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RAM

RAM. Chapter 7. Overview. In this Lecture, you will learn how to Identify the different types of DRAM packaging Explain the varieties of RAM Select and install RAM Perform basic RAM troubleshooting. Program Execution.

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RAM

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  1. RAM Chapter 7

  2. Overview In this Lecture, you will learn how to Identify the different types of DRAM packaging Explain the varieties of RAM Select and install RAM Perform basic RAM troubleshooting

  3. Program Execution Program code is copied from your hard drive into RAM before it is executed Figure 1: Mass storage holds programs, but programs need to run in RAM.

  4. Organizing DRAM(continued) CPU accesses memory via MCC Figure 3: The MCC accessing data on RAM soldered onto the motherboard

  5. Consumer RAM Even though RAM comes in packages wider than bytes, RAM is still described in bytes, such as a 1-GB stick or a 2-GB stick

  6. Types of RAM

  7. Requires all RIMM slots (in a pair) to be populated • Continuity RIMM (CRIMM) sticks were essentially RIMM terminators. • RDRAM was proprietary and licensed to work only with Intel systems for several years. • The goal was to push AMD out of the marketplace, but the result was growth of other types of memory and memory chips. RDRAM (continued) RDRAM CRIMM

  8. Fast RAM supported by AMD and other manufacturers • Doubles the throughput over SDRAM (makes two processes for each clock cycle) • Commonly referred to as DDR, DDR RAM, and DDRAM • Comes in 184-pin DIMMs • Slots are keyed with guide notches, so you cannot insert RAM in incorrect slots DDR SDRAM DDR SDRAM 172-pin DDR SDRAM micro-DIMM

  9. Base clock is 100 MHz to 300 MHz with the DDR speed rating double the clock speed • To determine the PC speed rating (bytes per second), multiply the DDR speed, in MHz, by 8 • For example, a chip with a clock speed of 200 and doubled DDR speed rating of 400 would be referred to as a PC 3200 (400 MHz × 8) • Supported as standard system RAM, even by Intel for the Pentium 4 DDR SDRAM (continued)

  10. Can make use of dual-channel architecture • Similar to Rambus in how it improves performance • Works only when two slots are populated • Dual slots are often blue • If third slot exists, it is black DDR SDRAM (continued)

  11. DDR2 Figure 16: 240-pin DDR2 DIMM Doubled the clock to increase buffering and overall performance Uses 240-pin DIMM (not compatible with DDR DIMM)

  12. DDR2 (continued) DDR2 Speeds • PC rating is determined similar to how DDR is determined (with another doubling), and prefixed by a 2 • For example, for DDR2 with a clock speed of 200 MHz, the DDR I/O speed would be 400 MHz, the DDR2 speed rating would be DDR2-800, and the PC speed rating would be PC2-6400

  13. Quadruples the clock to increase buffering and overall performance • Uses 240-pin DIMM (not compatible with DDR2) • PC rating is determined similar to how DDR2 is determined (with another doubling), and prefixed by a 3 • For example, for DDR3 with a clock speed of 200 MHz, the DDR I/O speed would be 800 MHz, the DDR3 speed rating would be DDR3-1600, and the PC speed rating would be PC3-12800 DDR3 DDR3 Speeds

  14. Some chipsets that support DDR3 also support a feature called triple-channel memory • Works a lot like dual-channel before it, but with three sticks of RAM instead of two • Intel’s LGA 1366 platform supports triple-channel memory • No AMD processors support a triple-channel feature. DDR3 (continued) Figure 17: DDR2 DIMM on top of a DDR3 DIMM

  15. Double-sided DIMMs • Many sticks come in single-sided versions and double-sided versions. Some double-sided sticks can’t go into all motherboards. • Latency: Refers to how quickly the RAM responds to the electrical signal • High latency: High wait time. Takes longer for RAM to respond. CL3 is high latency. • Lower latency: Lower wait time. RAM can get the signal out in fewer clock ticks. CL2 is low latency. • The goal is to match the RAM with the motherboard. If necessary, when swapping RAM, the RAM timings can be adjusted in BIOS. RAM Variations

  16. RAM Variations (continued) Figure 18: Double-sided DDR SDRAM Figure 19: Why is one more expensive than the other?

  17. Parity and ECC: Detect errors in memory • Parity allows the computer to detect whether an error occurred in the reading or writing of data in memory. • Error correction code (ECC) is an improvement over parity. Not only can errors be detected, but they can also be corrected. • ECC is slower because of the extra calculations required. • Parity and ECC are used only on higher-end workstations and servers. Often applications will check and/or correct errors on the fly instead of depending on the hardware to do so. RAM Variations (continued)

  18. Working with RAM What's wrong with this picture? Figure 21: Don't do this! Grabbing the contacts is a bad idea!

  19. Adding more RAM almost always improves overall system performance, processing speed, and stability. • Determine whether insufficient RAM is the cause of system problems. • Pick the proper RAM for the system. • Use good installation practices such as keeping RAM sticks in antistatic packaging and following strict ESD practices. Why Add More RAM?

  20. Two symptoms show the need for more RAM: • General system sluggishness • Disk thrashing or excess hard drive accessing, generally indicated by using excessive movement of files between RAM and a swap file or virtual memory space on hard drive Why Add More RAM? (continued)

  21. Is your system sluggish? • A slow-running system, especially with more programs running, indicates RAM may be a bottleneck. • Are you experiencing disk thrashing? • Disk thrashing occurs when data is swapped between physical RAM and virtual RAM (the paging file). The symptom of disk thrashing is that the disk drive LED is blinking feverously and you can hear it almost constantly moving. Do You Need More RAM?

  22. Page File: Windows uses a portion of the hard drive as an extension of system RAM—called a RAM cache • A RAM cache is a block of cylinders on a hard drive set aside as what's called a page file, swap file, or virtual memory. • When the PC starts running out of real RAM because you've loaded too many programs, the system swaps programs from RAM to the page file, opening more space for programs currently active. • All versions of Windows use a page file. Do You Need More RAM? (continued)

  23. Determining current RAM capacity • Use Properties for My Computer/Computer to see the RAM configuration. Do You Need More RAM? (continued)

  24. Do You Need More RAM? (continued) Figure 30: Mike has a lot of RAM!

  25. Do You Need More RAM? (continued) Figure 31: Performance tab in Windows XP7 Task Manager

  26. The RAM sticks are keyed so that they can go in only one way. • Line up the keys and place the stick in the slot. • Push down and the tabs will lock into position. • SPD (Serial Presence Detect). Upon power-up, the SPD chip detects the memory in the system and reports it to the BIOS. • Any program can query the SPD. CPU-Z, a Cool Tool, displays some of the SPD information. Installing DIMMs and RIMMs

  27. Figure 34: Inserting a DIMM Installing DIMMs and RIMMs (continued) Figure 35: SPD chip on a stick

  28. Figure 37: Hey, where’s the rest of my RAM?! Installing DIMMs and RIMMs (continued) Figure 38: RAM count after proper insertion of DIMMs

  29. For years, laptops had proprietary RAM packages, making this difficult. • However, the acceptance of SO-DIMMs over the years has made it much easie.r • First, power off, unplug, and remove the battery pack—follow ESD procedures. • Identify the access point for the SO-DIMM. • This is usually either under the keyboard or via an access panel on the back. • Replace the SO-DIMM. Installing SO-DIMMS on Laptops

  30. Figure 39: A RAM access panel on a laptop Installing SO-DIMMS on Laptops (continued) Figure 40: Snapping in an SO-DIMM

  31. Troubleshooting RAM

  32. Memory errors can include: • Parity errors • ECC error messages • System lockups • Page faults • Other error screens in Windows Memory Errors

  33. Write down memory error addresses. • If the error returns with the same address each time, it is likely a RAM stick failure. • If the error address changes, it is likely not a RAM failure. • System lockups and page faults often indicate RAM problem. • RAM and parity errors can trigger a non-maskable interrupt (NMI) that results in the Blue Screen of Death (BSoD). Memory Errors (continued)

  34. Memory Errors (continued) Figure 41: Windows error message

  35. Memory Errors (continued) Figure 42: Blue Screen of Death

  36. Not all intermittent errors are caused by bad RAM • Dying power supply, electrical interference, and buggy applications or hardware can also produce intermittent errors. Memory Errors (continued)

  37. Several RAM testing devices are available, but many are expensive. • Can replace one stick at a time until problems disappear. • Use a software-based tester such as Memtest86. • Windows 7 includes the Memory Diagnostics Tool, which can automatically scan your computer’s RAM when you encounter a problem. Testing RAM

  38. Testing RAM (continued) Figure 43: Memtest86 in action

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