Some general information about the 8088 CPU :

8088 CPU Overview

CPU Speed :         4.77 MHz to 10 MHz – Up to 16Mhz on the NEC V20
Transistors:           29,000
Data width:            8 Bit
Address width       20 Bit
Socket:                  DIP40


The Intel 8088 microprocessor was released in 1979, or one year after the Intel 8086 CPU. Both processors have the same architecture, and the only difference of the 8088 CPU from the 8086 is the external data bus width – it was reduced from 16 bits to 8 bits.

The 8088 CPU uses two consecutive bus cycles to read or write 16 bit data instead of one bus cycle for the 8086, which makes the 8088 processor to run slower. On the plus side hardware changes to the 8088 CPU made it compatible with 8080/8085 support chips. This was an important factor in choosing the 8088 processor for IBM PC line of computers because at that time 8-bit support chips were cheaper than 16-bit support chips, and there was better selection of 8-bit chips.

The 8088 microprocessor has 16-bit registers, 16-bit internal data bus and 20-bit address bus, which allows the processor address up to 1 MB of memory. The 8088 uses the same segmented memory addressing as the 8086: the processor can address 64 KB of memory directly, and to address more than 64 KB of memory the CPU has to break the update into a few parts – update up to 64 KB of memory, change segment register, update another block of memory, update segment register again, and so on.

Like to 8086, the 8088 microprocessor supports Intel 8087 numeric co-processor. The CPU recognizes all Floating-Point (FP) instructions, and, when necessary, it calculates memory address for FP instruction operand and does a dummy memory read. The FPU captures the calculated address and, possibly, the data, and proceeds to execute FP instruction. The CPU at the same time starts executing the next instruction. Thus, both integer and floating-point instructions can be executed concurrently.

Original Intel 8088 microprocessor was manufactured using HMOS technology. There were also CMOS versions of the chip – 80C88 and 80C88A. These microprocessors had much lower power consumption and featured standby mode.

The original IBM PC was the most influential microcomputer to use the 8088. It used a clock frequency of 4.77 MHz.

IBM chose the 8088 over the 8086 because Intel offered a better price for the former and could supply more units. Another factor was that the 8088 allowed the computer to be based on a modified 8085 design, as it could easily interface with most nMOS chips with 8-bit data buses.

Variants of the 8088 with more than 5 MHz maximal clock frequency include the 8088-2, which was fabricated using Intel’s new enhanced nMOS process called HMOS and specified for a maximal frequency of 8 MHz.

Later followed the 80C88, a fully static CMOS design, which could operate with clock speeds from 0 to 8 MHz. There were also several other, more or less similar, variants from other manufacturers. For instance, the NEC V20 was a pin-compatible and slightly faster (at the same clock frequency) variant of the 8088, designed and manufactured by NEC.

Successive NEC 8088 compatible processors would run at up to 16 MHz.

When announced, the list price of the 8088 was US$124.80



Project 8088 - The 8088 CPU General Information

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Project 8088 - The 8088 CPU General Information