RAM - created from Mind Map

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Type

Memory Upgrade Considerations

Parity vs Non-Parity

ECC vs non-ECC Memory

RAM Configurations

Single-Sided vs Double-Sided

RAM Compatibility

Installing Memory

SRAM Static random-access memory (SRAM)

SDRAM Synchronous DRAM (SDRAM)

DDR SDRAM

DDR2 SDRAM Double data rate 2 SDRAM (DDR2 SDRAM)

DDR3 SDRAM Double data rate 3 SDRAM (DDR3 SDRAM)

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

both methods depend upon the presence of an additional memory chip over the chips required for the data bus of the module. For example, a module that uses eight chips for data would use a ninth chip to support parity or ECC. If the module uses 16 chips for data (two banks of eight), it would use the 17th and 18th chips for parity

ECC is recommended for maximum data safety, although parity and ECC do provide a small slowdown in performance in return for the extra safety. ECC memory modules use the same types of memory chips used by standard modules, but they use more chips and might have a different internal design to allow ECC operation. ECC modules, like parity-checked modules, have an extra bit for each group of eight data bits.

Single-Channel

Dual-Channel

Triple-Channel

Quad-Channel

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. Many, but not all, of these modules use both sides of the module for memory. However, the use of smaller memory chips enables “double-sided” modules to have all of the chips on one side.

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

Surprisingly, the CompTIA A+ 220-901 exam lists installing memory in laptops as an objective (220-901 objective 3.1), but it does not list installing memory in desktop computers. Nevertheless, this is an important skill to learn and understand.