Podcast
Questions and Answers
What does ROM stand for?
What does ROM stand for?
Read Only Memory
What does RAM stand for?
What does RAM stand for?
Random Access Memory
What does EPROM stand for?
What does EPROM stand for?
Erasable Programmable ROM
What does EEPROM stand for?
What does EEPROM stand for?
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What does DRAM stand for?
What does DRAM stand for?
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What does SIMM stand for?
What does SIMM stand for?
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What does DIMM stand for?
What does DIMM stand for?
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What is the purpose of Synchronous RAM (SDRAM)?
What is the purpose of Synchronous RAM (SDRAM)?
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What is a characteristic of Double-Data-Rate SDRAM (DDR SDRAM)?
What is a characteristic of Double-Data-Rate SDRAM (DDR SDRAM)?
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In a computer with N-bit address lines, it is capable of addressing _____ memory locations.
In a computer with N-bit address lines, it is capable of addressing _____ memory locations.
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Cache memory is positioned between normal main memory and the CPU.
Cache memory is positioned between normal main memory and the CPU.
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What is the function of memory in a computer system?
What is the function of memory in a computer system?
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Which of the following are common word lengths used to express memory capacity?
Which of the following are common word lengths used to express memory capacity?
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Access time (latency) refers to the rate at which data can be transferred into or out of a memory unit.
Access time (latency) refers to the rate at which data can be transferred into or out of a memory unit.
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As we move down the memory hierarchy, the access time ________ and the capacity ________.
As we move down the memory hierarchy, the access time ________ and the capacity ________.
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Match the memory characteristic with its description:
Match the memory characteristic with its description:
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Study Notes
Overview of Computer Architecture and Memory
- Course objectives: understand structure and function of different types of memories
- Topics covered: memory organization, memory types (ROM, SRAM, DRAM), memory chip, memory map, memory interfacing, cache memory
Memory System Overview
- Definition of memory: data storage module
- Memory characteristics: capacity, cost per bit, access time, transfer rate, physical characteristics (volatile/non-volatile, erasable/non-erasable)
- Ideal memory features: fast access time, high transfer rate, non-volatile, low power, high capacity, low cost per bit, in-system re-writable, fully-bit erasable
- Memory hierarchy: registers, cache, main memory, magnetic disks, tapes, optical disks
Memory Organization and Function
- Memory module: latch, flip-flop, register, memory chip (ROM, EPROM, EEPROM, FLASH, SRAM, DRAM), optical disc, magnetic disk, magnetic tape
- Flip-flop or latch memory cell: 1-bit memory cell, active low write signal, active low read signal
- Example: 4x8-bit memory using two 4x4-bit memory chips
- Memory chip requirements: address lines, data lines, enable signal, chip select signal, read signal, write signal
Memory Types
- Read Only Memory (ROM)
- Permanent storage
- Non-volatile
- Used in microprogrammed control unit and system programs (BIOS)
- Random Access Memory (RAM)
- Can both read data from and write data into the memory
- Volatile
- Types of ROM:
- Maskable ROM
- One-time programmable ROM (fuse ROM)
- EPROM (Erasable Programmable ROM)
- EEPROM (Electrically Erasable Programmable ROM)
- Flash memory
- Types of RAM:
- Static RAM (SRAM)
- Dynamic RAM (DRAM)
ROM
- Maskable ROM: data is 'wired in' during fabrication, very expensive for small runs
- One-time programmable ROM (OTP ROM): data can be written once by the user, useful for small production runs
- EPROM: can be erased by exposing to Ultra Violet (UV) light, entire memory is erased, off-system programming and de-programming
- EEPROM: can be written to many times while remaining in a system, writes require several hundred microseconds per byte
- Flash memory: similar to EEPROM, supports block erasures, faster erasures
DRAM
- Dynamic Random Access Memory (DRAM)
- Bits stored as charge in capacitors
- Charges leak, need refresh circuits
- Simpler construction, less expensive, slower, used for main memory
- Read and write operations: address line active, transistor switch closed, charge from capacitor fed via bit line to sense amplifier
SRAM
- Static Random Access Memory (SRAM)
- Bits stored as on/off switches
- No charges to leak, no need for refresh circuits
- More complex construction, more expensive, faster, used for cache memory
- 6T-SRAM cell compared to 1T-DRAM cell### Memory Types
- Random-access memory (RAM):
- Category: Read-write memory
- Erasure: Electrically, byte-level
- Write mechanism: Electrically
- Volatility: Volatile
- Read-only memory (ROM):
- Category: Read-only memory
- Erasure: Not possible
- Write mechanism: Masks
- Volatility: Nonvolatile
- Programmable ROM (PROM):
- Category: Read-mostly memory
- Erasure: Not possible
- Write mechanism: Electrically, byte-level
- Volatility: Nonvolatile
- Erasable PROM (EPROM):
- Category: Read-mostly memory
- Erasure: UV light, chip-level
- Write mechanism: Electrically
- Volatility: Nonvolatile
- Electrically erasable PROM (EEPROM):
- Category: Read-mostly memory
- Erasure: Electrically, byte-level
- Write mechanism: Electrically
- Volatility: Nonvolatile
- Flash memory:
- Category: Read-mostly memory
- Erasure: Electrically, block-level
- Write mechanism: Electrically
- Volatility: Nonvolatile
Memory Chip
- A memory chip contains an array of memory cells
- Each chip has a specific organization and size (e.g., 16 Mbits DRAM, 4Mx4bits)
Memory Module Organization
- A memory module is a group of chips mounted on a printed circuit board (PCB)
- Examples: Single Inline Memory Module (SIMM) and Dual Inline Memory Module (DIMM)
- A DIMM card can contain 16 chips of 64MBytes each
Memory Map/Interfacing
- Memory map: dividing the memory range into sections suited to specific roles (e.g., program section, data section, stack section)
- Memory interfacing: allows the CPU to read from and write into a location of a given memory chip
- Decoding: generating the chip select signal (CS) or chip enable (CE) signal
- Interfacing: connecting the data lines of the memory chip to the data bus, and the address lines to the address bus
Word vs. Byte Addressable Memory
- Word addressable memory: each address location stores one word of data
- Byte addressable memory: each address location stores one byte of data
- Most computer designs use byte addressable memory
Byte Ordering
- Little-endian: stores the least significant byte first (e.g., Intel X86 processors)
- Big-endian: stores the most significant byte first (e.g., Motorola and Sparc processors)
Cache Memory
- Cache memory: small, fast memory that stores recently used words from main memory
- Cache levels: Level-1 (L1), Level-2 (L2), and Level-3 (L3) caches
- Cache operation: CPU requests contents of memory location, checks cache, and retrieves data from cache or main memory
External Memory
- Magnetic disk: Hard Drive Disk (HDD), magnetic tape
- Optical disc: Compact Disc (CD), Digital Versatile Disc (DVD), Blu Ray
- Solid-state storage: Flash memory, Solid State Disk (SSD)
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Description
This quiz covers the concepts of Memory in Computer Architecture, including types, organization and management of memory. It's a part of EE321 course at University M’hamed Bougara of Boumerdes.
