One of the big decisions IBM made in creating the original IBM PC was choosing to use the Intel 8088 processor as its central processing unit (CPU). This turned out to be hugely influential in establishing the Intel architecture—often called the x86 architecture—as the standard for the vast majority of the personal computer industry. But there are many stories around how the decision was made.

Up to that point, pretty much all the popular personal computers had run 8-bit processors. This included the Intel 8080 that was in the MITS Altair 8800 (the machine that led to Bill Gates and Paul Allen creating the first PC BASIC and then to the founding of Microsoft); the Zilog Z80, a chip that offered compatibility with the 8080 along with a variety of improvements and was used in the Osborne 1, Kaypro II and many other CP/M-based machines; and the MOS Technology 6502, which was used in the Apple II and the Commodore PET.

Intel followed its 8080 with the 8-bit 8085 and introduced the 16-bit 8086 in 1978. That was followed by the 8088, which had the same 16-bit internal architecture but was connected to an 8-bit data bus, in 1979. Meanwhile, some other more advanced chips were coming to market, such as the Motorola 68000 with 32-bit instructions, which was introduced in 1979 and would later be the processor in Apple's Lisa and Macintosh, Commodore Amiga, and a number of UNIX-based workstations. Both Gates and Allen say Microsoft talked IBM out of using an 8-bit processor and moving instead to the 16-bit 8088. //

Allen and Gates certainly believe that Microsoft led IBM to make that decision, but the IBM team tells a somewhat different story.

Dave Bradley, who wrote the BIOS (basic input output system) for the IBM PC, and many of the other engineers involved say IBM had already decided to use the x86 architecture while the project was still a task force preparing for management approval in August 1980.

In 1990, Bradley told Byte there were four reasons for choosing the 8088. First, it had to be a 16-bit chip that overcame the 64K memory limit of the 8-bit processors. Second, the processor and its peripheral chips had to be immediately available in quantity. Third, it had to be technology IBM was familiar with. Fourth, it had to have available languages and operating systems.

That all makes sense in leading to the decision for the 8086 or 8088. Newer chips like the Motorola 68000 didn't yet have the peripheral chips ready in the summer of 1980. And IBM was very familiar with the Intel family; indeed, Bradley had just finished creating control software for the IBM DataMaster, which was based on the 8-bit 8085. Bradley said IBM chose the 8088 with the 8-bit bus because it saved money on RAM, ROM, and logic chips.

Big Blues: The Unmaking of IBM, by Paul Carroll, suggests the PC team picked the 8-bit version because using a full 16-bit processor might have caused IBM's Management Committee to cancel the project for fear of hurting sales of its more powerful products. Bill Syndes, who headed hardware engineering for the project, has said similar things in a few interviews.