GPU Connected to TV: No 4K 120Hz, Cropped Picture or Blurry Text? HDMI 2.1 Bandwidth, 4:4:4 Chroma, Overscan & Game Mode Explained

2026-10-23 ｜ GPU Repair ｜ About 24 minutes ｜ HK GPU Fix Editorial Team

Summary

Connecting a graphics card to a television can hide four different problems behind one blurry or cropped picture: limited HDMI bandwidth, missing 4:4:4 chroma support, television overscan, and extra image processing. This guide explains each cause, how to check port by port, and which settings to change first.

Why a Television Is Not Simply a Large Monitor

A television and a computer monitor both accept an HDMI signal and show a picture, but they are built for different jobs, and that difference explains most GPU-to-TV problems. A monitor is designed to show a computer signal with as little alteration as possible: each pixel from the graphics card maps to a pixel on the panel, and text stays sharp because nothing in between resamples or smooths it. A television is designed to make broadcast and streaming video look pleasing from a sofa: it sharpens, smooths, adjusts colour, and sometimes crops or scales the picture, because video content tolerates those changes and often benefits from them.

When a graphics card is connected to a television, the computer signal passes through that television pipeline. If the pipeline is left in its video mode, a desktop that would be crisp on a monitor can look soft, cropped, or oddly coloured on a television, even though the graphics card, the cable, and the television are all functioning. The fix is therefore rarely a single setting. It is a chain: enough HDMI bandwidth for the chosen resolution and refresh rate, the right chroma format for sharp text, a one-to-one pixel mapping without overscan, and a television mode that bypasses video processing. A break anywhere in that chain shows up as a picture problem, and the symptom points back to which link broke.

HDMI Bandwidth: Why 4K 120Hz Needs More Than a 4K Label

HDMI bandwidth is the amount of signal data the connection can carry per second, and it sets a hard ceiling on which combinations of resolution, refresh rate, colour depth, and chroma format are possible. A connection that is adequate for 4K at 60Hz may not be adequate for 4K at 120Hz, and a connection that carries video cleanly at a compressed chroma format may fail or fall back when full chroma is requested. The television, the graphics card, the cable, and the specific port in use must all support the same bandwidth; the chain runs at the capability of its weakest link.

The two HDMI generations most relevant here are HDMI 2.0 and HDMI 2.1. HDMI 2.0 supports up to 18 gigabits per second of video bandwidth, which covers 4K at 60Hz with standard colour settings, but not 4K at 120Hz at full quality. HDMI 2.1 supports up to 48 gigabits per second, which covers 4K at 120Hz, and higher combinations that also depend on the television panel and the graphics card. Those figures describe the interface ceiling, not a promise: a television marketed with an HDMI 2.1 label may still implement the full bandwidth on only some of its ports, and a cable marketed for 4K may predate the higher bandwidth standard entirely.

That distinction drives the first diagnostic rule for any missing 4K 120Hz option. Do not ask whether the television "has HDMI 2.1" as a single yes-or-no question. Check port by port. Some individual HDMI 2.1 ports in fact provide only 40 Gbps rather than the full 48 Gbps, so check the model specification table rather than assuming every 2.1 port is identical. The enhanced format also has to be enabled in the television settings, under brand-specific names such as Samsung Input Signal Plus (formerly HDMI UHD Color), Sony Enhanced format (on some models Enhanced format (4K120, 8K)) and Hisense HDMI Format set to Enhanced format. Television HDMI ports may differ in version and capability, and the correct question is which individual port, with which cable, is carrying the signal. The port labels on the back of the set, the television's input information display, and the graphics card control panel's reported link capability together answer that question; a general specification page for the television model does not, because it may describe the best port rather than the port actually in use.

Display stream compression, often shortened to DSC, complicates the picture further. DSC compresses the signal in a visually lossless way so that a combination that exceeds the raw bandwidth can still be carried. Some televisions and graphics cards use it, some do not, and its availability depends on the exact port, cable, and driver combination. A missing 4K 120Hz option therefore does not automatically mean any single component is faulty; it may mean DSC is unavailable on that port, or that the television panel itself does not accept 120Hz input at 4K even though its panel refreshes at a higher rate for motion processing. Panel motion rate figures marketed for video smoothing are not the same as the input refresh rate the HDMI port accepts, and confusing the two is a common source of disappointment.

Cables: The Invisible Bottleneck

The cable is the easiest link to overlook and one of the first causes worth checking for a missing high refresh rate. An older HDMI cable, or a long cable run through a wall or an adapter, may carry 4K at 60Hz reliably while failing at 4K at 120Hz, or it may cause intermittent dropouts, flicker, or a fallback to a lower refresh rate that looks like a graphics card problem. Cable length matters because signal quality degrades with distance, and the margin that is comfortable at lower bandwidth disappears at higher bandwidth.

For HDMI 2.1 bandwidth, the relevant cable category is Ultra High Speed HDMI, which is certified for the full 48 gigabits per second. A cable that merely says "4K" or "high speed" on its packaging may belong to an earlier category that was certified for lower bandwidth, and a cable bought years ago for a 1080p setup should not be assumed adequate for 4K 120Hz. During diagnosis, test with a short, certified Ultra High Speed cable connected directly between the graphics card and the television, with no adapters, wall plates, switches, or soundbar pass-through in between. If the higher refresh rate appears with the direct cable and disappears when the original run is restored, the original run, not the graphics card or the television, was the limiting link. Adapters and pass-through devices should be reintroduced one at a time after that, so any device that reduces bandwidth is identified rather than assumed.

Cable direction also deserves a brief note. Most passive HDMI cables work in either direction, but active cables and long optical HDMI cables can be directional, with a source end and a display end marked on the connectors. A directional cable connected backwards may show no picture at all, or a picture at a reduced capability. Checking the markings during a cable swap prevents a working cable from being mistaken for a faulty one.

Chroma Subsampling: Why Video Looks Fine but Text Looks Blurry

Chroma subsampling is the reason a television picture can look excellent for video while text on the same screen looks fringed, smeared, or hard to read. Human vision is more sensitive to brightness detail than to colour detail, so video systems often store full brightness information for every pixel but share colour information across groups of pixels. That sharing is described by a three-number notation: 4:4:4 means full colour information for every pixel, 4:2:2 means colour information shared horizontally across pairs of pixels, and 4:2:0 means colour information shared across a block of pixels in both directions.

For video, subsampling is usually invisible, because moving pictures and natural gradients hide the shared colour. For computer text, it is highly visible, because a sharp letter edge depends on a sudden colour change at a single pixel boundary. With 4:2:2 or 4:2:0, that edge is averaged across neighbouring pixels, so coloured text, especially small red, blue, or green text on a contrasting background, looks blurred or fringed even though the resolution setting claims 4K. Black text on a white background survives subsampling better than coloured text, which is why a desktop can look "almost sharp" while coloured interface elements and small fonts look wrong.

Television support for 4:4:4 at 4K varies by model, by port, and by input mode. Many televisions only offer full chroma when the input is set to PC mode or a similarly named computer mode, and only on certain ports. The graphics card control panel usually reports the current chroma format, or the output colour format, and that report is the ground truth for what the chain is actually delivering, regardless of what the television marketing claims. If the control panel reports 4:2:0 or 4:2:2 while the desktop text looks blurry, the diagnostic direction is clear: find the television input mode and port combination that permits 4:4:4 at the chosen resolution and refresh rate, and accept that the combination may require a bandwidth compromise, such as a lower refresh rate, on a port that cannot carry full chroma at 120Hz.

Colour format interacts with chroma. RGB output carries full colour information in a form computers use directly, while YCbCr output separates brightness from colour and is the native form for video. Some televisions handle one format better than the other at a given resolution, and some graphics drivers default to a YCbCr mode on a television that would be better served by RGB. The output dynamic range must also match on both sides: full-range RGB uses 0–255 while limited range uses 16–235, so a mismatch can wash blacks out to grey or crush dark detail. If text remains blurry after 4:4:4 is confirmed, testing the alternative output colour format, with a single change and a retest, is a reasonable next step, provided the change is recorded so it can be reversed.

Overscan: Why the Edges Disappear

Overscan is a legacy television behaviour that crops the edges of the picture. It originated with analogue broadcast, where the edges of the frame could contain noise or timing artefacts, so televisions deliberately enlarged the picture slightly and cut off the border. Modern digital signals do not need that treatment, but many televisions still apply overscan by default on HDMI inputs, because their default mode assumes a video source.

On a computer desktop, overscan is immediately obvious: the taskbar is cut off at the bottom, window edges disappear on the sides, and the mouse pointer seems to vanish at the screen edge. The graphics card is sending a complete frame; the television is discarding its border. The fix sits on the television, not in the graphics card's resolution setting. Look for a picture size or aspect setting named Just Scan, Screen Fit, Full Pixel, 1:1 Pixel Mapping, or Dot by Dot, depending on the television brand, and select it. Equally important, avoid the graphics card's own overscan or underscan compensation slider as a permanent fix: that slider rescales the desktop to fit inside the cropped area, which restores visibility at the cost of a resampled, slightly soft picture, and it masks the television setting that should have been corrected.

Some televisions apply overscan only in certain modes, or only on certain inputs, which is another reason to check port by port and mode by mode rather than assuming a single television-wide setting. A port configured as a PC input may already disable overscan, while a neighbouring port configured as a video input crops the same signal. If the edges disappear on one port and not another, with the same cable and the same graphics card settings, the difference is in the television's per-input configuration, and copying the working input's settings to the other input is the correct remedy.

Game Mode, PC Mode, and the Processing Pipeline

Game Mode and PC Mode are television modes that reduce or bypass the video processing pipeline, and understanding what each bypasses explains both their benefits and their trade-offs. In standard video mode, the television may apply noise reduction, motion smoothing, edge enhancement, dynamic contrast, and colour adjustments, each of which adds delay and alters the picture. For broadcast video, that processing is often welcome. For a computer desktop or a game, it adds input lag, softens text, and can introduce motion artefacts around the mouse pointer and fast-moving objects.

Game Mode primarily targets input lag: it disables most processing so that a controller input or mouse movement appears on screen sooner. PC Mode, where a television offers it, targets computer signal fidelity: it enables full chroma support, disables overscan, and reduces processing, so the desktop maps pixel for pixel. On many televisions the two overlap, and on some the correct setting is a combination: renaming or labelling the input as PC, then enabling Game Mode for that input. On others, the modes are separate and choosing one disables the benefits of the other, so the television manual for the specific model is worth consulting rather than assuming a mode name means the same thing across brands.

Input labelling matters more than it appears to. Some televisions only unlock PC Mode, full chroma, or full bandwidth on an input that has been labelled or configured as a computer input, even if the same port carries the same signal under a generic label. Renaming the input to PC, or selecting a PC icon for it, is therefore a real configuration step, not cosmetic tidying. Similarly, Auto Low Latency Mode, where supported, lets the console or graphics card signal the television to switch into its low-latency mode automatically when a game starts, and back when video playback resumes; if that handshake fails on a particular port, the television may stay in video mode for games and the symptom will look like unexplained lag.

Resolution, Refresh Rate, and Scaling: Setting the Chain in the Right Order

The order in which settings are changed matters, because a later setting can silently override an earlier one. Start from the graphics card control panel or the operating system display settings, and confirm the basics before touching advanced options: the resolution matches the television panel's native resolution, the refresh rate is one the port and cable actually support, and the display is not set to duplicate another monitor at a lower common resolution. Duplication forces all duplicated displays to a resolution and refresh rate they share, which often means the television is held below its capability by a second monitor, and the fix is to extend the desktop instead of duplicating it, or to test with the television as the only display.

Windows display scaling interacts with television sharpness in a subtler way. At 4K on a large television viewed from a sofa, a scaling setting above the default enlarges text and interface elements for readability, which is legitimate, but it also means the desktop is rendered and then scaled, so text will not look as pixel-sharp as unscaled output on a monitor at desk distance. That is a viewing-distance trade-off, not a fault, and it should not be confused with chroma blur: scaling blur affects all text uniformly and improves with a larger scaling choice or a closer viewing position, while chroma blur fringes coloured edges specifically and persists regardless of scaling. The graphics card's own scaling setting should generally be left off for a television connection, so scaling happens in one place only, rather than being applied twice.

Television sharpness and picture presets also belong on the checklist. A high sharpness setting on a television adds artificial edge enhancement that can make computer text look harsh, haloed, or noisy, while a very low sharpness setting can look soft. In PC or Game Mode, sharpness is usually neutralised, which is another reason those modes matter for computer use. If the desktop looks acceptable in PC Mode but harsh or soft in standard mode, the difference is the television preset, not the graphics card output, and the remedy is to stay in the computer mode for computer use.

HDR, Colour Depth, and the Bandwidth Trade-Off

High dynamic range, or HDR, increases the bandwidth demand of the same resolution and refresh rate, because it carries more brightness and colour information per pixel. A chain that carries 4K at 120Hz without HDR may not carry the same combination with HDR enabled, and the result is often a silent fallback: the system drops to a lower refresh rate, a subsampled chroma format, or a lower colour depth, without an explicit warning. Checking whether HDR is enabled, and whether the fallback disappears when HDR is disabled, separates an HDR bandwidth limit from a general port or cable limit.

Colour depth works the same way. Standard output uses 8 bits per colour channel, while higher depth output uses 10 or 12 bits per channel and demands more bandwidth. For desktop use, higher colour depth offers little visible benefit over standard depth on most content, and forcing it can cost a refresh rate or a chroma step that matters far more for text clarity. The practical priority for a computer connection is usually refresh rate and full chroma first, HDR and higher colour depth second, unless the primary use is HDR video playback, in which case the priority reverses and the refresh rate compromise is accepted knowingly.

Windows HDR settings, graphics driver colour settings, and television HDR handling must also agree. If HDR is enabled in Windows but the television input is not in an HDR-capable mode, or if the television expects an HDR signal on one port but not another, the picture may look washed out, overly dark, or incorrectly coloured. Testing with HDR disabled, confirming a clean standard picture first, and then re-enabling HDR on the confirmed working port and mode is a more reliable sequence than enabling everything at once and trying to interpret a combined failure.

EDID: How the Television Tells the Graphics Card What It Supports

When a television and a graphics card connect, the television reports its supported resolutions, refresh rates and colour capabilities through EDID (Extended Display Identification Data), and the graphics card offers only the combinations that report describes. The problem is that an AV receiver, splitter, adapter or older cable in between can rewrite, truncate or substitute that report, so the graphics card concludes the television supports only a lower specification and the 4K 120Hz option simply disappears. That can look like a faulty graphics card or television when it is really the intermediate device rewriting the capability report. A direct connection is the test that isolates this: if 4K 120Hz appears when connected directly and vanishes through the intermediate device, the intermediate device is the cause, and it should be reintroduced one piece at a time rather than blamed on the graphics card.

A Diagnostic Sequence for GPU-to-TV Problems

The sequence below works through the chain from the cheapest and most easily checked causes to the more specific ones, changing one thing at a time.

Record the working combination once it is found: port number, cable type, television mode and input label, resolution, refresh rate, chroma format, and HDR state. Television firmware updates, graphics driver updates, and even unplugging the set can reset per-input settings, and a written record turns a future recurrence into a five-minute restoration instead of a fresh investigation.

Common Misconceptions Worth Clearing Up

The first misconception is that a television's advertised panel refresh rate guarantees the same input refresh rate. Panel motion processing can refresh the panel faster than the HDMI input accepts, by interpolating frames internally. A television marketed with a high motion rate may still accept only 60Hz input at 4K on its HDMI ports, and no cable or graphics card setting can exceed the input limit. The input specification, not the motion marketing figure, is the number that matters for a computer connection.

The second misconception is that a higher resolution always looks sharper on a television. If the chain cannot carry that resolution at full chroma, or if the television scales a non-native resolution, a lower resolution at full chroma and one-to-one mapping can look sharper for text than a higher resolution delivered subsampled or rescaled. Sharpness for computer use is a product of resolution, chroma, mapping, and processing together, not of resolution alone.

The third misconception is that a blurry television picture means the graphics card is weak or faulty. A graphics card that drives a monitor crisply at the same resolution is demonstrating that its output is sound; the difference on the television is in the television pipeline, the port, or the cable. Swapping the graphics card before checking the port, the mode, and the chroma format wastes effort and can lead to an unnecessary replacement.

The fourth misconception is that all HDMI ports on one television are identical. They are not necessarily identical, and this guide returns to the point because it causes more wasted diagnosis than any other single assumption: television HDMI ports may differ in version and capability, so check port by port, with the same cable, and record which port delivers which combination.

When to Seek Inspection

Most GPU-to-TV problems resolve through the sequence above, because they are configuration and chain problems rather than faults. Seek inspection when the pattern points beyond configuration: the same graphics card and cable drive a monitor correctly but no television port, mode, or cable produces a stable picture; the picture drops out, flickers, or shows artefacts on every port and cable, including at low resolutions; the television input itself is physically damaged; or the graphics card output is unstable on both a monitor and a television after driver and cable checks. In those cases the fault may sit in the graphics card output, the television input board, or the connection between them, and further testing at home risks confusing two separate faults.

For inspection of the graphics card side, HK GPU Fix operates a shop at Dali Plaza, Shek Mun. The shop telephone is 2186 8010 and WhatsApp is 6558 6806. Repair pricing follows the site's published three-tier range of HK$400 to HK$2,800. No door-to-door service is offered, and there is no Mong Kok shop, so any visit is to the Shek Mun shop. Bringing the recorded working and non-working combinations, including port numbers, cable type, and television mode settings, will help inspection distinguish a card fault from a chain or television configuration issue.

A Pre-Connection Checklist for the Next Television Setup

Before connecting a graphics card to a new television, five checks prevent most of the problems described in this guide. Confirm which individual port supports the desired resolution and refresh rate, rather than relying on a general model specification. Use a short, certified Ultra High Speed cable for the initial test, connected directly with no adapters. Set the television input to PC Mode where available, enable Game Mode for that input, and select the one-to-one picture size setting. Confirm full chroma output in the graphics card control panel before judging text sharpness. Finally, settle refresh rate and chroma before enabling HDR or higher colour depth, so any bandwidth compromise is a conscious choice rather than a silent fallback. A connection set up in that order starts sharp, uncropped, and at the refresh rate the chain truly supports.

Frequently Asked Questions

Why does my television not offer 4K 120Hz when the box says HDMI 2.1?

Because HDMI capability can vary by port. Some televisions provide full HDMI 2.1 bandwidth on only one or two ports, while other ports run at a lower capability. Check port by port with the same cable, and use the port that actually offers the combination. The cable must also be a certified Ultra High Speed cable, and the panel must accept 120Hz input at 4K, which is separate from a motion processing figure.

Why is video sharp but computer text blurry on the same television?

Because video tolerates chroma subsampling while text does not. If the chain is delivering 4:2:2 or 4:2:0, colour information is shared across pixels, which moving video hides but sharp letter edges reveal. Confirm 4:4:4 output in the graphics card control panel, and set the television input to PC Mode where available, since many televisions only permit full chroma in that mode.

Why are the edges of my desktop cut off on the television?

Because the television is applying overscan, a legacy behaviour that enlarges the picture and discards its border. Select the one-to-one picture size setting, such as Just Scan, Screen Fit, Full Pixel, or Dot by Dot, depending on the brand. Avoid using the graphics card's overscan compensation slider as a permanent fix, since it rescales the desktop and softens the picture.

What is the difference between Game Mode and PC Mode?

Game Mode mainly reduces input lag by bypassing video processing. PC Mode mainly improves computer signal fidelity by enabling full chroma, disabling overscan, and reducing processing. On many televisions the best computer setup combines both: a PC-labelled input with Game Mode enabled for that input. The exact behaviour varies by brand and model, so the television manual for the specific model is the final reference.

Should I buy a new cable before changing any settings?

Test first with the cable you have, on the correct port and in the correct television mode, before concluding the cable is at fault. If a short, certified Ultra High Speed cable connected directly restores a missing refresh rate that a longer or older cable cannot carry, the cable run was the limit. Reintroduce adapters and pass-through devices one at a time afterwards, so any device that reduces bandwidth is identified.

Does HDR make the desktop look worse on a television?

HDR itself does not make a desktop worse, but enabling it raises bandwidth demand, which can force a silent fallback to a lower refresh rate, subsampled chroma, or lower colour depth. If text clarity or refresh rate degrades when HDR is enabled, test with HDR disabled to confirm the trade-off, then decide whether HDR video or desktop sharpness is the priority for that input.

Why does duplicating my monitor to the television lower the television resolution?

Because duplication forces all duplicated displays to a shared resolution and refresh rate. If the monitor cannot match the television, the television is held to the common capability. Extend the desktop instead of duplicating it, or test with the television as the only display, to see the television's true capability.

My television picture looks fine, but games feel delayed. What should I check?

Check Game Mode first, since standard video processing adds delay between input and display. Confirm the input is in Game Mode, check whether Auto Low Latency Mode is engaging for that input, and confirm the refresh rate is actually running at the expected value rather than falling back to a lower rate. A high refresh rate in a menu does not guarantee the same rate is sustained in gameplay if the chain falls back under load.