The most reliable way to get GNS3-compatible images is by purchasing a CML Personal License ($199/year). This grants you access to IOSvL2 (Layer 2 Switch) and IOSv (Layer 3 Router) images, which are the industry standard for GNS3 labs.
The Cisco Catalyst 4500 series switch in GNS3 because its proprietary Application-Specific Integrated Circuits (ASICs) cannot be simulated by standard computer processors. cisco 4500 switch ios download for gns3
If you do not set an Idle-PC value, your CPU usage will spike to 100%. The most reliable way to get GNS3-compatible images
This is the gold standard for GNS3 today. It is a virtualized switch image originally from Cisco CML (Cisco Modeling Labs). It supports advanced features like EtherChannels, Spanning Tree variations, and Layer 3 routing that mimic 4500 behavior. Cisco IOU/IOL (The Lightweight Choice): Spanning Tree variations