Memory Terms and Definitions Chapter Objectives After completing this chapter you will Understand memory related terminology Be able to install and remove memory chips Understand how memory works with different operating systems Be able to optimize memory under different operating systems Be able to troubleshoot memory problems Memory Overview Types of Memory RAM Random Access Memory is volatile memory found on the motherboard and stores the operating system the software applications and the data being used by all of the software ROM Read Only Memory is a non volatile type of memory that keeps data in chips even when the computer is shut off Types of RAM DRAM Dynamic RAM is less expensive but slower than SRAM It requires periodic refreshing of the electrical charges holding the 1s and 0s SRAM Static RAM is faster but more expensive than DRAM It is also known as cache memory or L2 cache Memory Overview Memory Terms Refreshing Periodically rewriting information to the memory chip Nanosecond A billionth of a second Pipelining The process by which microprocessors and memory obtain computer software instructions in a timely fashion Cache Memory also known as SRAM can be found on the motherboard but normally is found inside the CPU Cache memory holds the most frequently used data so the CPU does not return to the slower DRAM chips to obtain the data Memory Physical Packaging Types of Memory Packaging DIP Dual In line Package A chip that has a row of legs running down each side SIMM Single In line Memory Module Available in 30 pin and 72pin configurations DIMM Dual In line Memory Module 168 pin configuration and used in Pentium Pentium Pro Pentium II or Pentium III motherboards DDR DIMM 184 pin configuration and used in AMD Athlon computers Pentium 4 computers and high end servers RIMM Type of memory module used on video adapters and future motherboards Memory Physical Packaging Methods of Error Checking Parity A method for checking the accuracy of data going in or out of the memory chips Non parity Memory chips that do not use any error checking ECC Error Correcting Code Uses a mathematical algorithm to detect up to four bit memory errors and correct one bit memory errors A computer system that uses parity must have parity memory installed Memory Physical Packaging Memory Chips Memory Figure 1 Memory Physical Packaging 184 Pin DDR DIMM and RIMM Memory Figure 2 Memory Chip Capacity Most Common Memory Capacity DIP chips 64Kb 256Kb or 1MB 30 Pin SIMM Modules 256Kb 512Kb 1MB 2MB and 4MB 72 Pin SIMM Modules 4MB 8MB 16MB 32MB 64MB and 128MB DIMM Modules 8MB 16MB 32MB 64MB 128MB 256MB 512MB and 1024MB RIMM Modules 64MB 128MB and 256MB Identifying Chip Capacity and Speed The only way to be certain of the capacity is to install the SIMM in a computer or research the manufacturer s number on the internet Access Time How fast information goes into a memory chip or is removed from the chip The lower the number of nanoseconds the faster the access time of the memory chips Identifying Chip Capacity and Speed Chip Capacity Memory Figure 3 Identifying Chip Capacity and Speed Memory Chip Access Time Memory Figure 4 Memory Chip Technologies Technology to provide faster DRAM speeds FPM Fast Page Mode EDO Extended Data Out BEDO Burst EDO Memory Chip Technologies SDRAM Synchronous DRAM provides very fast burst memory access by placing new memory address on the address bus before prior memory address retrieval and execution completes The PC100 SDRAM DIMMs are designed for the 100MHz front side bus The PC133 SDRAM DIMMs are designed for the 133MHz front side bus but will work with the 100MHz motherboards SPD Serial Presence Detect is an extra EEPROM feature of SDRAM DIMM PC100 and PC133 standard that adjusts the motherboard timings for the best CPU and RAM performance Registered SDRAM or Buffered SDRAM delays all data transfers by one clock to ensure accuracy It is used in network servers and higher end computers Unbuffered SDRAM is the memory type most often used in home computers and in low to medium powered computers VCM Virtual Memory Channel is a memory chip alternative to SDRAM that fits in DIMM slots The motherboard chipset must support it Memory Chip Technologies Other Types of RAM RDRAM Rambus DRAM Developed by Rambus Inc and used in Pentium 4 computers and some video adapters RDRAM is packaged in RIMMs When RIMMs are used all memory slots must be filled Put an C RIMM Continuity RIMM which is a blank RIMM in any empty slot DDR RAM Double Data Rate RAM also called DDR SDRAM Data can be transmitted on both sides of the clock signal rising and falling edges VRAM Video RAM A type of memory found on a video card WRAM Windows RAM Dual ported memory found on video adapters SGRAM Synchronous Graphic Random Access Memory Used on video adapters and graphics accelerators and have special memory techniques that speed up graphics intensive functions Memory Chip Technologies Memory Table 2 Memory Banks Bank or Memory Bank is one or more memory chips that work together to transfer data to and from the CPU and a device External Data Lines or External Data Path is the electronic lines that allow the microprocessor to communicate with external devices Parity Chip is a memory chip on a memory bank that checks for data accuracy Memory Banks 8088 Memory Banks Memory Figure 6 Memory Banks 80386 Memory Banks Memory Figure 7 Buying the Right 72 Pin SIMM Purchasing the correct memory can be difficult Advertisements for memory can often be confusing and even misleading Always refer to your motherboard documentation for the correct type of memory to install with your computer Buying the Right 72 Pin SIMM Sample of 72 Pin SIMM Advertisements Memory Figure 8 Populating Pentium and Higher Motherboards Computers with a Pentium processor and SIMM sockets have two SIMMs that must be installed in one bank for the computer to operate Pentium Pro computers usually have one DIMM socket as a bank and two 72 Pin SIMM sockets for another bank of memory Pentium 4s ship with DIMM or RIMM sockets Populating Pentium and Higher Motherboards Pentium Memory Banks Memory Figure 9 Populating Pentium and Higher Motherboards Pentium Memory Figure 10 Buying the Right DIMM or RIMM Be careful with purchasing DIMMs and always refer to the documentation DIMM Terminology CAS Column Address Strobe Latency is the amount of time that passes before the processor moves on to the next memory address RAS Row Address Strobe is a signal that selects a specific