A modern motherboard has several components built in, including various sockets, slots, connectors, chips, and so on. Most modern motherboards have at least the following major components on them:

• Processor socket/slot

• Chipset (North/South Bridge or memory and I/O controller hubs)

• Super I/O chip

• ROM BIOS (Flash ROM/firmware hub)

• SIMM/DIMM/RIMM (RAM memory) sockets

• ISA/PCI/AGP bus slots

• CPU voltage regulator

• Battery

Some motherboards also include integrated video, audio, networking, SCSI, Audio Modem Riser (AMR), Communications and Networking Riser (CNR) connectors, or other optional interfaces, depending on the individual board.

Processor Sockets/Slots

The CPU is installed in either a socket or a slot, depending on the type of chip. Starting with the 486 processors, Intel designed the processor to be a user-installable and replaceable part and developed standards for CPU sockets and slots that would allow different models of the same basic processor to plug in.

These specifications were given a designation that is usually imprinted or embossed on the connector or board. If you know the type of socket or slot on your motherboard, you essentially know which type of processors are designed to plug in. Sockets for processors prior to the 486 were not designated, and interchangeability was limited.

Originally, all processors were mounted in sockets (or soldered directly to the motherboard). With the advent of the Pentium II and original Athlon processors, both Intel and AMD shifted to a slot-based approach for their processors because the processors now incorporated built-in L2 cache, purchased as separate chips from third-party Static RAM (SRAM) memory chip manufacturers.

Therefore, the processor then consisted not of one but of several chips, all mounted on a daughterboard that was then plugged into a slot in the motherboard.

This worked well, but there were additional expenses in the extra cache chips, the daughterboard itself, the slot, optional casings or packaging, and the support mechanisms and physical stands and latches for the processor and heatsink. All in all, slot-based processors were expensive to produce compared to the previous socketed versions.

With the advent of the second-generation Celeron, Intel integrated the L2 cache directly into the processor die, meaning within the main CPU chip circuits with no extra chips required.

The second-generation (code named Coppermine) Pentium III also received on-die L2 cache, as did the K6-3, Duron (code named Spitfire), and second-generation Athlon (code named Thunderbird) processors from AMD (some early Thunderbird Athlon CPUs were also made in the Slot A configuration).

With on-die L2, the processor was back to being a single chip again, which also meant that mounting it on a separate board plugged into a slot was expensive and unnecessary. Because of on-die integrated L2 cache, the trend for processor packaging has shifted back to sockets and will likely continue that way for the foreseeable future.

All modern processors now use the socket form. Besides allowing a return to socketed packaging, the on-die L2 cache runs at full processor speed, instead of the one-half or one-third speed of the previous integrated (but not on-die) L2 cache.

The 64-bit Itanium processor from Intel, however, features a cartridge design that includes L3 cache and yet plugs into a socket rather than a slot. Next, we'll discuss about chipset.