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Lesson 3-RAM

Lesson 3-RAM. Overview. Introduction to Random Access Memory (RAM). Types of RAM technologies. RAM packages. Adding and upgrading RAM. Introduction to RAM. The CPU uses RAM to store active programs and data temporarily.

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Lesson 3-RAM

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  1. Lesson 3-RAM

  2. Overview • Introduction to Random Access Memory (RAM). • Types of RAM technologies. • RAM packages. • Adding and upgrading RAM.

  3. Introduction to RAM • The CPU uses RAM to store active programs and data temporarily. • Programs stored on the hard drive need to be loaded into RAM to enable the CPU to swap data in and out. • The CPU uses the Northbridge for all its communication with RAM. • RAM holds the data only temporarily. It cannot hold anything without electricity.

  4. Introduction to RAM • RAM speed is measured in nanoseconds (ns). • RAM usually consists of sticks, which are small circuit boards having several small chips mounted on the surface. • The chips mounted on RAM sticks work together to form millions of rows of 64-bit 8-wide RAM. • The CPU sends requests for data stored in RAM to the Northbridge chip via the address bus.

  5. Introduction to RAM • The CPU turns current to the wires of the address bus on and off in certain patterns to represent specific memory addresses. • Wires that have a charge applied represent the value 1 while non-charged wires represent 0. • The Northbridge chip retrieves the data from RAM and drops it onto the external data bus for pickup by the CPU.

  6. Types of RAM Technologies • Fast Page Mode (FPM) RAM. • Extended Data Output (EDO) RAM. • Synchronous Dynamic Random Access Memory (SDRAM). • Double Data Rate SDRAM (DDR SDRAM). • Rambus Dynamic Random Access Memory (RDRAM).

  7. The Fast Page Mode (FPM) RAM • FPM RAM allowed the Northbridge fast access to each bit of data, but required at least two clicks of the system clock to do so. • FPM was relatively inexpensive and fast and was thus used extensively until replaced by even faster technologies.

  8. Extended Data Output (EDO) RAM • The Northbridge used two wires called the row array strobe (RAS) and column array strobe (CAS) to access information stored in a row of RAM. • EDO RAM eliminated the need to relight the RAS wire for each column.

  9. Extended Data Output (EDO) RAM • FPM and EDO RAM were both asynchronous, meaning they did not have a clock chip. • FPM RAM used speeds in the 200 ns range and EDO RAM got as fast as 50 ns.

  10. Synchronous Dynamic Random-Access Memory (SDRAM) • SDRAM included a clock, which enabled the Northbridge to predict the number of clock cycles needed for RAM to produce the requested data. • SDRAM speed is measured in hertz (Hz), reflecting the cycles per second of the clock. • SDRAM speeds are typically matched to the motherboard speed.

  11. Double Data Rate SDRAM (DDR SDRAM) • DDR SDRAM is SDRAM that has the ability to make two RAM accesses during a single clock cycle. • DDR SDRAM is most commonly available in 200, 266, 333, and 400 MHz speeds.

  12. Rambus Dynamic Random-Access Memory (RDRAM) • RDRAM is a very high-speed type of clocked RAM that runs at 400 or 533 MHz. • RDRAM is more expensive than DDR SDRAM, so it tends to show up only in high-end systems.

  13. RAM Packages • RAM packages are physical form factors required for installing and configuring the RAM. • Selecting the right package involves identifying the motherboard and the processor that it will be used on.

  14. RAM Packages • Single Inline Memory Modules (SIMMs). • Dual Inline Memory Modules (DIMMs). • Small Outline (SO) DIMMs. • RIMMs.

  15. Single Inline Memory Modules (SIMMs) • SIMMs were used for both FPM and EDO RAM. • They came in 30-pin or 72-pin modules. • Some motherboards support either pin variety. However, motherboards only support one of the two technologies, FPM or EDO.

  16. Single Inline Memory Modules (SIMMs) • The number of SIMM sticks that must go into the motherboard as a group defines a bank. • A bank that has a SIMM RAM installed is referred to as being populated. • A bank that is empty is termed unpopulated. • Systems that use 72-pin SIMMS only require two modules to make up a bank.

  17. Dual Inline Memory Modules (DIMMs) Common DIMM Implementations Today

  18. Small Outline (SO) DIMMs Common SO DIMM Implementations Today

  19. RIMMs • RIMMs are just the Rambus version of DIMMs. • RIMMs have 184 pins and are notched in such a way that they cannot be accidentally placed in a DIMM socket. • RIMMs usually are installed in pairs.

  20. RIMMs • Rambus specifies special bank fillers called Continuity RIMMs (CRIMMs) that must be placed in all unused banks on the motherboard. • The speeds of RDRAM are PC600, PC700, PC800, and PC1066. • RDRAM also addresses the needs of laptops by providing a 160-pin RIMM.

  21. Adding and Upgrading RAM • Reasons for adding RAM. • Upgrading RAM.

  22. Reasons for Adding RAM • Adding or upgrading the RAM can increase both, the system performance as well as stability. • It allows a user to open more programs simultaneously. • Systems with insufficient RAM use a portion of the hard drive as RAM.

  23. Reasons for Adding RAM • The PC automatically begins to swap the less-used programs out of RAM to the hard drive to make room for the most used program. • The area on the hard drive that holds these least-used programs is called the swap file and the entire process is known as using virtual memory.

  24. Reasons for Adding RAM • Excessive swap file accesses and writes create an unusual scratching sound commonly called a hard drive thrash. • Too much hard drive thrashing is another sign that more RAM needs to be added.

  25. Upgrading RAM • Research • Installation • Verification

  26. Research • Determining RAM capacity. • Choosing single- or double-sided sticks. • Assessing the number of available slots. • Determining the speed.

  27. Installation The following components are required to install RAM: • A motherboard with SIMM slots. • SIMM sticks. • An antistatic wrist strap.

  28. Verification If the system does not boot after installing RAM, the installer may have made one of the following mistakes: • The RAM is inserted improperly. • The motherboard requires multiple sticks to fill a bank and some slots in the bank were left open. • The installed RAM is too slow for the system.

  29. Verification If the system does not boot after installing RAM, the installer may have made one of the following mistakes (continued): • The installer forgot to add CRIMMs. • One of the RAM sticks is bad.

  30. Summary • RAM is the workspace where the CPU stores programs that are running. • The CPU directs the Northbridge chip to update and retrieve data. • Five types of RAM technologies are FPM, EDO, SDRAM, DDR SDRAM, and RDRAM. • Two sizes of SIMMs are 30-pin SIMMs and 72-pin SIMMs.

  31. Summary • RDRAM uses a special DIMM called RIMM. The unused slots on the motherboard are filled with a special stick called a CRIMM. • Using too much virtual memory causes the system to slow down. • RAM is counted in true millions of bytes, not megabytes. • RAM is simple and is an easy way to improve the performance of a slow system.

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