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Understanding Memory and Memory Devices

Understanding Memory and Memory Devices. Christina Angstadt Karlie Meyer Kait Sharer. Overview. History Intel 1103 Memory Modules Volatile vs. Non-Volatile ECC Memory Single Sided vs. Double Sided Parity vs. Non-Parity What is RAM? Types of RAM Single Channel vs. Dual Channel

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Understanding Memory and Memory Devices

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  1. Understanding Memory and Memory Devices Christina Angstadt Karlie Meyer Kait Sharer

  2. Overview History Intel 1103 Memory Modules Volatile vs. Non-Volatile ECC Memory Single Sided vs. Double Sided Parity vs. Non-Parity What is RAM? Types of RAM Single Channel vs. Dual Channel Memory Speeds Desktop vs. Laptop Memory How much RAM is enough? Memory Recommendations How to Install RAM

  3. History • Punch Cards & Tape (-1970): helped to develop the ‘idea’ of main memory • How to store programs, data & results permanently • The Williams Tube (1948): storage device for Manchester Baby computer • Fired beam of electrons down a vacuum tube, then detected static charges caused by the beam. • Store around 1Kb • Parallel with today’s DRAM chip • Also needed to be refreshed • Magnetic Core (1950 -1970): dominant form of technology • Magnetic ceramic rings called cores • Stored information using polarity of magnetic field • Access speeds between 6msec – 1.2msec

  4. Card from a Fortran program Z(1) = Y + W(1)

  5. Intel 1103 • First Dynamic RAM chip • Developed by Intel (1970) • 1 Kb of DRAM • Entire refresh done in 32 read cycles • Required every 2 ms • Replaced magnetic core technology for main memory • Faster (ns) compared to core (ms) • Best selling semiconductor memory chip by 1972 • High data capacity & Low cost • (1 cent / bit) • Allowed for first mass-produced home computers (PC’s)

  6. SIMM (Single Inline Memory Module) 8MB RAM 30 or 72 Connector contacts DIMM (Dual Inline Memory Module) 64MB RAM 168 Connector contacts (pins) Two pairs of SIMMs on a single board Memory Modules • Circuit Board that holds memory chips • Connects to motherboard

  7. Data is lost when powered down Form of primary storage Directly accessible to CPU RAM (Random-Access Memory) Faster to read from/write to Needs to be periodically refreshed DRAM Retains stored data even when not powered Used for long-term (secondary) storage ROM(Read-Only Memory) Data cannot be modified Fast & expensive Flash Memory Magnetic storage devices Hard disk drive Cheaper but slower Volatile vs. Non-Volatile

  8. ECC Memory • Error-Correcting Code Memory • Introduced by HP in 1993 • Detects and corrects some memory errors • Different from parity (only detects) • RAM was not as stable as it is today • Irregularities could cause data in memory to corrupt • System crash • Hard disk data damage • An additional bit is appended to each byte of RAM • Verifies the validity of each byte • Slow system to about 2% • More expensive • Recommended for servers • Unnecessary otherwise, due to low error rate in today’s memory

  9. ECC Memory 1 58 0 40

  10. 8 memory chips on one side (or 4 on each side) All of the chip’s memory can be seen at the same time Both sides Denser memory modules Larger capacity chips 32M Lower latency times (delay) 16 memory chips (8 on each side) Only one side can be seen by the computer at a time Chip capacity of 16M Slightly slower Single Sided vs. Double Sided

  11. Parity vs. Non-Parity • What is Parity Memory? • Parity memory includes one extra bit of storage for every 8 bits of data • Advantages • Data Integrity • Easier Troubleshooting • Advanced Warning of Hardware Failure • Parity memory usually works in a Non-parity system • Disadvantages • Greater Expense • Harder to Find • Occasional False Positives • Poor Error Handling • Performance Penalty for ECC • What is Non-Parity Memory? • “Regular” memory, One bit of storage for each bit of data • Advantages • Cheaper • Easier to Find b/c more is produced • Little faster than ECC • Disadvantages • Non-parity memory will not work in a parity system

  12. What is RAM? • Volatile • Temporary Storage • “Random Access Memory” : Can access any memory cell directly • Many Types: • DRAM • SRAM • SDRAM • DDR/DDR2/DDR3 • RAMBUS

  13. Types of RAM • DRAM= “Dynamic RAM” • Most Common Form of Memory • 1 Transistor and 1 Capacitor Paired • Create Memory Cell = Bit • Bit holds 0 or 1 • Transistor is a switch • Capacitor = Bucket • Store “1” fills with electrons • Store “0” bucket emptied • Bucket has a leak • Recharge Capacitors holding a 1 • Refresh Operation: • CPU or Memory Controller Reads & Writes Back • 1000s of times per second • DRAM has to be dynamically refreshed • Takes time and slows down memory

  14. Types of RAM cont. • DRAM cont. • Forms the larger system RAM space • Advantages • Structural simplicity • One transistor • One Capacitor • Reaches Very high Density • Cheaper than SRAM • Disadvantages • Slower than SRAM • Has to constantly be reminded what is being stored

  15. Types of RAM cont. • SRAM = “Static RAM” • Flip-flop holds each bit • 4 or 6 transistors & some wiring • Never has to be refreshed • Creates the CPU’s speed-sensitive cache • 3 different states • Standby: Idle • Reading: Data Requested • Writing: Updating Contents

  16. Types of RAM cont. • SRAM cont. • Used where bandwidth or lower power are principle considerations • Advantages • Significantly faster than DRAM • Less power hungry (Especially Idle) • Easier to control • Disadvantages • Takes up more space • Less memory per chip • More expensive • Complex Internal Structure (less dense)

  17. Types of RAM cont. • SDRAM = “Synchronous Dynamic RAM” • Started in 1993 • Typical DRAM is asynchronous : responds as quickly as possible to changes in control inputs • SDRAM is synchronous • Waits for a clock signal before responding to control inputs • Synchronized with the computer’s bus system

  18. Types of RAM cont. • SDRAM cont. • Chip has a more complex pattern of operation than asynchronous DRAM • Widely used in computers • Ability to interleave operations to multiple banks of memory, increasing effective bandwidth • Single Data Rate: Only one word of data transmitted per clock cycle • Supply Voltage 3.3V

  19. DDR/DDR2/DDR3

  20. Types of RAM cont. • DDR SDRAM = “Double Data Rate SDRAM” • Reads/Writes 2 words of data per clock cycle • Supply Voltage reduced to 2.5V • Doubles the minimum read or write unit • DDR2 SDRAM “Double Data Rate 2 SDRAM” • Doubles the minimum read or write again to 4 consecutive words • Simplified to allow higher performance operation • Allows bus rate of the SDRAM to be doubled w/o increasing clock rate of internal RAM operations

  21. Types of RAM cont. • DDR3 SDRAM: “Double Data Rate 3 SDRAM” • 1.5V • Doubles the minimum read or write unit to 8 consecutive words • Doubling of bandwidth and external bus rate w/o having to change the clock rate of internal operations, just the width • With every doubling comes increased latency • DDR4 SDRAM: “Double Data Rate 4 SDRAM” • Release in 2012 • Proposed to run at 1.2V or less • 2 billion data transfers per second

  22. Types of RAM cont. • Rambus DRAM • Types of synchronous dynamic RAM designed by the Rambus Corporation • Data transferred on both rising and falling edges of the clock signal (DDR) • Shows a slight increase in latency, heat output, manufacturing complexity, and cost • Uses a Rambus in-line Memory Module (RIMM) • Operates at higher speeds than normal DRAM • Fitted with a heat spreader to help dissipate the excess heat

  23. Single Channel vs. Dual Channel Memory • Single Channel Memory • Memory bus of 64 bits • Dual Channel Memory • doubles data throughput from the memory to the memory controller • Utilizes two 64-bit data channels, resulting in a 128-bit data path

  24. Dual Channel Memory • Requires a dual-channel-capable motherboard and two or more DDR, DDR2 SDRAM, or DDR3 SDRAM memory modules • Separate channels allow each memory module access to the memory controller, increasing throughput bandwidth • Requires two memory modules plugged into the appointed DIMM slots in order to enable 2 Channel DDR. • Dual-channel technology was created to address the issue of bottlenecks • Under the single-channel architecture, any CPU with a bus speed greater than the memory speed would be susceptible to this bottleneck effect • Dual-channel configuration solves this problem by doubling the amount of available memory bandwidth. Instead of a single memory channel, a second parallel channel is added. With two channels working simultaneously, the bottleneck is reduced.

  25. Memory Speeds • PC100 • PC133 • PC2700 • PC3200 • DDR2-667 • DDR3-1600

  26. PC100 • Synchronous DRAM • operating at a clock frequency of 100 MHz • 64-bit bus • voltage of 3.3 V • PC100 is a standard for internal removable computer random access memory

  27. PC133 • Synchronous DRAM • operating at a clock frequency of 133 MHz • 64-bit-wide bus • voltage of 3.3 V • PC133 was the fastest and final SDRAM standard ever approved by the JEDEC, and delivers a bandwidth of 1064 MB per second • Backward compatible with PC100

  28. PC2700 • Double Data Rate(DDR)-Synchronous DRAM • transfers data on both the rising and falling edges of the clock signal (double pumping) to lower the clock frequency • operating at a clock frequency of 166 MHz • Data transfer rate: 333MHz • Peak transfer rate is 2700 MB/s

  29. PC3200 • Double Data Rate(DDR)-Synchronous DRAM; same concept as PC2700 except: • operating at a clock frequency of 200 MHz • Data transfer rate: 400MHz • Peak transfer rate is 3200 MB/s

  30. DDR2-667 • DDR2 SDRAM is a double data rate synchronous dynamic random access memory interface • Supersedes the original DDR SDRAM • Not compatible with DDRM SDRAM • Double pumping the data bus as in DDR • DDR2 allows higher bus speed • Key difference between DDR and DDR2: • Requires lower power by running the internal clock at one quarter the speed of the data bus • Memory clock: 166 MHz • Peak transfer rate: 5333 MB/s

  31. DDR3-1600 • DDR3 SDRAM or double data rate three synchronous dynamic random access memory • random access memory interface technology used for high bandwidth storage • Ability to transfer at twice the data rate of DDR2 • Memory clock: 200 MHz • Data Rate: 1600 MT/s • Peak Transfer Rate: 12800 MB/s • Not compatible with DDR2

  32. Desktop vs. Laptop Memory • Desktop • DIMMS (Dual In-Line Memory Module) • SDRAM • DDR SDRAM • DDR2 SDRAM • DDR3 SDRAM • Laptop • SO DIMM (Small Outline DIMM) • Smaller version of DIMM modules used in desktops

  33. Laptop Memory • Form factors of laptop memory differ from that of desktop memory including: • Physical size • Pin configuration • Full size DIMM: • 100, 168, 184, or 240 pins • 4.5 to 5 inches in length • SO DIMM • 72, 100, 144, or 200 pins • 2.5 to 3 inches in length

  34. How Much RAM is Enough? • Depends on the O.S. • Windows 98: Operating System and the programs that run on it are less complex • 512 MB – 2GB • Windows XP Professional • 512MB – 4GB • Windows 7 (32-bit) • 1GB – 4GB • Mac OS X • 512MB – 4GB • Linux • 64MB

  35. How Much RAM is Enough? • Depends on computer’s functions • Casual User: Internet browsing, e-mail, music • 512MB – 1GB • Frequent User: Internet browsing, e-mail, word processing, simple graphics programs and games, music & videos, multitasking • 1GB – 2GB • Power User/Student: Internet browsing, e-mail, word processing, photo & video editing, graphics programs & gaming, intensive multitasking • 2GB – 4GB • Professional User: High performance gaming, multimedia editing, high-def video, graphics design & 3D modeling, intensive multitasking • 4GB – 8GB • More memory allows you to run more programs at once, and make them easier to use.

  36. Memory Recommendations Design Software: Gaming Software:

  37. How to Install RAM • What you need to know: • How much RAM you have • C:\> MEM • How much RAM you wish to add • Usually sold in multiples of 16MB • Form factor • Card type (DIMM / RIMM) • RAM type • Some computers require specific types of RAM to operate • Should match existing RAM in type, speed and parity for optimal performance • Most common type is SDRAM • Warranty • Where it goes Installing RAM in a DesktopInstalling RAM in a Laptop

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