History of PCs – Clock Speed of the Original IBM PC (Model 5150) What was the approximate CPU clock speed shipped with the first IBM PC when it debuted?

Introduction / Context:
Understanding early PC hardware provides perspective on today’s vastly faster systems. The original IBM PC (model 5150) set many standards for the personal computing era, including CPU type and clock speed, influencing software design and performance expectations of the time.

Given Data / Assumptions:

• Question refers to the original IBM PC released in 1981.
• The CPU was Intel 8088, a variant of the 8086 with an 8-bit external data bus.
• We must identify the nominal factory clock speed.

Concept / Approach:
The IBM 5150 shipped with an Intel 8088 running at approximately 4.77 MHz. This frequency arose from dividing a 14.31818 MHz crystal (related to NTSC color burst frequency) by 3. Early software and operating systems (like PC-DOS) were engineered around this baseline speed.

Step-by-Step Solution:

Verification / Alternative check:
Historical specifications, service manuals, and retro-computing references list 4.77 MHz as stock speed. Many later clones or Turbo modes provided higher speeds (for example, 8 MHz), but the original baseline was under 5 MHz.

Why Other Options Are Wrong:

• 10 MHz / 8 MHz: Seen in later XT-class “turbo” systems or compatibles, not the launch configuration.
• Just over 16 MHz: Much later for 80286/80386 class machines; not applicable to the 8088-based 5150.

Common Pitfalls:
Confusing later IBM PC/XT or clone enhancements with the specifications of the very first IBM PC, or assuming the 8086’s variants always shipped near 8–10 MHz in 1981.

Final Answer:
Less than 5 MHz