Motherboards and Buses - Upgrading and Repairing PCs - page 273

ForperformanceinformationabouttheperformanceofolderbustypessuchasISA,EISA,
VL-BUS, and MCA, see Table 4.71 in Chapter 4 , “ Motherboards and Buses ,” in Upgrad-
ing and Repairing PCs, 19 th edition , available in its entirety on the DVD packaged with
this topic.
Notethatmanyofthebusesusemultiple datacycles (transfers) perclockcycle toachieve
greater performance. Therefore, the data transfer rate is higher than it would seem for a
given clock rate, which allows for an easy way to take an existing bus and make it go
faster in a backward-compatible way.
The Processor Bus (FSB)
The processor bus (also called the FSB) is the communication pathway between the CPU
andmotherboardchipset—morespecificallytheNorthBridgeorMemoryControllerHub.
Over time, the FSB has run at faster speeds to support faster processor, memory and
motherboard speeds. But as the previous table indicates, there are many other buses run-
ning at different speeds in typical systems. The Socket 7 architecture used by Intel's Pen-
tium processors in the mid-1990s, the Socket 478 architecture used by Intel processors in
the early 21 st century, and the Socket 939 architecture used by AMD processors in the
middleofthelastdecaderepresentsignificantmilestonesinprocessorbusdesigns.Socket
939's pioneering use of an integrated memory controller in the processor is now followed
by both AMD and Intel processors.
For an in-depth comparison of the processor and other buses found in systems on Socket
7 (Intel and AMD), Socket 478 (Intel), and Socket 939 (AMD) processors, see “The Pro-