Processor SocketsSlots
Processor Sockets/SlotsThe 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. One key was to use a zero insertion force (ZIF) socket design, which meant that the processor could be easily installed or removed with no tools. ZIF sockets use a lever to engage or release the grip on the chip, and with the lever released, the chip can be easily inserted or removed. The ZIF sockets were given a designation that was usually imprinted or embossed on the socket indicating what type it was. Different socket types accepted different families of processors. If you know the type of socket or slot on your motherboard, you essentially know which types of processors are designed to plug in.
Sockets for processors prior to the 486 were not ZIF designs and, as such, were not designed for easy processor installation or removal. In addition, interchangeability was limited. Table 4.9 shows the designations for the various 486 and newer processor sockets/slots and lists the chips designed to plug into them.
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 temporarily 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, processor packaging shifted back to sockets and will continue that way for the foreseeable future. All modern processors now have integrated L2 cache (some also have integrated L3 cache) and 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. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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