Question Keyboard key presses are very delayed or entirely unresponsive

Troika

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Oct 17, 2014
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18,510
I have a Dell Precision M6800 that I've had for several years now and its given me very few issues to complain about. This one is by far the most annoying and I can't figure out what's causing it. Any time you press a key, its very slow to respond and typing at a regular pace doesn't yield several delayed keystrokes, often it just doesn't register any keystrokes at all. This behavior presists in bios as well.

Things I've already tried:
Reinstalling Windows 10
Trying a different OS (Win 7 & 11, Ububtu)
Replacing keyboard
Replacing motherboard
Replacing cpu
Replacing gpu (I happen to have other MXM cards just lying around)
Replacing/removing storage devices
Removing other add-on cards (WiFi module/Cellular Modem/etc)

I'm genuinely just stuck. Anyone else come across this issue before?

System Specs:
Intel i7 4910MQ (Undervolted with Throttlestop)
32GB DDR3-1600 Ram
AMD Radeon Pro WX 7100 Mobile 8GB (Modified vBios for lower power consumption and consisitent clock speed)
2TB Orico ZH-10 mSata
3x1TB Teamgroup T-Force Vulcan Z
Intel Wireless AC-7260
240w power adapter
 
Does this behavior occur when using an external keyboard?

Also, if you booted the system with a Live Linux distro (from a USB drive, you don't need to install it) does the behavior happen then?

Intent is to isolate whether a hardware or software issue.
No, when using an external keyboard (usb or bluetooth) it functions normally.

And yes, the behavior is present when using a portable OS. I have a Windows live image as well as a Ubuntu one, both have the same issue when using the laptop's keyboard. As I stated, the behavior is also present when interacting with bios so it shouldn't be a driver related issue.
 
I agree, you have a hardware issue. When you replaced the keyboard, did that include the ribbon cables to attach to the motherboard as well?
Yes, I even replaced the cable with a new one incase there was an internal break that wasn't obviously visible. I took everything out of the laptop other than a single stick of ram and removing the gpu and all other expansion cards. The same issue still persists. I genuinely have no clue what could possibly be causing this. The only thing I haven't replaced at this point is the display panel and I REALLY rather not do that.

I'm just gonna shelve my Dell Precision and swap over to a old Clevo laptop that I picked up last year.
 
I am leaning toward the motherboard being the problem, the part where it connects the keyboard to it. You have ruled out pretty much everything else.

You mentioned replacing the motherboard and keyboard before. One, or both, could have an issue. From where did you source the parts?
 
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