That little sliver of
silicon that you so depend on to bring your daily dose of
E2 is very
fragile. The fine folks at the
CPU factories decided to put it in a casing that would protect them from physical
damage, dissipate heat, and provide a more reasonable electrical connection to the
motherboard.
- DIP The Dual Inline Package chip was used in the very early days of the IBM XT computers. These had two rows of pins running parallel down a plastic package.
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Most integrated chips used this architecture back in those days. Some were fitted into a standard DIP socket, some were soldered to the mainboard. Most manufacturers have moved on to other designs that allow more pins in a smaller package.
- PGA The Pin Grid Array package was used as far back as the Intel 286 computer. They are square, with pins around the perimeter. The ceramic-based ones are called CPGA and the plastic versions are called PPGA. The plastic version is cheaper and transfers heat faster, so it is used more in later model CPUs.
When Intel had to pack around 300 pins in a small space, they came up with the staggered-PGA (SPGA). The original Pentium CPUs used this, and when the Pentium Pro came out, they modified it to a dual-pattern pin array to take into account the special on-chip L2 cache. The latest versions of the PGA runs over 400 pins on one chip, and the cooling is critical now (mere seconds to kill a CPU without the heatsink).
- SEC Single-Edge Contact packaging moved the L2 cache off of the chip onto a daughterboard. These sometimes go by the name Socket A or Slot 1 CPUs. The CPU chip itself uses a type of PGA system, but allows the chip to connect to the L2 cache for high-speed transfers. There are adapters for standard PPGA CPUs to allow them to be used in Slot 1 mainboards.
- MMO Mobile MOdule CPUs are made for power-frugal portables and notebook computers. These packages combine the silicon CPU, the L2 cache and the supporting chipset onto one easily-mounted module. The interface allows fast transfers and tight integration of the CPU and mainboard chipset.
- TCP Tape Carrier Packaging are made for some portable CPU applications. The raw chips come on a long roll without external packaging, and are soldered to special mainboards. It takes up less space, which is at a premium on portables.
netsharc says re: CPU Packaging, actually, Socket A is also PGA, Slot A is AMD's version of the SEC, with quite interesting politics that made both companies switch from socket to SEC to socket again.