Intel 8088

The Intel 8088 ("eighty-eighty-eight", also called iAPX 88) microprocessor is a version of the Intel 8086. It was introduced on June 1, 1979. One big difference between the 8088 and the 8086 is that the 8088 uses an eight-bit external data bus instead of a 16-bit bus. This made it cheaper and easier to build computers with.

Even with this change, the 8088 kept the same powerful features as the 8086. It had 16-bit registers and could address up to one megabyte of memory. The parts of the chip that handles calculations worked exactly the same. Only the part that connects to other parts of the computer was different.

Because of these advantages, the 8088 became very important in history. It was the brain of the original IBM PC and many computers that tried to act like the IBM PC. This helped start the era of personal computing that we still use today.

History and description

The 8088 was made at Intel's lab in Haifa, Israel, like many of Intel's processors. It was a cheaper version of the 8086, using an eight-bit data path to save costs. At the time, complex circuit boards were expensive, so this design helped make computers more affordable. The 8088 had some changes to its design office in Haifa.

There were different versions of the 8088, such as the 8088–2, which could run up to 8 MHz. Later came the 80C88, which could run between 0 to 8 MHz. Other companies made similar processors, like NEC's V20, which was a bit faster. Commodore International planned to use the 8088 in a clone called the Dynalogic Hyperion. The 8088 was introduced for $124.80, but later a plastic version cost $14.10 for 100 units. Intel also allowed other companies like Fujitsu to make the 8088.

Differences from the 8086

The 8088 was very similar to the 8086 but had eight data lines instead of 16. This changed two pins: pin 34 no longer selected the high-order byte, and the IO/M pin was reversed to work better with other chips.

Performance

The 8088's performance ranged from 0.33 to 1 million instructions per second, depending on its speed and the program. Because it had an eight-bit bus, it was slower than the 8086, often running about half as fast at the same clock speed. This made the order of instructions important for speed. The 8088 also struggled with memory access, making it slower to get data from memory than from registers.

Selection for use in the IBM PC

The original IBM PC used the 8088, running at 4.77 MHz. IBM chose it over other processors because Intel offered a better price and could supply more units. The 8088 also fit well with existing 8-bit components, making the PC design more economical. The 8088 led to many later processors, including today's Intel Core processors.

Peripherals

The Intel 8088 microprocessor worked with several supporting chips to handle different tasks. These included the Intel 8237 for managing direct memory access, the Intel 8253 for timing functions, and the Intel 8255 for connecting to peripheral devices like printers. Other important chips were the Intel 8259A for handling interrupts, the Intel 8288 for bus control, and the Intel 8289 for managing bus access. The Intel 8087 acted as a math co-processor to help with complex calculations.