Cirrus Logic produced many video chipset
s for PCs during the 1990s. They were primarily low-end VGA
chipsets based on the ISA
bus and were common as entry-level graphics
accelerators in inexpensive systems.
The most common was the CL-GD542x series, which was reasonably fast, cheap (around $20 for a 1MB card in 1994) and accelerated under Windows 3.1. These cards were also well-supported by XFree86 at the time.
Millions were sold; if you find an old 80486 sitting around, chances are it has an STB Horizon 64 or similar Cirrus-based video board in it.