[Power/EMI] I discover why sometime PC become fast and low input lag and otherwise feel high input lag

[alexander1986]

hm, damn ... that is interesting and worrying at the same time @KingJosh2475 and @nuggify ..


I can easily see consoles like xboxes and playstations being affected by EMI problems since they have to be connected to power, so in Josh's case I guess I got my answer, but as for you nuggify and the phenomenon even occuring on a laptop on battery that is disturbing imo,

since it would kind of indicate extreme (?) levels of radiated EMI in the air even, that sounds like a potential health hazard even ?


its honestly frustrating too that this problem even exists and that companies like power providers and so on are most likely completely oblivious to the fact, " as long as the power works, it works " is kind of what I assume their stance would be on it ...

imagine also moving in to a apartment or house where the issue exists and you are a gamer, competitive or not, and having to deal with this BS, without knowing this phenomenon exists, I wonder how many gamers out there in the world suffer in silence of this or just have no idea that this could be a cause of it...

:/

[Unixko]

hm, damn ... that is interesting and worrying at the same time @KingJosh2475 and @nuggify ..


I can easily see consoles like xboxes and playstations being affected by EMI problems since they have to be connected to power, so in Josh's case I guess I got my answer, but as for you nuggify and the phenomenon even occuring on a laptop on battery that is disturbing imo,

since it would kind of indicate extreme (?) levels of radiated EMI in the air even, that sounds like a potential health hazard even ?


its honestly frustrating too that this problem even exists and that companies like power providers and so on are most likely completely oblivious to the fact, " as long as the power works, it works " is kind of what I assume their stance would be on it ...

imagine also moving in to a apartment or house where the issue exists and you are a gamer, competitive or not, and having to deal with this BS, without knowing this phenomenon exists, I wonder how many gamers out there in the world suffer in silence of this or just have no idea that this could be a cause of it...

:/

so many brother so many

[howiec]

hm, damn ... that is interesting and worrying at the same time @KingJosh2475 and @nuggify ..
I can easily see consoles like xboxes and playstations being affected by EMI problems since they have to be connected to power, so in Josh's case I guess I got my answer, but as for you nuggify and the phenomenon even occuring on a laptop on battery that is disturbing imo,
since it would kind of indicate extreme (?) levels of radiated EMI in the air even, that sounds like a potential health hazard even ?
its honestly frustrating too that this problem even exists and that companies like power providers and so on are most likely completely oblivious to the fact, " as long as the power works, it works " is kind of what I assume their stance would be on it ...
imagine also moving in to a apartment or house where the issue exists and you are a gamer, competitive or not, and having to deal with this BS, without knowing this phenomenon exists, I wonder how many gamers out there in the world suffer in silence of this or just have no idea that this could be a cause of it... :/

so many brother so many

I'm sure someone else has said this before but as an electrical engineer, I can tell you that EMI should have zero effect on your "input lag" UNLESS you're talking about wireless networking or peripherals (e.g. mouse & keyboard).

Electrical circuits from a data signal perspective always take noise and EMI into consideration (if well-designed). Your PC parts have EMI protection circuitry and components and designers follow basic circuit design rules to ensure that things work as intended and that data signals are clean enough.
If signals were suffering from significant interference, then you'd most likely see erratic behavior or ultimately crashes, not a delayed reaction such as input lag.

As for power going into your PC, it's always worth buying a good power supply. It's job is to ensure "clean" DC power output and protect/mitigate various failure modes. If you have a bad one, usually the failure isn't simply input lag, it's usually freezing/crashing, inability to power on, or catastrophic failure such as shorting and overheating.

Power supplies aren't that susceptible to EMI if designed correctly. On the contrary, power supplies are a likely source of EMI if not designed correctly. They need to pass various EMC regulatory testing standards, e.g. FCC, CISPR, IEC.

[Chief Blur Buster]

I'm sure someone else has said this before but as an electrical engineer, I can tell you that EMI should have zero effect on your "input lag" UNLESS you're talking about wireless networking or peripherals (e.g. mouse & keyboard).

Part 1 of 2

Actually, it's rare but it has happened. I am crossposting something else I wrote on another forum at ArsTechnica:
____________

Interference problems can create really WEIRD effects for a lot of modern gadgets. When interference is strong enough -- and/or the shielding is weak enough.

Like the LG 5K display that glitched if a WiFi router was nearby.

I've also gotten anecdotes from spectrum-analyzer using engineers/techs where they found weird videogaming sutters/glitches caused by electricity noise.

The interference was nearly (but not quite) strong enough to crash a computer. Instead, the computer was severely slowing/lagging from apparent error correcting behaviours.

We don't know what specific slowdowns were caused by -- flood of IRQ interrupt noise or error-correcting behaviours on SATA cables or noise on ECC DRAM buses or some other mysterious EMI-based slowdown effects, or a PCI Express bus trying to retransmit data during noise errors -- probably error correcting by the millions, like death by a million nanoseconds or microseconds that added up to continually visible slowdowns (game stutter, Window-dragging stutter, scrolling stutter, etc). Even when nothing was running in background (CPU/GPU near 0%), and scanners found no viruses.

Like thousands of microfreezes per minute.

The computer really performed erratically slow in a way that wasn't blameable on Microsoft Windows in particular as patterns persisted regardless of what was installed or reinstalled. And it was only when the interference was occuring. When the culprit appliance was removed, the computer went back to full speed. The engineer's testing equipment confirmed massive interference noise was somehow being injected into the computer that slowed down / stuttered everytime the noise occured. The massive amounts of error correction layers that portions of a modern computer has, apparently prevents the computer from crashing.

It's possible some components were suboptimal/defective or it was a cheap motherboard, or a poorly EMI-rejecting computer power supply. But at some point, some forms of interference can become too strong for a hardened computer to resist fully. And they apparently don't always crash right away thanks to all those error-correcting buses (PCI, SATA, NVMe, ECC RAM, USB, LAN, DisplayPort, etc, all of which use error correction now). It can be bad enough like an Internet connection losing 50% of its packets, but on a PCI Express bus, or USB cable, or NVMe SSD or whatever -- things really slow down there too if interference is strong enough but still lets enough data through that the computer doesn't crash.

All the numerous error correcting buses found in modern PCs, that didn't exist 25+ years ago. Error correction behaviours often involve latency, including bandwidth reductions or retransmission latency or extra wait states or ultrabrief computer freezes, etc. We don't know which error correcting layer occured, but we know computer reliably sped up/slowed down everytime the known electrical interference was added/removed.

Usually error corrections in a PC on these layers are nanoseconds or microseconds but they can apparently daisychain by the thousands into visible milti-millisecond microfreezes covering multiple display refresh cycles! Which just appears as stutter (choppy motion on a screen). It's hard to diagnose exact causes of specific stutters (from driver bugs or thermal throttling or background processing).

But apparently, this computer slowdown was EMI-caused -- visible stutter from electricity noise coming from the power outlet!

There's a ton of weakly-shielded cheap electronics or even shielding-defective high end electronics. And time can degrade many device like these TVs degrading into unintentional small-scale EMPs.

Very weird!
_____
--end of crosspost; begin of reply--

WARNING / CAVEAT: This is usually a wild goose to a red herring more than 99% of the time. However, it's not out of the realm of possibility for strong-enough EMI to start "thousand-microfreezes" lagging an insufficiently-shielded PC. The type of "EMI strength + shielding weakness" combo that is strong enough to almost, but not quite, crash a PC. I've seen at least a few examples in the last few years. TL;DR: EMI can cause computer lag as described, BUT it's very rare. It definitely ain't a five-sigma "No", just rare. Unless you have the time and absolutey exhausted other avenues, do not waste time troubleshooting longshots; troubleshoot the low-lying apples first!

[Chief Blur Buster]

As for power going into your PC, it's always worth buying a good power supply. It's job is to ensure "clean" DC power output and protect/mitigate various failure modes. If you have a bad one, usually the failure isn't simply input lag, it's usually freezing/crashing, inability to power on, or catastrophic failure such as shorting and overheating.

Part 2 of 2

Also, read the Milliseconds Matter Thread: The Amazing Human Visible Feats Of The Millisecond, where some milliseconds are invisible, and other milliseconds create human-visible effects. I don't own any appliance that's a defacto EMP bomb, but even a single analog television set took out an entire town's DSL infrastructure (it really happened). Now, imagine a super-EMI appliance (Imagine; The 0.001% of the worst EMI-emitters, that's still a few out of a million) being right next to a computer, injecting EMI through a cheap computer power supply, and then really dirtying all the voltages inside the computer, creating those massive double-digit-percentage-loss errorcorrection/ECC bus floods that creates multithousand human visible millisecond-scale microfreezes (aka stutter).

A 1990s computer crashes, but a 2020s computer is full of error correcting buses & behaviors. So, thusly, the said computer is no longer guaranteed to crash;

Even today's PCI Express bus isn't like a non-errorcorrected 2400 baud modem that spews garbage when somebody else picks up the phone line (qF2{TfRJZ^s-y,a....NO CARRIER) while you were calling a BBS. Today, a PCI Express bus (in conjunctsion with PCI Express peripherals) is a packetized "error detection and retransmit mechanism". Yep. LAG, if there's a million-retransmit flood. Those bus lines are almost literally getting more like a DSL phone line now (just a different order of magnitude; the multi gigabit scale). While yesterday's PCI had error detect and retransmit, tomorrow, PCI 6.0 will have FEC too (forward error correction) so error corrections out of the wazoo because buses are getting faster and more sensitive to EMI! PCI Express is capable of lagging noticeably if tons of of packets are lost, for example. Same for NVME, SSDs, USB buses, etc. Any EMI could go anywhere, like a chip pin thanks to a cheap chinese design oversight, and whatnot that was not detected by automatic circuit board EMI-checking software, etc. BOOM. Lag instead of crash. There's billions of potential weak links in a modern computer (counting on-chip stuff -- even a single transistor can sometimes be a Chaos Theory Butterfly) and you only need enough weaknesses here n there. See, engineers? (Like the way I school disbelieving engineers about 240Hz benefits).

Heck, today DisplayPort and HDMI 2.0 is also an error-correct packet system now. Yep. Packets with error correction. On your cable between computer and monitor. Also, recently, very slightly variable latency sometimes occurs on DisplayPort and HDMI, though usually in the sub-millisecond timesales (<0.1ms), and most monitors just glitch (brief blackouts) though some freezes the last refresh cycle on-screen while it's trying to get the next refresh cycle. It might even happen more often as video cables try to go faster (HDMI can now go up to 77 gigabits per second over copper. That's almost as fast as 100 gigabit Ethernet), as electronics in display decides to lag (freezeframe the last refresh cycle) instead of doing blackouts, etc. LAG, baby. It ain't 1990 Toto, we're not in Kansas anymore. Many buses in a 2020 computer have "error-detect-and-retransmit" mechanisms -- probably over one hundred of them (from USB layers, PCI-X layers, SATA layers, NVMe layers, etc, etc, etc, etc). And y'know, engineers, do you know what "error-detect-and-retransmit" means, buddies? LAG. Yes, nanoseconds, but there is such a thing as error floods and deaths by a million nanoseconds to human feelable milliseconds and microfreezes galore.

Yesterday 1985 IDE bus .... CRASH upon EMP
Today's 2020 nVME .... LAG upon EMP (error retransmit)

Yesterday's 1985 ISA bus ... CRASH upon EMP
Today's 2020 PCI-Express ... LAG upon EMP (error retransmit)

Yesterday's 1985 RS232 serial bus ... CORRUPTION
Today's 2020 USB ... LAG upon EMP (error retransmit)

etc, etc.

See...We're Blur Busters. We're truly in the temporal technology business (Hz/lag/GtG/MPRT/stutter/sync, all a matter of temporals), and thusly, we keeps an open mind on whac-a-mole of the hundreds of weak links in a system, including longshots. We're science and evidence-minded here.

Milliseconds (many scientifically proven human visible) pays the bills that put the food on my table and pays my mortgage. We do realize that we attract a lot of "out there" people, but we also pull the Wizard of Oz curtain to reveal amazing temporal discoveries in the midst of FUD/disinformation.

I frequently have to give the Obviousman Duh walls-of-texts to many people throughout the industry, to mythbust all those tiny descendants of "Human Can't Tell 30fps vs 60fps" myths. Sometimes via great show-and-tells like a simple TestUFO animation. Whether be 360Hz monitors, 8000Hz mice, or other formerly-assumed imperceptible things. Assume is a no-no for researchers; so we actually dig and and find surprises. So, please allow me to microp that EMI is becoming an increasingly more frequent problem today in computer latency. (Excuse me.)

Historically, I'd find it nuts to put a Faraday Cage around a computer monitor, but I've seen everything -- the LG 5K monitor EMI-sensitivity problem isn't the only culprit! For every reliably EMI-sensitive device (e.g. the LG 5K recall), there's thousands of EMI-less-sensitive situations where 1000 units out of 1000000 actually had a definite case (e.g. more-sensitive-than-usual to some form of EMI creating lagging or glitching or other non-crash effects from EMI) -- whether manufacturing tolerances varying or the users being closer to EMI superemitters. Those don't make media, those don't make the news, those often get swept under the rug as unreproducible/unexplainable. So "designed-correctly" won't work if you've got an unavoidable defacto nuclear bombesque EMI source nearby.

Also EMI is a massive universe (radiofrequency through the air versus through the wires, of all kinds of strengths, all kinds of frequencies, of all kinds of looks on an oscilloscope ranging from tuning-fork looks to 1920s sparkgap transmitter looks), so EMI isn't just "one thing", and sometimes one defective appliance EMI super-emitter is >10,000,000 times stronger at a specific frequency for a specific instant than the EMI of an iPad. Like a failing CRT flyback transformer unknowingly shorting/arcing to the house's wiring (mains and/or phone) and turning the whole town's grid into a DSL-killing radio antenna

Or more mudane stuff such as:
- Neighbour's defective motor in a very old dryer.
- Roommate's 1970s music equipment with defective power supplies.
- Grandpa's 1940s electric fan running in workshop.
- Upstairs apartment tenant's failing fridge compressor.
- Nearby nerd's tesla coil build down the street generating intense spark-transmitter style background noise.
- Undiagnosed arcing between wires in your attic.
- The next door hospital's old MRI machine on its original power supply.
- That sketchy-looking huge rusting old 11kV power company transformer on the pole just outside your 2nd floor window.
- Large flash tubes (large xenon photo flashes, old dental analog X-ray, etc) and their associated capacitor/inductor/transformer circuit.
- Unshielded sparkplugs in a nearby old gas generator on the opposite side of the wall (exerior wall of your office).
- Or other super-EMI-emitters emitting blindingly hundreds or thousands or even millions times beyond FCC limits.

Most won't be problematic, but sometimes it is a problem (I've seen an Arduino crash from a single open-air sparkplug 2 meters away, and a RIM 950 BlackBerry pager irreparably die from a nearby Xenon flash tube/circuit two inches away! And other times, the problematic EMI sphere from the superemitter is big enough to envelope the whole residence, with no way to move your computer far enough outside the EMI sphere, or the EMI is in the wiring instead of the air. Like the example of an appliance weirdly creating unexplained microfreezes in window-dragging on a nearby computer.

Many engineers just check their circuit design through vetting software, send to fabricators such as PCBway or whatever, do a small beta, and then ship out the retail, call it a day. Don't cry to me if 1000 of the 1,000,000 retail users has a next-door neighbour having an EMI-superemiitter appliance that is doing wonky things to their setup....just because one circuit trace or one chip wasn't properly shielded, and/or the user was using a tempered-glass-sided computer tower that wasn't a complete Faraday cage (EMI via air)...and/or the power supply was defective in shielding specific power frequencies (EMI via wire), and/or multiple concurrent factors. Doh?

FCC has no God Mode that can wave a wand and make all those EMI superviolators dissappear. Unfortunately no better-than-FCC/UT/ETL/ISO/KitchenSink Approved Shielding, will be 100% completely opaque to 100% all of EMI frequencies of 100% of all EMI superemitters lurking worldwide. Lot of the superemitters are often only short-distance (inverse square law FTW!), killing only a couple computers with lag/crashes, but doing zilch for the rest of the town. FCC ain't going to hunt this particular superemitter down, since it's not causing thousands of complaints. Anyway, we can only do our best.

At some EMI-strong point (e.g. a nuclear bomb), no shielding of standard retail computer builds is immune to such strong EMI of the EMP pulse of the bomb. Shielding isn't completely opaque to all radiofrequencies; and sufficiently strong EMI of various frequencies will tend to punch through garden-variety computer shielding. But plenty of lesser EMI-superemitters (whether by air or via wire) capable of doing to a computer, lots of hard-to-troubleshoot stuff that feels voodoo.

Turn the dial somewhere between "EMI successfully blocked by shielding" and "Nuclear bomb league EMP pulse", and some computers will find the sweet spot (lagging computer) at EMI signal strengths just barely below causing computer crash. It may only be a specific EMI frequency/pattern, and immune to other EMI frequencies/pattern of the same signal strength. And yes, many systems just crash, but more often, computers now begin lagging first when the EMI is a smidge below computer-crashing-strength.

So.... "Properly Designed" doesn't five-sigma-out the FCC-violating EMI super emitters that probably exists by the millions throughout North America -- who knows how many there are -- but it's somewhere "Rare enough that it doesn't affect a single beta tester" but also "Common enough to affect a few retail users". Mathematics 101. See?

It does sounds very tinfoilhattery, even to many University Ph.D engineer (especially those who don't know how error-corrected-out-of-the-wazoo a 2020 computer is), but, alas, EMI super-emitters exist here and there, that can indeed visibly lag a specific computer, glitch a specific monitor, or create weird non-crash effects on specific devices. Super-rare, and it's probably certainly not the problem of most of the forum members troubleshooting unexplained lag (found even in window dragging and offline gaming), but it's certainly extant.

But yes. Obligatory troubleshooter wasted-time warning. This is a wild goose chase to red herrings more than 99% of the time. It's much rarer than two-sigma, but more common than five-sigma, but it's now rapidly becoming more common thanks to the more-EMI-sensitive faster speeds. And yes, there's placebos & wrong claims in the mix too, which muddy the signal-noise ratio finding trustedly actual EMI-lagged computers. And, definitely, focus on more common causes of lag first.

</MicDrop>

[MatrixQW]

I'm sure someone else has said this before but as an electrical engineer, I can tell you that EMI should have zero effect on your "input lag"

What about grounding?

When I slide my fingers over both sides of my PC case I can feel a vibration and a buzzing sound. Same happens in the kitchen with the oven and dishwasher.
Can that affect components?

[howiec]

So.... "Properly Designed" doesn't five-sigma-out the FCC-violating EMI super emitters that probably exists by the millions throughout North America -- who knows how many there are -- but it's somewhere "Rare enough that it doesn't affect a single beta tester" but also "Common enough to affect a few retail users". Mathematics 101. See?
-----
But yes. Obligatory troubleshooter wasted-time warning. This is a wild goose chase to red herrings more than 99% of the time. It's much rarer than two-sigma, but more common than five-sigma, but it's now rapidly becoming more common thanks to the more-EMI-sensitive faster speeds. And yes, there's placebos & wrong claims in the mix too, which muddy the signal-noise ratio finding trustedly actual EMI-lagged computers. And, definitely, focus on more common causes of lag first.

Thanks for the detailed response and clarifications. I totally agree with all you stated which is why I used probability adverbs and do not completely dismiss EMI as a potential cause of problems.

I just think it's usually the wrong route for the majority of people to go down and people are easily mislead to focus their efforts on the wrong things. Looking at some of the pictures in this thread of homemade, completely ineffective faraday cages with huge gaps in multiple places is a perfect example of wasted effort.

If indeed someone suspects EMI as a problem (assuming all other PC troubleshooting aspects have been exhausted), then be forewarned, it is not an easy problem to completely solve, e.g. building an effective faraday cage for your PC is not easy or cheap to do and you really need to know what you're doing (amateurs will most likely get it wrong). The best recommendation I can give is to get help from someone who really knows the subject and can physically be there (e.g. expert in EMI, has access to a good real-time spectrum analyzer, is an expert with PCs from both a HW and SW perspective) or be prepared to potentially spend a lot of time and money trying to learn and troubleshoot.

What's funny is that I have my PC case open and can hear a difference in this constant high pitch whine that starts to sound more "pulsating" whenever I am moving my mouse (NOT placebo, I've tested this many times and is happening right now). So yes, I'm sure our PCs are not bulletproof from an EMI view and there are plenty of bad designs or defective hardware out there. One just really needs to be careful about specifically blaming input lag on EMI when more often than not, the culprit is primarily a culmination of other things.

[nuggify]

since it would kind of indicate extreme (?) levels of radiated EMI in the air even, that sounds like a potential health hazard even ?

Like I have previously stated, I do not believe this is caused by EMF. I have Trifield TF2- a good enough gauss meter to see if my EMF levels are elevated. They are not, they are consistently under or near 2mg throughout my home. I do have elevated EF (electric fields) especially near my cables (PC), and have found some strange behaivor while measuring these.

I do not believe the cause is radiated. If it was then using my Online UPS on battery (not plugged in) would not fix the issues like it does. That being said, I have no clue why applying shielding to cables and hardware in our cases has a very apparent affect on the problem. My guess is the noise floor is raised when we have continuity with our AC mains.

Thanks for the detailed response and clarifications. I totally agree with all you stated which is why I used probability adverbs and do not completely dismiss EMI as a potential cause of problems.

I just think it's usually the wrong route for the majority of people to go down and people are easily mislead to focus their efforts on the wrong things. Looking at some of the pictures in this thread of homemade, completely ineffective faraday cages with huge gaps in multiple places is a perfect example of wasted effort.

If indeed someone suspects EMI as a problem (assuming all other PC troubleshooting aspects have been exhausted), then be forewarned, it is not an easy problem to completely solve, e.g. building an effective faraday cage for your PC is not easy or cheap to do and you really need to know what you're doing (amateurs will most likely get it wrong). The best recommendation I can give is to get help from someone who really knows the subject and can physically be there (e.g. expert in EMI, has access to a good real-time spectrum analyzer, is an expert with PCs from both a HW and SW perspective) or be prepared to potentially spend a lot of time and money trying to learn and troubleshoot.

Awesome to see an EE chime in here. This is a problem that I have dealt with for 2 years now, others even more. We are determined to find out the cause of this. There are in fact many of us suffering this. I can tell you without a doubt this is an electrical issue. I have replaced every single piece of hardware I own, including all cables, modems routers, and connections at the ISP drop, at least 3 times now. Literally every component of my system has been completely switched out with no results. My laptops, desktops, TVs all display this issue. And things like ferrite and toroid cores, Online UPS systems, Power conditioners, Isolation transformers, installing additional ground rods all have a very noticeable impact on the problem- but do not provide a solution. The one and only thing that works to actually fix it is unplugging my UPS and running off the battery for the few minutes. Of course at other locations (friends places in other cities) my hardware works perfectly. All of my hardware is very high end (platinum and gold rated PSUs).

Obviously the faraday cages are not ideal. But the reason people post about them here is because it makes instantaneous noticeable differences in how the issue manifests (although nearly always temporary).

We have a discord with near 50 people with very close to identical symptoms. And they too have all tried brand new hardware. If you would like to follow along with our experiences and tests, and potentially provide some insight it would be much appreciated and I can PM you an invite. We have people using oscilloscopes and have found some large harmonic distortion on their mains. I personally do not believe this problem is caused by EMI, or EMF. Otherwise my Online UPS should fix it end of story. Maybe RFI but I do not have a spectrum analyzer to investigate that yet, and I would think high levels would cause things to malfunction much worst than this.

A post on this very website confirmed that this (harmonic distortion) can be a possible cause for issues very similar to this, you may be interested:

viewtopic.php?f=2&t=6064&start=10

I have extensively had my electrical checked by both POCO and multiple high end electricians. There are some abnormalities but the obvious things have been checked and or redone. Even going so far to have my neutral feeders to my home completely replaced. This problem is not caused by anything obvious. Electrical devices act very strange in my home though and it certainly warrants more investigation.

But yes. Obligatory troubleshooter wasted-time warning. This is a wild goose chase to red herrings more than 99% of the time. It's much rarer than two-sigma, but more common than five-sigma, but it's now rapidly becoming more common thanks to the more-EMI-sensitive faster speeds. And yes, there's placebos & wrong claims in the mix too, which muddy the signal-noise ratio finding trustedly actual EMI-lagged computers. And, definitely, focus on more common causes of lag first.

</MicDrop>

I know you continually want to warn people not to go on a wild goose chase with this. But it is very clear to me many folks do in fact suffer this problem. To anyone that has what they think to be this issue, you should verify entirely that it is not you hardware, then take your hardware to another location far from your home and test. If it operates normally then you do indeed have this issue.

This is a very real and a very strange problem. I appreciate that you have allowed us the space to discuss this publicly as there are more out there suffering this and they should know that this is possible and they are not alone.

[Chief Blur Buster]

If indeed someone suspects EMI as a problem (assuming all other PC troubleshooting aspects have been exhausted), then be forewarned, it is not an easy problem to completely solve, e.g. building an effective faraday cage for your PC is not easy or cheap to do and you really need to know what you're doing (amateurs will most likely get it wrong). The best recommendation I can give is to get help from someone who really knows the subject and can physically be there (e.g. expert in EMI, has access to a good real-time spectrum analyzer, is an expert with PCs from both a HW and SW perspective) or be prepared to potentially spend a lot of time and money trying to learn and troubleshoot.

Indeed, there's so many EMI frequencies and EMI strengths that no Faraday Cage can ever be perfect. That metal Faraday cage is opaque to many frequencies (extreme example: AM Radio) but other frequencies (extreme example: X-Rays) just punch through it just as if it was mostly transparent glass. The better/more complete/gapless the Faraday cage design, the more frequencies can be attenuated to bigger degrees.

Now, I make no comment on DIY Faraday cages which are easily ineffective by user inexperience (without measuring equipment), but the back of an LCD is made out of metal (metal encased glass), and the VESA mount square (for stand) is also made out of metal. So in theory, the partial Faraday cage may sufficiently "complete" the cage partially for certain common frequencies like 2.4 Ghz WiFi that has been problematic for some unshielded electronics -- the "monitor motherboard" is located in the bottom few inches of the monitor, where the ports are, and are already encapsulated in metal, though there are a lot of vent holes and jack holes (USB, DVI, DP, etc) that are tantamount to small holes in a Faraday cage, especially if some of the jacks are not shielded themselves (e.g. plastic jacks), some manufacturers make those shielding mistakes.

Anyway, in theory you only need to wire-mesh the rear of the monitor, cover all the unused ports, and as close as possible to the VESA monitor stand (since it's already metal at that centre). That DIY Faraday Cage, however, may mitigate a pre-recall LG 5K monitor since the 2.4Ghz WiFi frequencies will often be blocked by that metal mesh of that density (just like a microwave oven window screen).

Now, this only assumes you're trying to protect the monitor from nearby routers (including your neighbour's router on the opposite side of the wall that your computer desk is facing), if that was THE interference source, though moving the monitor would be much easier (inverse square law)

That mesh is certianly transparent to a whole lot of other frequencies though and I do not think the monitor would be the side causing latency at this stage, from what I now about most firmware handling. Most of the time, strong interference injected into a monitor either causes blackouts, video noise, digital noisebars (corresponding to LDVS cable boundaries), or freezeframes, etc.

Most monitor manufacturers are already properly shielding the innards of the monitor (the monitor motherboard mounted on the rear of the monitor, so it's highly improbable it is a cause of latency though, and likely not be helping here in this case. More likely (if RFI-based) some injected interference somewhere else.

It's easy to bark up the wrong tree with these measures...

[nuggify]

Indeed, there's so many EMI frequencies and EMI strengths that no Faraday Cage can ever be perfect. That metal Faraday cage is opaque to many frequencies (extreme example: AM Radio) but other frequencies (extreme example: X-Rays) just punch through it just as if it was mostly transparent glass.

If mitigation is possible, it will need to be highly targeted mitigation, meaning we will need to know what frequencies and wavelength is causing this in the first place.