Overview
This lecture covers KVM switches—hardware devices that allow control of multiple computers using a single keyboard, video monitor, and mouse. It examines types, technologies, applications, and alternatives.
Introduction to KVM Switches
- KVM stands for keyboard, video, and mouse switch.
- Allows one or more sets of peripherals to control multiple computers.
- Common in data centers and for home setups to share peripherals between devices.
Types of KVM Switch Technologies
- USB Hub Based (Enumerated): Requires USB device re-enumeration each time you switch, causing noticeable latency.
- Emulated USB KVM: Emulates basic keyboard/mouse input for fast switching but supports only basic functions.
- Semi-DDM USB KVM: Supports all USB-HID devices but does not maintain device presence for all systems simultaneously.
- DDM USB KVM: Maintains device presence and special functions for all systems at once, with no switching latency.
- KVM+Dock: Combines KVM switching with docking features, supporting modern working setups.
KVM Switch Features & Operation
- Switches can use rotary knobs, push buttons, or hotkey commands to change computer control.
- Modern KVMs offer on-screen display systems for easier selection.
- Number of supported computers ranges from 2 to over 1,000 in enterprise-grade setups.
Video and Connectivity Considerations
- Most KVMs use VGA, but newer models support HDMI, DisplayPort, and DVI.
- Video bandwidth affects support for high resolutions and refresh rates; advanced KVMs support 4K and beyond.
- KVMs may handle monitor identification (DDC/EDID) via none, fake, or pass-through methods, impacting compatibility.
Passive vs. Active KVM Switches
- Passive (mechanical) switches are simple and cheap but may fail to emulate peripherals properly during boot.
- Active (electronic) switches provide peripheral emulation and can control computers that reboot automatically.
Software Alternatives
- Programs like Synergy and Barrier allow sharing peripherals over a network without physical switches.
Remote KVM Extenders
- Local remote KVMs extend peripheral control up to 300m via direct cabling.
- KVM over IP enables remote management over Ethernet, supporting BIOS-level access and security encryption.
Computer Sharing Devices & Splitters
- KVM splitters work in reverse, allowing multiple sets of peripherals to access one computer.
Key Terms & Definitions
- KVM Switch — Hardware to control multiple computers with one keyboard, monitor, and mouse.
- USB-HID — USB Human Interface Device, e.g., keyboards/mice.
- DDM — Dynamic Device Mapping; maintains individual device functions across computers.
- EDID/DDC — Data protocols for monitor identification and configuration.
- Hot-Key Command — Keyboard shortcut to switch between computers.
- KVM over IP — Remote control of computers via network using a KVM switch.
Action Items / Next Steps
- Review types of KVM switches and their pros/cons.
- Study the chart comparing Hub, Emulated, Semi-DDM, and DDM KVM classes.
- Understand video and monitor compatibility issues for high-resolution setups.