Microprocessor 1971 Step 14 Successor 8008 Quick Second Microprocessor
# The Quick Successor: Why the 8008 Shipped Within a Year and Changed the Target Customer
## 1. A Second Chip Whose Origin Predates the First One's Release
Intel's 8008, announced in April 1972, is often described loosely as "the next microprocessor after the 4004," which understates how closely the two projects actually overlapped. The 8008's architecture traces to a 1969 request from Computer Terminal Corporation (CTC), which wanted a processor for an intelligent terminal — a request Intel was evaluating in parallel with the Busicom calculator work this series' Step 11 describes, using some of the same silicon-gate PMOS techniques Step 12 attributes to Faggin. CTC's own project stalled, and Intel — already holding the rights to the design under a similar buy-back arrangement to the one it negotiated with Busicom — released the chip itself once the 4004 had proven that a general-purpose processor could be sold as a catalog part.
The 8008 was not a scaled-up 4004 in any simple sense. It used an eight-bit word instead of the 4004's four-bit word, addressed more memory, and targeted a different class of customer — one needing enough computing capability to run a terminal's control logic, not a four-function calculator's arithmetic.
## 2. Why the Target Customer Changed the Architecture, Not Just the Word Width
Step 2 of this series shows the 4004's four-bit word as a deliberate pin-and-transistor-budget compromise suited to a calculator's own data widths — binary-coded decimal digits, four bits each. The 8008's eight-bit word reflects a different customer requirement: terminal logic handling ASCII character codes, which need a full byte, and a wider range of memory addresses than a calculator's working set ever required. The word-width decision Step 2 frames as a budget tradeoff recurs here with a different budget and a different answer, because the customer changed, not because Intel had learned the 4004's word width was a mistake.
This matters for how the two chips should be read together: the 8008 is not a correction of the 4004's architecture, and the 4004 is not an obsolete prototype of the 8008. Each is the right-sized answer to a distinct customer's own requirement, using a shared design methodology — silicon-gate PMOS, mask-programmed ROM companions, a fetch-decode-execute control loop — that this series' earlier steps already established as reusable across applications.
## 3. The 8008's Place in This Series' Own Arc
This step does not extend the 4004's own technical account — the 4004's arithmetic, decoding, and timing described in Steps 1 through 10 remain complete and unmodified. What it adds is the observation that the 4004 was not a one-off: Intel had a second general-purpose design already in motion through an independent customer relationship, and the 4004's commercial success was the signal that let Intel release that second design as a catalog part too, rather than let it remain dormant the way CTC's own stalled terminal project had left it. The 8008, not the 4004 directly, became the architectural basis for Intel's later 8080 and, through it, the much wider x86 line — a lineage this series does not trace further, since it departs from the 4004's own specific MCS-4 family that Step 10 classifies.