computer science

KVM switch

KVM switch is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand KVM switch rather than just read about it. In short: A KVM switch (with KVM being an abbreviation for "keyboard, video, and mouse") is a hardware device that allows a user to control multiple computers from one or more sets of keyboards, video monitors, and mice. Name Switches to connect multiple computers to one or more peripherals have had multiple names.

Key takeaways

KVM switch belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect KVM switch to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of KVM switch from memory before moving on to harder problems.

Reference excerpt

Name Switches to connect multiple computers to one or more peripherals have had multiple names. The earliest name was Keyboard Video Switch (KVS). With the advent of the mouse, the Keyboard, Video and Mouse (KVM) switch became popular. The name was introduced by Remigius Shatas, the founder of Cybex (now Vertiv), a peripheral switch manufacturer, in 1995. Some companies call their switches Keyboard, Video, Mouse and Peripheral (KVMP).

Types

USB keyboards, mice, and I/O devices are the most common devices connected to a KVM switch. The classes of KVM switches discussed below are based on different types of core technologies, which vary in how the KVM switch handles USB I/O devices—including keyboards, mice, touchscreen displays, etc. (USB-HID = USB human interface device)

USB hub-based KVM Also called an Enumerated KVM switch or USB switch selector, a connected/shared USB device must go through the full initiation process (USB enumeration) every time the KVM is switched to another target system/port. The switching to different ports is similar to the process of physically plugging and unplugging a USB device into the targeted system. Emulated USB KVM Dedicated USB console port(s) are assigned to emulate special sets of USB keyboard or mouse switching control information to each connected/targeted system. Emulated USB provides an instantaneous and reliable switching action that makes keyboard hotkeys and mouse switching possible. However, this class of KVM switch only uses generic emulations and consequently has only been able to support the most basic keyboard and mouse features. There are also USB KVM devices that allow cross-platform operating systems and basic keyboard and mouse sharing. Semi-DDM USB KVM Dedicated USB console port(s) work with all USB-HID (including keyboard and mouse), but do not maintain the connected devices' presence to all of the targeted systems simultaneously. This class of KVM takes advantage of DDM (Dynamic Device Mapping) technology. DDM USB KVM Dedicated Dynamic Device Mapping USB console port(s) work with all USB-HID (including keyboard and mouse) and maintain the connected devices' special functions and characteristics to each connected/targeted system. This class of KVM switch overcomes the frustrating limitations of an Emulated USB Class KVM by emulating the true characteristics of the connected devices to all the computers simultaneously. This means that it is now possible to use the extra function keys, wheels, buttons, and controls that are commonly found on modern keyboards and mice. KVM+Dock A KVM switch with built-in docking station. It combines two devices, a KVM switch and a docking station. The customer expectations for this kind of product has increased due to a rising number of work-from-home setups that need to share user I/O devices between a personal PC and work laptop as a consequence of COVID pandemic restrictions.

Limited* supported, but does not allow USB re-enumeration, which not only causes long delays in switching, but also sometimes causes HPD (Hot-Plug Device) errors to the OS system(s). Yes* Latency time within 1 second while switching between channels/ports. KVM+Dock Dual DP1.4 KVM switch with TB4 dock model will be the first model released for full-buss DisplayPort 1.4 sharing for 4K144hz gaming monitors.

Use A KVM Switch is a hardware device used in data centers that allows the control of multiple computers from a single keyboard, monitor and mouse (KVM). The switch allows data center personnel to connect to any server in the rack. A common example of home use is to enable the use of the full-size keyboard, mouse and monitor of the home PC with a portable device such as a laptop, tablet PC or PDA, or a computer using a different operating system. KVM switches offer different methods of connecting the computers. Depending on the product, the switch may present native connectors on the device where standard keyboard, monitor and mouse cables can be attached. Another method to have a single DB25 or similar connector that aggregated connections at the switch with three independent keyboard, monitor and mouse cables to the computers. Subsequently, these were replaced by a special KVM cable which combined the keyboard, video and mouse cables in a single wrapped extension cable. The advantage of the last approach is in the reduction of the number of cables between the KVM switch and connected computers. The disadvantage is the cost of these cables. The method of switching from one computer to another depends on the switch. The original peripheral switches (Rose, circa 1988) used a rotary switch while active electronic switches (Cybex, circa 1990) used push buttons on the KVM device. In both cases, the KVM aligns operation between different computers and the users' keyboard, monitor and mouse (user console). In 1992–1993, Cybex Corporation engineered keyboard hot-key commands. Today, most KVMs are controlled through non-invasive hot-key commands (e.g. Ctrl+Ctrl, Scroll Lock+Scroll Lock and the Print Screen keys). Hot-key switching is often complemented with an on-screen display system that displays a list of connected computers. KVM switches differ in the number of computers that can be connected. Traditional switching configurations range from 2 to 64 possible computers attached to a single device. Enterprise-grade devices interconnected via daisy-chained and/or cascaded methods can support over 1,000 devices equally accessed by any given user console.

Video bandwidth

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with KVM switch

Start with the simplest possible case. Write down what KVM switch claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to KVM switch before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about KVM switch ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of KVM switch

In research: KVM switch appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses KVM switch in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: KVM switch is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer connectors, Computer peripherals, Input/output, so understanding it makes those chapters shorter.
In everyday life: Look for KVM switch outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study KVM switch in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what KVM switch means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain KVM switch out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is KVM switch in simple terms?

A KVM switch (with KVM being an abbreviation for "keyboard, video, and mouse") is a hardware device that allows a user to control multiple computers from one or more sets of keyboards, video monitors, and mice. Name Switches to connect multiple computers to one or more peripherals have had multiple…

Why does KVM switch matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study KVM switch?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on KVM switch.