Dell 2560*1440 60hz external monitor , trackpad is lagging

Hi there ertom63,

If you are experiencing a delay when using a Magic Trackpad with your MacBook Pro, we'd firstly like to gather some more information so that we can start to isolate this issue.

To start, does this occur only when the MacBook Pro is connected to this external monitor or even when it is disconnected? Does this happen when the Magic Trackpad is connected via Bluetooth, hard wired to your Mac, or both?

Adjusting the Trackpad settings can also resolve issues like this. This article walks you through how to do this and what can be adjusted: Change Trackpad settings on Mac

Also, ensure your Mac is fully updated. This installs feature improvements and fixes that can alleviate issues like this. These steps from Update macOS on Mac show how to back up and update:

Before installing new software, it's a good idea to back up your Mac.

To check for new software, open Software Update. It's in System Settings (or System Preferences), which you can open from the Apple menu  in the corner of your screen:

* Choose Apple menu  > System Settings. Click General on the left side of the System Settings window, then click Software Update on the right.

* Or choose Apple menu  > System Preferences, then click Software Update.

If Software Update finds new software, click the button to install it, then enter your administrator password when prompted. During installation, your Mac might show a progress bar or blank screen several times, and you should avoid putting it to sleep or closing its lid.

Cheers!

There are two unrelated issues that can make the pointer lag.

one is WiFi/Bluetooth interference.

Why do I have difficulty with Wi-Fi or Bluetooth devices when USB 3 devices are attached to my computer?

Some USB 3 devices can generate radio frequency interference that can cause Wi-Fi and Bluetooth devices operating in the 2.4GHz band to have issues communicating with your computer. Here are some tips to avoid this issue:

• If your USB device has a cable long enough that you can move the device, place it away from your Mac—and make sure not to place it behind your Mac, or near the hinge of its display. The antennas for Wi-Fi and Bluetooth are located there, and USB 3 devices placed there might interfere with your wireless connections.

• If you're using adapters or dongles on a Mac computer with Thunderbolt 3 (USB-C) ports, plug them into the front port on the left side of your Mac, or into the ports on the right side (if your computer has them). These ports are the farthest away from the antennas, making interference less likely.

• To avoid interference on the 2.4GHz band using Wi-Fi, try using the 5GHz band instead. You can change this on your wireless base station. Bluetooth always uses 2.4GHz, so this alternative isn't available for Bluetooth.

from:

About USB on Mac computers - Apple Support

Resolve Wi-Fi and Bluetooth issues caused by wireless interference

Resolve Wi-Fi and Bluetooth issues caused by wireless interference - Apple Support

cursor-position updating is done at low priority in the background. if your Mac is excessively busy doing other things, cursor position update could lag. things like protein folding simulations, video editing, or other intensive processes can cause lag.

By far the easiest way to cause cursor lag, instability, and crashing is to install ANY third-party speeder-uppers, Cleaners, Optimizers, or Virus scanners. or a VPN that you installed yourself.

The idea that a third party, with no special knowledge of the inner workings of MacOS, can somehow find a simple way to protect your computer — that is not already being done by MacOS itself — suggests that the MacOS developers are somehow "holding out on you". That is absurd.

You should remove any and all (other than Apple built-in) virus scanners, speeder uppers, optimizers, cleaners, App deleters or VPN packages you installed yourself, or anything of that ilk.

Third-party file Sync-ers such as DropBox, BackBlaze, OneDrive, or GoogleDrive can ruin performance, but are not inherently dangerous.

refreshing the screen is a very intensive process, and requires a lot of hardware activity at high speed with very tight timing. But almost NONE of that activity takes any processor resources to accomplish. when the processor is late, the screen with either flash or go completely blank, and nothing else will work either, at least for a moment. you are barking up the wrong tree.

Got any third-party anti-virus running?

got any DropBox or other third-party file-syncers running?

<< when im trying to using the trackpad directly on the macbook pro , it works smoothly >>

¿ how else were you connecting it other than wired and directly to your Mac?

¿ so does this mean your problem is solved?

so wired directly to a port on the MacBook Pro chassis works.

wired to a USB port on the display lags?

wireless lags?

are you connecting the display with a USB cable 1 meter or shorter?

are you using Wi-Fi for your Internet connection? 2.4GHz or 5 GHz band?

any other peripherals in use?