Building or Upgrading Systems - Upgrading and Repairing PCs - page 1180

facturerand,usingaprogramitsupplies,easilyupdatethecodeinyourBIOS.Beforepur-
chasing a motherboard, check to see whether the motherboard is well supported and that
the manufacturer offers downloadable BIOS updates. If you can't easily find BIOS up-
dates, drivers, and documentation for the board on the manufacturer's website, you might
want to choose a board from a different manufacturer that provides better support.
See “ Upgrading the BIOS ,” p. 265 ( Chapter 5 , “ BIOS ”).
You also need to verify that the motherboard and BIOS support both the processor you
plantoinstallinitially andtheprocessoryoumightupgradetointhefuture.Ifthemother-
board and chipset can handle a new processor but the BIOS cannot, a BIOS upgrade may
be available to provide proper support.
In the next few years, the traditional BIOS will be replaced by the Unified Extensible
FirmwareInterface(UEFI),whichenablesbootingfrom3TBharddisksandotherfeatures
not possible with the traditional BIOS.
See “ Unified Extensible Firmware Interface (UEFI) ,” p. 280 ( Chapter 5 ) .
Memory
Main memory typically is installed in the form of dual inline memory modules (DIMMs).
Three physical types of main memory modules are commonly used in PC systems today,
with several variations of each. The main types are as follows:
• 184-pin DDR DIMMs
• 240-pin DDR2 DIMMs
• 240-pin DDR3 DIMMs
Double data rate (DDR) SDRAM memory is an updated variation on SDRAM in which
data is transferred twice as quickly. DDR2 is an improved version of DDR that supports
higher clock speeds and lower voltages. DDR3 is the latest type of main memory on the
market and is the most popular in new systems.
See “ DDR SDRAM ,” p. 328 ( Chapter 6 , “ Memory ” ).
Current motherboards use memory in single-, dual-, or tri-channel modes. In single-chan-
nel mode, each 64-bit wide DIMM is accessed individually, whereas in dual- or tri-chan-
nel mode, the modules are accessed in multiples of 2 or 3 for higher performance. If you
want to take advantage of the faster multichannel modes, make sure you purchase and in-
stall memory modules in matched multiples.
Some memory modules are available with an extra error check bit for each 8 bits. These
are called ECC (error-correcting code) modules. ECC support is normally found only in
server-type processors and motherboards and is rarely found in standard PCs. If you want