KVM Switch

Chapter 14 — KVM Switch

A KVM switch (Keyboard, Video, Mouse) lets two or more PCs share the same monitors, keyboard, and mouse. One button press — or a keyboard shortcut — switches everything simultaneously. For a desk with three monitors and a second machine worth keeping, it eliminates the cable-swapping that otherwise makes using both machines impractical.

Your situation in one sentence: New LGA1700 machine is the primary workstation. The old i5-10400 machine (on integrated graphics after the RTX 3050 LP moved over) is a useful second PC for testing, legacy software, or a dedicated task machine — but only if you can switch to it without touching cables.

What a KVM Switch Does

WITHOUT KVM — Cable-swap every time New PC ──────────────────────────────────────────── Monitor 1 New PC ──────────────────────────────────────────── Monitor 2 New PC ──────────────────────────────────────────── Monitor 3 (165Hz) New PC ──────────────────────────────────────────── Keyboard New PC ──────────────────────────────────────────── Mouse Old PC (disconnected — too much hassle to swap) WITH KVM — One keypress switches everything New PC ──→ KVM ──→ Monitor 1 (60Hz) Old PC ──→ KVM ──→ Monitor 2 (60Hz) │ ├──→ Keyboard (shared — follows the active PC) └──→ Mouse (shared — follows the active PC) New PC ──────────────────────────────────────────── Monitor 3 (165Hz, direct) Press Scroll Lock × 2 → everything switches to Old PC in <1 second

The KVM sits between your PCs and your peripherals. Each PC has its own set of cables going into the KVM's input ports. The KVM's output ports connect to your monitors, keyboard, and mouse. When you switch, the KVM re-routes all signals simultaneously — the monitors show the other PC's desktop, and the keyboard and mouse now control it.

The 165Hz Problem — Why Monitor 3 Stays Direct

Never run your 165Hz monitor through a KVM switch. Most KVM switches — including expensive ones — cap DisplayPort output at 4K@60Hz or 1440p@60Hz. Even models that advertise higher refresh rates often can't reliably pass the full DP 1.4 signal needed for 165Hz at 1440p. You would pay a significant premium for a specialised unit, and the 2024 Samsung's 165Hz would silently drop to 60Hz the moment it goes through a cheap or mid-range KVM.

The practical solution is straightforward: leave Monitor 3 permanently connected directly to the new PC. It only ever shows the new machine's output. The KVM handles Monitors 1 and 2 (both 60Hz, which every KVM supports without issue). This approach:

Preserves 165Hz on the monitor that has it, always
Costs significantly less — a dual-monitor KVM is £60–150 vs £300+ for a reliable triple-monitor unit
Is simpler to wire and more reliable in practice
Matches real usage — when you're on the old PC, you'll use two monitors; the third sitting dark is fine

The old machine on integrated graphics: The i5-10400 has Intel UHD 630 integrated graphics. With the RTX 3050 LP now in the new machine, the old PC uses iGPU output via the B560M PRO-E's rear panel — typically 1× HDMI 2.0 and 1× DisplayPort 1.2. This comfortably drives two monitors at 1080p@60Hz, which is exactly what you need for the KVM setup.

Recommended Wiring — Your Specific Setup

RECOMMENDED SETUP — Dual KVM + Direct 165Hz ┌──────────────────────────────┐ NEW PC │ DisplayPort ──→ [Monitor 3] │ 165Hz Samsung 2024 (RTX 3050 LP) │ DIRECT │ NEVER through KVM │ │ │ DisplayPort ──→ ┌──────────┐ │ │ │ │ │ OLD PC │ DisplayPort ──→ │ 2-port │ ──→ [Monitor 1] ~2015 Samsung 60Hz (Intel UHD 630) │ or HDMI │ KVM │ │ │ Switch │ ──→ [Monitor 2] ~2019 Samsung 60Hz │ │ │ │ │ USB-A ───┤ ──→ Keyboard │ │ USB-A ───┤ ──→ Mouse │ └──────────┘ └──────────────────────────────┘ Switching: Scroll Lock, Scroll Lock (or dedicated button on KVM) Result: Monitor 1 + 2 + keyboard + mouse switch to Old PC Monitor 3 always shows New PC Old PC RAM note: The i5-10400 machine needs its own RAM after the build. A 2× 8GB DDR4-2400 kit costs ~£20–30 and is all iGPU needs.

KVM Buying Guide — What Specs Actually Matter

Number of Ports (PCs)

2-port for this build

You have two machines. 4-port KVMs cost more and often have worse signal quality per port. A 2-port unit is simpler, cheaper, and more reliable.

Number of Monitors

Dual-monitor (2 displays)

After removing Monitor 3 from the KVM loop, you only need 2 display ports on the KVM — dramatically cheaper and more reliable than a triple-monitor unit.

Video Connector Type

DisplayPort preferred

Your monitors likely have HDMI and/or DisplayPort. Confirm which inputs Monitors 1 and 2 have before buying. DP KVMs support higher resolutions without adaptors. HDMI KVMs are slightly cheaper.

Max Resolution & Refresh

1080p or 1440p @ 60Hz

Your two 60Hz monitors need nothing beyond 1080p@60Hz or 1440p@60Hz. Almost every modern KVM handles this. Don't pay for 4K@144Hz capability you won't use on these displays.

USB Ports

4× USB-A minimum

2 ports for keyboard and mouse. Extra USB ports on the KVM act as a shared USB hub — useful for a desk webcam, USB hub, or audio interface that both PCs can reach.

USB Version

USB 3.0 if possible

USB 3.0 on the KVM matters if you connect a shared storage device or webcam. For keyboard and mouse only, USB 2.0 is perfectly adequate. Most modern KVMs mix USB 3.0 and 2.0 ports.

Hotkey Switching

Scroll Lock × 2 standard

The near-universal KVM hotkey is pressing Scroll Lock twice quickly. Better units let you remap this. Some have a physical button on the unit itself as an alternative — useful if the hotkey conflicts with a game or application.

EDID Emulation

Essential — confirm before buying

EDID (Extended Display Identification Data) tells the PC what monitors are connected. Without EDID emulation, switching away from a PC causes it to "lose" the monitors — windows get rearranged and resolutions reset. Every quality KVM includes this; cheap ones often don't.

Audio Passthrough

Optional but convenient

Some KVMs include 3.5mm audio ports so your speakers/headphones also switch with the active PC. Useful if you use a single desk speaker set. Not needed if audio is handled separately (USB DAC, Bluetooth headphones, etc.).

EDID emulation is non-negotiable: Without it, every time you switch to the other PC, Windows thinks the monitors were disconnected. It moves all your open windows to whichever monitor it assumes is still active and resets display settings. You spend 30 seconds reorganising your workspace after every switch. Good KVMs with EDID emulation keep each PC's monitor layout frozen exactly as you left it.

What Makes a Good KVM vs a Bad One

EDID emulation on all video ports
DisplayPort 1.2 or 1.4 (not "DP-compatible" generic)
Named brand: ATEN, Level One, TESmart, Club 3D
USB 3.0 on at least 2 ports
Remappable hotkey (or physical button alternative)
Works without drivers (class-compliant USB)
Consistent user reviews mentioning EDID specifically
Explicit max resolution per port in the spec sheet

No mention of EDID emulation anywhere in the listing
"Supports up to 4K" with no refresh rate specified
Unbranded / no-name units under £25
Requires proprietary software or drivers to function
Only USB 2.0 on all ports (limits shared devices)
Reviews mentioning windows moving on switch
VGA or DVI outputs (obsolete — adaptors cause EDID issues)
"HDMI 2.0 compliant" without explicit bandwidth spec

Recommended KVM Switches — For This Setup

Ports2 PCs × 2 Monitors

VideoDisplayPort 1.2

Max resolution4K@60Hz / 1080p@120Hz per port

EDID emulationYes — built-in

USB4× USB 3.1 shared hub

Audio3.5mm in + out (switches with PC)

HotkeyScroll Lock × 2 or front button

Drivers neededNo — plug and play

ATEN is the benchmark brand for KVM switches. The CS1922M is their mainstream dual-DP model — solid EDID implementation means zero window-rearrangement on switch. USB 3.1 hub is fast enough for a shared external SSD. Well-reviewed over several years.

~£130 – £180

Ports2 PCs × 2 Monitors

VideoDisplayPort 1.4

Max resolution4K@144Hz or 1080p@240Hz

EDID emulationYes

USB4× USB (mix of 3.0 and 2.0)

Audio3.5mm passthrough

HotkeyScroll Lock × 2 or physical button

DP 1.4 future valueHandles higher refresh if monitors upgrade

TESmart has become a credible mid-range KVM brand. DP 1.4 gives more headroom than you need right now, which makes this a better long-term buy if you ever upgrade Monitors 1 or 2 to 1440p@144Hz. Slightly lower price than ATEN with similar feature set.

~£90 – £130

Ports2 PCs × 2 Monitors

VideoHDMI 2.0

Max resolution4K@60Hz / 1080p@60Hz

EDID emulationCheck listing carefully

Typical brandsNewyes, UGREEN, KVM-Tek

AudioSometimes, sometimes not

RiskVariable EDID quality

If both 60Hz monitors only have HDMI inputs, an HDMI dual-monitor KVM costs significantly less. Read reviews specifically for EDID behaviour before buying — the savings evaporate if you spend time fixing window layouts after every switch.

~£40 – £80

Before you buy — check your two 60Hz monitors' inputs: The 2015 Samsung may only have HDMI or DVI; the 2019 Samsung likely has both HDMI and DisplayPort. Knowing exactly what inputs each monitor has determines whether you need a DP KVM, an HDMI KVM, or a mixed unit. Check the sticker on the back of each monitor for the model number and look up the spec sheet.

Installing and Configuring the KVM

Plan your cable run before connecting anything

The KVM needs to sit somewhere accessible — ideally on or near the desk where the physical button is reachable. Measure cable runs from: (a) new PC to KVM, (b) old PC to KVM, (c) KVM to Monitor 1, (d) KVM to Monitor 2. KVMs typically include short cables (1–1.5m) which may not reach from two different PC locations. Budget for longer cables if needed — DisplayPort cables up to 2m are inexpensive and reliable.

Connect Monitor 3 (165Hz) directly to the new PC first

Connect the 2024 Samsung to the new PC's RTX 3050 LP using a DisplayPort cable directly — this connection goes nowhere near the KVM. Boot the new PC and confirm Monitor 3 is working at 165Hz via Display Settings before touching the KVM wiring. This baseline confirms the monitor works before you introduce the KVM into the signal path for the other two.

Use one of the RTX 3050 LP's three DisplayPort outputs for Monitor 3 and reserve HDMI for the KVM chain if one of the 60Hz monitors only has HDMI input.

Connect both PCs to the KVM's input ports

Use the KVM-supplied cables or your own. KVM Port 1 → New PC (RTX 3050 LP outputs). KVM Port 2 → Old PC (B560M PRO-E rear I/O video outputs). Also connect the USB cables: each PC sends a USB upstream cable to the KVM — this is what lets the KVM route keyboard and mouse between machines. These USB upstreams are usually Type-B (square) connectors going into the KVM and Type-A going into a USB port on each PC.

Use a DP output on the old PC that matches the KVM's input type. The B560M PRO-E has 1× HDMI 1.4 and 1× DisplayPort 1.2 on the rear I/O — use the DP output for better compatibility with a DP KVM. If the KVM is HDMI, use the HDMI output.

Connect KVM outputs to Monitors 1 and 2

The KVM has output (console) ports for displays — connect these to Monitors 1 and 2. On a dual-monitor KVM, there are two video output ports labelled "Monitor 1" and "Monitor 2" (or A/B). Connect them consistently: always Monitor 1 goes left, Monitor 2 goes centre (or whatever arrangement matches your physical layout).

Label each cable with a small sticky note during installation — KVM wiring is easy to mix up when there are 8+ video cables going in similar directions. You'll thank yourself the first time you need to trace a cable.

Connect keyboard and mouse to the KVM's shared USB ports

Plug the keyboard and mouse into the KVM's console USB ports (not into a PC directly). These are the ports that switch with the active PC. Most KVMs have 2–4 USB-A ports on the front or side labelled "Console" or with a keyboard/mouse icon. Your keyboard and mouse should still work exactly as before — but now they follow whichever PC is selected.

Test switching and verify EDID behaviour

Power on both PCs. Press Scroll Lock × 2 to switch. Verify: (a) Monitors 1 and 2 show the other PC's desktop immediately, (b) keyboard input now goes to the other PC, (c) when you switch back, your open windows on the first PC are exactly where you left them (EDID emulation working). Open a text editor on each PC and type a few characters to confirm keyboard routing.

If windows rearrange on switch, EDID emulation isn't working. Check the KVM's manual for an EDID mode toggle — many units have it disabled by default and require a specific button combination to enable it.

USB Sharing — What Switches and What Doesn't

Device	Connection Method	Behaviour on Switch
Keyboard	Console USB port on KVM	Switches — follows the active PC
Mouse	Console USB port on KVM	Switches — follows the active PC
USB hub (shared)	Console USB port on KVM	Switches — hub and all its devices switch together
Webcam	Console USB port	Switches — active PC gets webcam; other PC loses it
Headphones/speakers	KVM 3.5mm audio jack (if present)	Switches with PC selection
USB DAC / audio interface	Console USB port	Switches — only one PC has audio at a time
External SSD / USB storage	Console USB port	Do NOT share this way — switching while a drive is mounted risks data corruption. Use a separate USB switch for storage.
Printer	Direct to new PC, or network printer	Network printer is accessible from both PCs without the KVM. Avoid USB-shared printers through the KVM.
Monitor 3 (165Hz)	Direct to new PC — never via KVM	Always shows new PC — no switching involved

Separate USB switch for shared storage: If you want a USB drive accessible from both PCs, use a dedicated USB switch (not the KVM) — a simple 2-port USB switch (~£8–15) with a physical button. This keeps storage switching independent from display/input switching. Always safely eject the drive on the current PC before pressing the USB switch button.

Hotkeys and Switching Methods

COMMON KVM SWITCHING METHODS Scroll Lock × 2 Most universal KVM hotkey ───────────────────────────────────────────────────────────── Press Scroll Lock (tap once) Press Scroll Lock (tap again within ~2 seconds) → KVM switches to next PC → Screen goes dark briefly (<1 second), then other PC's desktop appears Physical button on KVM Alternative if hotkey conflicts with software ───────────────────────────────────────────────────────────── Press the button on the front/top of the KVM unit Useful for gaming (Scroll Lock used in some games) Useful if keyboard doesn't have a Scroll Lock key Custom hotkey (brand-specific) ───────────────────────────────────────────────────────────── ATEN: Ctrl, Ctrl (can change to Caps Lock or Print Screen) TESmart: Ctrl+Alt+1/2 (switch to specific PC by number) Switch time: <1 second for display, near-instant for keyboard/mouse Audio (if via KVM 3.5mm): switches simultaneously with display

Remap the hotkey if Scroll Lock conflicts: Scroll Lock is used as a modifier in some terminal emulators, spreadsheet apps, and games. Most quality KVMs let you remap the trigger key via a firmware button combination (hold a button while pressing the new key). Check the manual — it's usually a simple sequence done once at setup.

Setup Verification Checklist

Monitor 3 running at 165Hz — confirmed before KVM setup: Display Settings on new PC shows 165Hz for the 2024 Samsung on its direct connection. This baseline is established before any KVM wiring begins.

Both 60Hz monitors detected by both PCs: Switch to each PC in turn. On the new PC, Monitors 1 and 2 appear in Display Settings at their correct resolutions (1920×1080 or 2560×1440) alongside Monitor 3. On the old PC, Monitors 1 and 2 appear at their correct resolutions.

EDID emulation confirmed — windows stay put: Open several windows on the new PC arranged across Monitors 1 and 2. Switch to the old PC. Switch back to the new PC. Every window should be exactly where you left it — same position, same size. If windows have moved to Monitor 3 or piled up, EDID emulation is not working.

Keyboard and mouse work on both PCs: After switching, open Notepad on each PC and type. Confirm the keyboard is routing to the correct machine. Move the mouse to confirm it's now controlling the newly active PC.

Switch time is acceptable (<2 seconds): Time the switch from button press to both monitors showing the other PC's desktop. Under 1 second is typical for modern KVMs at 1080p/60Hz. More than 3 seconds suggests a bandwidth or EDID handshake issue — check the cable quality (avoid no-name DisplayPort cables over 2m).

Hotkey works and doesn't conflict: Test Scroll Lock × 2 (or the KVM's hotkey) from within your typical working apps — VS Code, browser, terminal. If it conflicts with an application shortcut, remap the KVM hotkey or use the physical button instead.

Next: Type PC15 to generate Chapter 15 — Using a Multimeter for PC Diagnostics, covering the modes and settings you need, testing PSU voltages directly (independent of motherboard sensors), checking for shorts before first boot, diagnosing a completely dead component, and what the ATX voltage tolerances actually mean in practice.