RAM Types and Features

RAM Types and Features

1. RAM is used for programs and data as well as by the operating system for disk caching (using RAM to hold recently accessed information)

   • Memory Upgrade Considerations
     • Memory module form factor (240-pin DIMM, 184-pin DIMM, 168-pin DIMM, 204-pin SO-DIMM, and so on)
       • Memory chip type used on the module (SDRAM, DDR SDRAM, and so on)
         • Memory module speed (PC3200, PC2-6400, PC3-12800, and so on)
           • Memory module latency
             • Error checking (parity, non-parity, ECC)
               • Allowable module sizes and combinations
                 • The number of modules needed per bank of memory
                   • Whether the system requires or supports multi-channel memory (two or more identical memory modules accessed together instead of one at a time)
                     • The total number of modules that can be installed
   • SO-DIMM vs DIMM
   • Single-Sided vs Double-Sided
     • A single-sided (more properly known as single-ranked) module has a single 64-bit wide bank of memory chips. A double-sided (double-ranked) module has two 64-bit banks of memory stacked for higher capacity.
   • RAM Compatibility
     • When it comes to memory, compatibility is important. The memory module type must fit the motherboard; speed must be compatible and the module storage size/combination must match your computer system as well. The labels on the memory modules shown in Figure 4-1 list the manufacturer, module type, size, and speed, and most also list the CAS latency (CL) value. If you want to buy additional modules of the same size, you can use this information to purchase additional modules.
   • Installing Memory
     • Step 1. Line up the modules’ connectors with the socket. DIMM modules have connections with different widths, preventing the module from being inserted backwards.
       • Step 2. Verify that the locking tabs on the socket are swiveled to the outside (open) position. Some motherboards use a locking tab on only one side of the socket
         • Step 3. After verifying that the module is lined up correctly with the socket, push the module straight down into the socket until the swivel locks on each end of the socket snap into place at the top corners of the module (see Figure 4-5). A fair amount of force is required to engage the locks. Do not touch the metal-plated connectors on the bottom of the module; this can cause corrosion or ESD
   • RAM Types
     • SRAM (Static random-access memory)
       • SDRAM (Synchronous DRAM)
         • DDR SDRAM
           • DDR2 SDRAM
             • DDR3 SDRAM
   • RAM Configurations
     • Single-Channel
     • Dual-Channel
     • Quad-Channel
     • Triple-Channel

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