Socket & Slot Types in the First Microprocessor

Intel created the first microprocessor, called 4004, in 1971; the company manufactured the chip through 1971 to 1981. It wasn't until a decade after the invention of the CPU that IBM created the first personal computer, but despite the existence of the 4004, IBM installed a more recent microprocessor -- the Intel 8088, created in 1979 -- in the original PC.

Basics

The 4004 was a 4-bit CPU that processed data at a speed of 740 kilohertz, or 740,000 cycles per second. Unlike the Intel 8088, the 4004 wasn't used in PCs, but was found in traffic light controllers and other programmable devices, as well as calculators; the first product to use the 4004 was the Busicom 141-PF high-performance calculator. The 4004 also appeared in high-profile computers, like Voyager 1, a space probe NASA launched in 1977.

Packaging

The Intel 4004 didn't connect to a motherboard in the same manner as modern CPUs do. Unlike today's microprocessors, which install to a square-shaped mounted socket, the 4004 was contained in a chip called a dual in-line package, or DIP, that plugged into through-holes on the motherboard. The CPU was made up of two rows of eight pins and used what's referred to as a DIP16 package -- 16 referring to the number of total pins on the DIP.

PC Processing

The Intel 8088 also used a DIP, although the processor had 40 pins instead of 16. The 8088, a lower-end derivative of the 8086 released a year prior, used a 16-bit instruction set and had a clock speed of 5 to 10 megahertz. Unlike the 4004, the 8088 was able to use a level 1 cache, which holds data that the computer thinks the processor will need. The L1 cache enabled the first PC to access data faster than previous computers, which retrieved all active data from the memory.

Socketing

The first modern socket was Socket 1, also known as OverDrive. It supported the first mainstream microprocessor, the Intel 80486, also known as the i486, which was developed in 1989. Unlike the 4004 and the 8088, the i486 used packaging called a pin grid array -- its name referring to the manner in which the pins were organized on the processor chip. The i286 and i386, developed prior to the i486, also used PGA packaging to connect to the motherboard, but the slots that microprocessors plugged into weren't established socket specifications.

References

• Upgrading and Repairing PCs; Scott Mueller
• The Intel 4004 Home
• PCGuide: Intel Socket 1 Specification