Week 6 - Computer Memory and Storage PDF

Computer Systems Architecture AICT023–4–1 – CA & Version VE1 Week 6 Computer Memory and Storage  Topic & Structure of the Lesson Memory - Types of Computer Memory Memory Hierarchy – Registers –...

Computer Systems Architecture AICT023–4–1 – CA & Version VE1 Week 6 Computer Memory and Storage  Topic & Structure of the Lesson Memory - Types of Computer Memory Memory Hierarchy – Registers – Cache Memory – Main Memory – Secondary Storage Types of Semiconductor Memory Memory Capacity Memory Organization AOCT004-4-1 CSA Memory Organisation SLIDE 2  Learning Outcomes At the end of this session, you should be able to: 1. Explain memory and its hierarchy the implementation in a computer system 2. Discuss different types of semiconductor memory 3. Calculate memory capacity of a given scenario 4. Explain memory organisation and relate it with CPU instruction processing cycle AOCT004-4-1 CSA Memory Organisation SLIDE 3  LEARNING OUTCOME 1 MEMORY Explain memory and its hierarchy the implementation in a computer system AOCT004-4-1 CSA Memory Organisation SLIDE 4  What is a Computer Memory?  Its very important part of computer system. There are various units which are used to measure computer memory.  Memory is combination of memory cells. Each cell length is 8 bit.  Every data stores in computer memory follows bit data such as 0’s and 1’s. AOCT004-4-1 CSA Memory Organisation SLIDE 5  Types of Computer Memory AOCT004-4-1 CSA Memory Organisation SLIDE 6  Types of Computer Memory (cont.) I. Secondary Memory II.Primary Memory a)RAM i. SRAM ii. DRAM b)ROM i. PROM ii. EPROM c)Hybrid i. EEPROM ii. NVRAM iii. Flash Memory d)Cache Memory e)Virtual Memory AOCT004-4-1 CSA Memory Organisation SLIDE 7  Memory Hierarchy The hierarchy design are divided into 2 main types: 1.Internal Memory or Primary Memory Comprising of Main Memory, Cache Memory & CPU registers. Directly accessible by the processor. 2. External Memory or Secondary Memory Comprising of Magnetic Disk, Optical Disk, Magnetic Tape etc. (peripheral storage devices) Accessible by the processor via I/O Module. AOCT004-4-1 CSA Memory Organisation SLIDE 8  Memory Hierarchy (cont.) AOCT004-4-1 CSA Memory Organisation SLIDE 9  Memory Hierarchy (cont.) AOCT004-4-1 CSA Memory Organisation SLIDE 10  Memory Hierarchy – Registers Register is a small permanent storage location within a CPU. The data not stores permanently. The purpose of registers store or hold data, information and address temporarily. The size of registers always in bit or in byte There are two types of registers such as General Purpose Register and Special Purpose Register AOCT004-4-1 CSA Memory Organisation SLIDE 11  Memory Hierarchy – Cache Memory One of the fastest memory called as Cache memory. It resides between CPU and main memory. It stores all frequently used data. Once the computer gets into off then the cache memory will be cleared automatically. Mainly it helps the CPU to get access of data quicker. Nowadays, modern computer system supports with L1, L2 and L3 caches. AOCT004-4-1 CSA Memory Organisation SLIDE 12  Memory Hierarchy – Main Memory Main memory is an internal storage area in a computer, which is availed to store data and programs either permanently or temporarily. AOCT004-4-1 CSA Memory Organisation SLIDE 13  Memory Hierarchy – Main Memory Main memory is a critical component of all computing systems : server, mobile, embedded, desktop and sensor Main memory system must scale (in size technology, efficiency, cost and management algorithms) to maintain performance growth and technology scaling benefits. AOCT004-4-1 CSA Memory Organisation SLIDE 14  Memory Hierarchy – Main Memory Primary storage (or main memory or internal memory), often referred to simply as memory, is the only one directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required. Main memory is directly or indirectly connected to the CPU via a memory bus. It is actually two buses (not on the diagram): an address bus and a data bus. The CPU firstly sends a number through an address bus, a number called memory address, that indicates the desired location of data. Then it reads or writes the data itself using the data bus. It is divided into RAM and ROM. AOCT004-4-1 CSA Memory Organisation SLIDE 15  Memory Hierarchy – Secondary Storage The computer usually uses its input/output channels to access secondary storage and transfers the desired data using intermediate area in primary storage. Secondary storage does not lose the data when the device is powered down—it is non-volatile. Per unit, it is typically also an order of magnitude less expensive than primary storage. The secondary storage is often formatted according to a file system format, which provides the abstraction necessary to organize data into files and directories, providing also additional information (called metadata). Hard disk are usually used as secondary storage. AOCT004-4-1 CSA Memory Organisation SLIDE 16  LEARNING OUTCOME 2 TYPES OF SEMICONDUCTOR MEMORY (RAM,ROM) Discuss different types of semiconductor memory AOCT004-4-1 CSA Memory Organisation SLIDE 17  Random Access Memory (RAM) The RAM family includes two important memory devices: static RAM (SRAM) dynamic RAM (DRAM) The primary difference between them is the lifetime of the data they store. SRAM retains its contents as long as electrical power is applied to the chip. If the power is turned off or lost temporarily, its contents will be lost forever. DRAM, on the other hand, has an extremely short data lifetime- typically about four milliseconds. This is true even when power is applied constantly. DRAM controller is used to refresh the data before it expires, the contents of memory can be kept alive for as long as they are needed. So DRAM is as useful as SRAM after all. AOCT004-4-1 CSA Memory Organisation SLIDE 18  Random Access Memory (RAM) (cont.)  Double Data Rate synchronous dynamic random access memory or also known as DDR1 SDRAM is a class of memory integrated circuits used in computers.  The interface uses double pumping (transferring data on both the rising and falling edges of the clock signal) to lower the clock frequency.  One advantage of keeping the clock frequency down is that it reduces the signal integrity requirements on the circuit board connecting the memory to the controller. AOCT004-4-1 CSA Memory Organisation SLIDE 19  Random Access Memory (RAM) (cont.)  DDR2 memory is fundamentally similar to DDR SDRAM. Still, while DDR SDRAM can transfer data across the bus two times per clock, DDR2 SDRAM can perform four transfers per clock. DDR2 uses the same memory cells, but doubles the bandwidth by using the multiplexing technique.  The DDR2 memory cell is still clocked at the same frequency as DDR SDRAM and SDRAM cells, but the frequency of the input/output buffers is higher with DDR2 SDRAM. The bus that connects the memory cells with the buffers is twice wider compared to DDR.  Thus, the I/O buffers perform multiplexing: the data is coming in from the memory cells along a wide bus and is going out of the buffers on a bus of the same width as in DDR SDRAM, but of a twice bigger frequency. This allows to increase the memory bandwidth without increasing the operational frequency. AOCT004-4-1 CSA Memory Organisation SLIDE 20  Random Access Memory (RAM) (cont.) AOCT004-4-1 CSA Memory Organisation SLIDE 21  Random Access Memory (RAM) (cont.) AOCT004-4-1 CSA Memory Organisation SLIDE 22  Read Only Memory (ROM)  ROM is a class of storage medium used in computers and other electronic devices.  Data stored in ROM cannot be modified.  A program for a ROM or PROM is simply a multiple-output truth table.  ROM holds programs and data permanently when computer is switched off.  Data can be read by the CPU in any order ROM is also direct access.  The contents of ROM is fixed at the time of manufacture.  Stores a program called the bootstrap loader that helps starts up the computer.  Access time of between 10 to 50 nana seconds. AOCT004-4-1 CSA Memory Organisation SLIDE 23  Read Only Memory (ROM) (cont.)  Types of ROM 1. PROM (Programmable Read Only Memory)  Empty of data when manufactured  May be permanently programmed by the user. 2. Erasable Programmable Read Only Memory (EPROM)  Can be programmed, erased and reprogrammed.  The EPROM chip has a small window on top allowing it to be erased by shining ultra-violet light on it.  After reprogramming the window is covered to prevent new contents being erased.  Access time is around 45-90 nanoseconds AOCT004-4-1 CSA Memory Organisation SLIDE 24  Read Only Memory (ROM) (cont.) 3. EEPROM (Electrically Erasable Programmable Read Only Memory)  Reprogrammed electrically without using Ultraviolet light  Must be removed from the computer and placed in a special machine to do this.  Access between 45 to 200 nano seconds. 4. Flash ROM  Similar to EEPROM  However, can be reprogrammed while still in the computer.  Easier to upgrade programs stored in Flash ROM.  Used to store programs in devices.  Example: Array of memory cells AOCT004-4-1 CSA Memory Organisation SLIDE 25  Secondary Storage  Anything outside of “primary memory”.  Storage that does not permit direct instruction execution or data fetch by load/store instructions.  It’s large, cheap, non-volatile and slow. AOCT004-4-1 CSA Memory Organisation SLIDE 26  Secondary Storage (cont.)  anything outside of “primary memory”  storage that does not permit direct instruction execution or data AOCT004-4-1 CSA Memory Organisation SLIDE 27  Secondary Storage (cont.) Files can be allocated on disk in different ways, e.g.:  1. contiguous allocation like memory fast and simplifies directory access inflexible, causes fragmentation, needs compaction 2. linked structure each block points to next block, directory points to first good for sequential access (bad otherwise) 3. indexed structure an “index block” contains pointers to many other blocks better for random access may need multiple index blocks (linked together) AOCT004-4-1 CSA Memory Organisation SLIDE 28  Secondary Storage (cont.) AOCT004-4-1 CSA Memory Organisation SLIDE 29  Characteristics of Computer Storage Devices Storage technologies at all levels of the storage hierarchy can be differentiated by evaluating certain core characteristics. These core characteristics are,  Volatility: Whether the stored data will remain or not when the power supply is disconnected.  Differentiation: Whether it’s a Dynamic random access memory or static memory.  Accessibility: Whether it’s Random-access or Sequential access  Addressability: Whether it’s a Location-addressable, File addressable, or Content-addressable.  Mutability: Whether it’s a Read/write storage or mutable storage, Read-only storage, or a Slow write, fast read storage. AOCT004-4-1 CSA Memory Organisation SLIDE 30  Types of Computer Storage Devices There are four types of computer storage devices, 1. Magnetic Storage devices 2. Optical Storage devices 3. Flash Memory devices 4. Online Cloud Storage devices AOCT004-4-1 CSA Memory Organisation SLIDE 31  LEARNING OUTCOME 3 MEMORY CAPACITY Calculate memory capacity of a given scenario AOCT004-4-1 CSA Memory Organisation SLIDE 32  Memory Capacity * bit = smallest unit of computer memory * nibble = 4 bits * byte = 8 bits * kilobyte = 1024 byte = 1 kb * megabyte = 1024 kb = 1 mb * gigabyte = 1024 mb = 1 gb * terabyte = 1024 gb = 1 tb * petabyte = 1024 tb = 1pb AOCT004-4-1 CSA Memory Organisation SLIDE 33  Watch This!~ https://www.youtube.com/watch? v=PujjqfUhtNo&list=PLBlnK6fEyqRjdT1xkkBZSXKwFKqQoYhwy AOCT004-4-1 CSA Memory Organisation SLIDE 34  LEARNING OUTCOME 4 MEMORY ORGANISATION Explain memory organisation and relate it with CPU instruction processing cycle AOCT004-4-1 CSA Memory Organisation SLIDE 35  The Operation of Memory Main memory consist of cells, each of which can hold a single value and each of which has a single address. The MAR & MDR acts as an interface between the CPU & memory. – MDR is also called memory buffer register. The MAR holds the address to be “opened”. The MAR is connected to a decoder that interprets the address and activates a single address line into the memory. AOCT004-4-1 CSA Memory Organisation SLIDE 36  Summary of Main Teaching Points Some fundamental and enduring properties of hardware and software: – Fast storage technologies cost more per byte and have less capacity. – The gap between CPU and main memory speed is widening. – Well-written programs tend to exhibit good locality. These fundamental properties suggest an approach for organizing memory and storage systems known as a memory hierarchy. Memory Organisation – The operation of memory is intimately related to two registers in particular, the memory address register and memory data register AOCT004-4-1 CSA Memory Organisation SLIDE 37 AOCT004-4-1 CSA Memory Organisation SLIDE 38  See you in the next lecture! THANK YOU AOCT004-4-1 CSA Memory Organisation SLIDE 39