl A, eax %eax main memory lo bridge 0 A bus interface X
20 Memory read transaction (1) Figure 6.7 P465 • CPU places address A on the memory bus ALU register file bus interface A 0 x A main memory I/O bridge %eax Load operation: movl A, %eax