A few years ago I undertook a project to overclock my TI-83+ calculator. The objective was to increase processing speed without causing permanent damage. While similar modifications have been documented for other TI-83+ revisions, my Rev A board differed enough that I needed to determine the processor pinout and clock circuitry on my own.

The project focused on modifying the calculator's clock signal to achieve higher operational frequency. The processor is a Zilog Z80-based Inventec 6S1837. Understanding its RC oscillator clock generation and carefully selecting timing components were essential to achieving a stable overclock.

The core modification involved replacing the original timing capacitor with a switched configuration. When the switch is off, the calculator retains the original capacitor and operates at standard speed. When the switch is on, a smaller capacitor is introduced, increasing the clock frequency.

Choosing appropriate capacitor values required iterative testing. Excessive frequency caused the processor to output to the display faster than it could reliably update, resulting in visual glitches. After a series of tests, a stable frequency range was identified that improved performance without affecting the display.

This project provided hands-on experience in low-level hardware modification, circuit analysis, and iterative troubleshooting. By examining the Rev A board and the Z80-based processor, I was able to implement a reliable overclock with precise control over the clock frequency. The project highlights the impact of small component changes on system performance and demonstrates a methodical approach to hardware modification.

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MD (2020)