# Inside a Mystery 1980s Filter IC Featuring Switched Capacitors

> **Key Architectural Takeaway:** Recently [Ken Shirriff] got handed a mystery IC by [CuriousMarc] who had found said IC in a box of various old chips.

**Published:** 2026-10-11T14:00:45+00:00  
**Source:** Hackaday Hardware  
**Category:** open-hardware  
**Canonical URL:** https://fosswire.org/news/inside-a-mystery-1980s-filter-ic-featuring-switched-capacito.html  

## Executive Summary
Recently [Ken Shirriff] got handed a mystery IC by [CuriousMarc] who had found said IC in a box of various old chips. Labelled only with a date code of the 47th week of 1985 and a mysterious F1-10-5 alongside a logo that didn’t lead to any hits in the typical IC databases, it was up to [Ken] to figure out what lurks inside this CDIP chip. As it turns out, it’s actually a pretty interesting IC with an easy to identify die once the ceramic package had been cracked open with a surgical hammer-and-chisel strike.

## Architectural & Systems Analysis
From a silicon and hardware engineering viewpoint:

- **Interface Neutrality:** Mitigates dependency on proprietary BSPs, empowering open toolchains to address hardware directly.
- **Supply Chain Verification:** Schematics and open pinouts allow deterministic audits against silicon errata.
- **Lifecycle Decoupling:** Decouples physical hardware utility from commercial vendor end-of-life obsolescence.

## Impact on the Open Ecosystem
Ensures that computational autonomy remains in the hands of the architect rather than closed silicon vendors.