Reply to thread

Message: [QUOTE="Bombastus, post: 91472, member: 2178"] Intel specifies support for two 4K 60 Hz displays through one Thunderbolt 4 port when you use a compatible dock. Running both at 120 Hz asks more of the setup. Compatible hardware can do it, so 60 Hz isn't an absolute ceiling. You still need confirmation for two screens operating together, not a specification that describes either screen on its own. A working picture proves very little about the remaining capacity. [HEADING=2]Your laptop can halve the promised refresh rate[/HEADING] Plugable's UD-4VPD supports two 4K 120 Hz displays on compatible Windows 11 computers with USB4 or Thunderbolt 4. Its requirements include DisplayPort 1.4 with HBR3 signaling and Display Stream Compression, usually shortened to DSC. DSC reduces the video data needed for a given display mode. The computer must support the dock's required combination of features, rather than merely have a socket with the right logo. Plugable warns that not every USB4 or Thunderbolt 4 computer qualifies. Its compatibility table names an HP EliteBook 845 G9 configuration that supports one 4K display at 120 Hz but two at 60 Hz. The listed machine uses a Ryzen Pro 6650U processor. Those results reference an August 2023 driver configuration, not every possible software revision of that laptop. Treat them as a documented exception, not proof of a permanent hardware limit. The single-screen result still cannot establish dual-screen performance. For a purchase decision, ask for [B]two independently usable 4K screens at 120 Hz[/B] on your exact laptop model and intended dock. Include the graphics configuration and operating system, rather than accepting a reply that simply repeats the dock's maximum resolution. [HEADING=2]The second output needs the right connection[/HEADING] The [B][URL='https://goldmidi.com/community/threads/lenovo-started-selling-thinkvision-p27ud-40-in-china.76846/']ThinkVision P27UD-40's separate video outputs[/URL][/B] include Thunderbolt 4 and DisplayPort 1.4. Their presence gives you different connection options, not a confirmed dual-screen refresh rate. Lenovo's port list alone doesn't settle what your laptop can deliver through them. DisplayPort daisy-chaining uses Multi-Stream Transport, or MST, to carry multiple displays over one connection. Windows supports independent desktops through compatible MST setups, while macOS does not support that same extended-desktop arrangement. A Mac can support independent screens through a suitable Thunderbolt connection, subject to its own display limits. Ordinary DisplayPort daisy-chaining is not an equivalent substitute. You need to distinguish the connection carrying the second picture, not just the cable entering the first monitor. Plugable's dock illustrates the difference. On the Macs covered by its compatibility guidance, connecting both HDMI outputs produces mirrored pictures rather than two separate workspaces. Only one external display appears in macOS display settings. Two illuminated panels therefore aren't enough to verify the setup. Open different windows on each screen and check that you can move one without changing the other, then inspect both refresh rates. A seller's demonstration should show the complete connection you intend to use. Two monitors connected separately to a laptop don't establish that a single dock connection can drive them at the same settings. Different test, different evidence. [HEADING=2]A 120 Hz reading can hide another compromise[/HEADING] Refresh rate also leaves out features you might expect to keep. Plugable explicitly excludes HDR and adaptive sync support on the UD-4VPD, despite advertising dual 4K 120 Hz operation. You can meet the resolution and refresh-rate target without meeting your full requirements. Neither an HDR-capable panel nor its adaptive refresh specification overrides the dock's limitations. Check those features separately instead of treating 120 Hz as proof that everything works. Test each monitor separately through its intended dock output at 3840 by 2160 and 120 Hz before connecting both. A failure with only one attached means the problem already exists without the second screen, so troubleshoot that connection first. For a Windows test, leave both monitors connected and use an extended desktop. Open Settings, System, Display, then Advanced display, and select each external monitor in turn. Record the resolution and refresh rate shown for each screen before changing anything. Select 120 Hz where available, then inspect both displays again. Checking only the monitor you just adjusted leaves the other one's settings unverified. Windows places an asterisk beside refresh rates that don't support the current resolution. Selecting one of those entries changes the resolution to achieve the chosen rate, so the higher number comes with a change elsewhere. A screen running at 120 Hz after dropping from 3840 to 2160 hasn't passed a 4K test. Both monitors need to retain that resolution and refresh rate at the same time. Otherwise, you've verified a different display mode from the one you planned to buy. [/QUOTE]

Name