CompTIA A+ Certification All-in-One Exam Guide, Exams 220-1001 & 220-1002

by Mike Meyers

DDR4. Make sure you know their individual characteristics and differences. DDR3 DIMMs have 240 pins, for example, and DDR3 SO-DIMMs have 204 pins. DDR3 doubles the buffer of DDR2 from 4 bits to 8 bits, giving it a huge boost in bandwidth over older RAM. Not only that, but some DDR3 (and later) modules also include a feature called XMP, or Extreme Memory Profile, that enables power users to overclock their RAM easily, boosting their already fast memory. DDR3 modules also use higher-density memory chips, up to 16-GB DDR3 modules. AMD’s version of XMP is called AMP, for AMD Memory Profile. NOTE Do not confuse DDRx with GDDRx; the latter is a type of memory used solely in video cards (e.g., GDDR5). See Chapter 17, “Display Technologies,” for the scoop on video-specific types of memory. Some motherboards that support DDR3 also support features called triple-channel architecture or quad-channel architecture, which work a lot like dual-channel, but with three or four sticks of RAM instead of two. More recently, Intel and AMD systems have switched back to dual-channel, although there’s plenty of systems out there using triple- or quad-channel memory. EXAM TIP Be sure you are familiar with single-, dual-, triple-, and quad-channel memory architectures.