Why do [some] 240HZ monitors have more lag than 144HZ AHVA

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Re: Why do 240HZ monitors have more lag than 144HZ AHVA

Post by Chief Blur Buster » 23 Jan 2018, 13:44

KKNDT wrote:"Lag competition between 240HZ TN and 165HZ IPS" is a very hot topic around me. However my knowledge is insufficient to asnwer it.That's why I open this thread here. Till now most people I know do trust TFTcentral's result. I believe 240HZ TN is sure to win regarding lag randomness factor explaned here. But who wins on absolute lag? I still can't find a authoritative saying whose data is more reliable?

RTINGS: XL2540 3.7MS VS XB271HU 4.6MS
TFTCENTRAL: PG258Q 4.6MS VS PG279Q 3.25MS, SMTT 2
TOM'S HARDWARE: PG258Q 20MS VS XG2703-GS 31MS
Tom's Hardware seems to use Leo Bodnar (60Hz) so drop that result.
EDIT: Not quite, but something similar via high speed video

RTINGS and TFTCentral is much closer to true absolute lag for 240Hz.
RTINGS currently electronically measure to the GtG1% point (essentially, the beginning of visibility of pixel transition)
TFTCentral currently visually compares a SMTT 2.0 photograph, to find the beginning of GtG.

In TFTCentral's graphs, they add a "band" representing manufacturer GtG (that's, however, the GtG10%->90%). I don't know what Adam Simmons of TFTCentral declares the beginning of GtG, but I think first "faint fade" edge of pixel response -- meaning the lowermost faint appearance of lag digits in SMTT 2.0 photo. That would correspond to the beginning of GtG. For a 1/1000sec photograph on a 1000fps VSYNC OFF test (SMTT 2.0), the error margin is ~1ms (1080p@120Hz 135KHz scanrate, that error margin is 135 scan lines, or about 8% the height of a 120Hz refresh cycle). So I would ignore decimal digits of TFTCentral numbers.

However, TFTCentral numbers are pretty uncannily accurate (compared to Leo Bodnar) considering they are human-eye inspection of SMTT 2.0 photographs -- it is darn impressive how a human-eye inspection of a SMTT 2.0 photograph can yield ~1ms lag-test accuracy (confirmed by me). Just mostly discount the numbers to the right of the decimal point, though. If many runs are done, e.g. 10 runs, you can get better than 1ms accuracy for SMTT 2.0 lag tests. But only to a certain point.

I do trust the numbers to the left of the decimal point for RTINGS numbers and TFTCentral numbers for max-Hz absolute lag measurement to an accuracy margin of approximately 1ms error (for all the unknownn factors, like digital cable latency -- like DisplayPort micropackets, etc).
KKNDT wrote:As far as I can conclude, display-only lag is affected by:

1. Signal processing lag (scaling/buffering... etc.)
2. Scanout lag
3. GTG
4. maybe something missed
Cable lag too. There are lag differences in cables.
In lowest-to-highest, is VGA -> (HDMI, DVI) -> DisplayPort.

- VGA is analog and RAMDACs have little lag (virtually lagless).
- HDMI, DVI is digital and requires a little bit of codec lag to convert the digital into a modulated signal over the cable, which is then demodulated on the remote end.
- DispayPort is micropacket based, so there's also packetization lag added on top of digital codec lag.

Even different HDMI version numbers and different DisplayPort version numbers have lag differences (in the hundred-microsecond difference scales). Meaningless for most, but makes decimal digits in most lag benchmarks harder to compare across sites.

It's very tiny (often sub-1ms difference) but when attempting to measure display lag to decimal digits (e.g. 0.1ms) cable lag becomes a massive error margin for decimal digits after the millisecond number.

That's why I would mostly discount decimal points in most lag test numbers (especially if different HDMI version numbers, or only treat them as "relative lag" numbers, as long as the same cable connection is used.

It's still useful to publish the decimal points, since comparing modes, comparing cables, comparing between monitors, on a relative basis (Same outout of the same graphics card), the decimal digit can then become useful (if the error margin of the testing method allows it -- not SMTT 2.0), albiet not for comparing across different websites.
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Re: Why do 240HZ monitors have more lag than 144HZ AHVA

Post by hkngo007 » 24 Jan 2018, 01:36

Chief Blur Buster wrote:
KKNDT wrote:As far as I can conclude, display-only lag is affected by:

1. Signal processing lag (scaling/buffering... etc.)
2. Scanout lag
3. GTG
4. maybe something missed
Cable lag too. There are lag differences in cables.
In lowest-to-highest, is VGA -> (HDMI, DVI) -> DisplayPort.

- VGA is analog and RAMDACs have little lag (virtually lagless).
- HDMI, DVI is digital and requires a little bit of codec lag to convert the digital into a modulated signal over the cable, which is then demodulated on the remote end.
- DispayPort is micropacket based, so there's also packetization lag added on top of digital codec lag.

Even different HDMI version numbers and different DisplayPort version numbers have lag differences (in the hundred-microsecond difference scales). Meaningless for most, but makes decimal digits in most lag benchmarks harder to compare across sites.

It's very tiny (often sub-1ms difference) but when attempting to measure display lag to decimal digits (e.g. 0.1ms) cable lag becomes a massive error margin for decimal digits after the millisecond number.

That's why I would mostly discount decimal points in most lag test numbers (especially if different HDMI version numbers, or only treat them as "relative lag" numbers, as long as the same cable connection is used.

It's still useful to publish the decimal points, since comparing modes, comparing cables, comparing between monitors, on a relative basis (Same outout of the same graphics card), the decimal digit can then become useful (if the error margin of the testing method allows it -- not SMTT 2.0), albiet not for comparing across different websites.
That is very interesting information. It makes me curious as to how cables such as say, VGA to DVI adapters or DVI to DP would perform? Would they have more lag because they are like adapters?

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Re: Why do 240HZ monitors have more lag than 144HZ AHVA

Post by KKNDT » 24 Jan 2018, 09:15

Chief Blur Buster wrote: Tom's Hardware seems to use Leo Bodnar (60Hz) so drop that result.
EDIT: Not quite, but something similar via high speed video
Thank you chief. I learn a lot every time I read your post.

I think Tom's hardware uses high speed camera and they have mentioned that they do test HZ greater than 60HZ.

http://www.tomshardware.com/reviews/dis ... 901-4.html

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Re: Why do 240HZ monitors have more lag than 144HZ AHVA

Post by Chief Blur Buster » 24 Jan 2018, 10:03

KKNDT wrote:Thank you chief. I learn a lot every time I read your post.

I think Tom's hardware uses high speed camera and they have mentioned that they do test HZ greater than 60HZ.

http://www.tomshardware.com/reviews/dis ... 901-4.html
You are right! Seeing numbers very similar to Leo Bodnar, made me think that. But their technique produces similar "high" results.

I've edited my original post to get the correct info. They actually do: their high speed camera lag test.

That said, I see caveats with their test.

- Lag stopwatch start: ?
.....How quickly does their signal generator begin generating a white field? (Is there a signal generator lag?)
.....Does their stopwatch start exactly at the VBI of beginning to transmit the signal? (I assume yes)
.....Does their signal generator work at 240Hz? (Unknown)

- Lag stopwatch end: VSYNC ON
.....They wait for a full white field refresh, probably GtG100%.
.....Which is equivalent to a VSYNC ON method of lag test, bottom-edge. Therefore, Tom's Hardware lag tests are more useful for consoles (VSYNC ON) rather than eSports (VSYNC OFF).
.....Their technique, if measured at only 1080p and at only 60Hz, would be a similar number as Leo Bodnar "Bottom" square plus up to a few extra milliseconds for GtG100% (since they said full white field).

Signal generators begin generating their frame at the top (VSYNC ON) so signal-generator-based lag tests produce numbers equivalent VSYNC ON lag tests. SMTT 2.0 is a VSYNC OFF lag test, so SMTT 2.0 (that TFTCentral uses) is much closer to eSports interests.

I will eventually catalogue all the different website's lag testing methods and describe their differences, their pros/cons, and their applicabilities.

VSYNC ON + bottom edge + GtG100% = very large lag numbers.
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Re: Why do 240HZ monitors have more lag than 144HZ AHVA

Post by q8fawaz » 08 Feb 2018, 09:48

hkngo007 wrote:Hello,

Just wanted to share my personal experience on this matter as I have:
1. TN 120hz gaming monitor - Samsung S27950D (used this for about 6 years)
2. IPS 165hz gaming monitor - Viewsonic XG2703-GS (used this for about 1.5 years?)
3. TN 240hz gaming monitor - ASUS PG258Q (used this for about .5 year?)
4. IPS 165hz gaming monitor - ASUS PG279Q (this is my friends, but I've used it on severaaal occasions)

I'd like to confirm so far that indeed, the 165hz (OC'd) IPS gaming monitors above have lower input lag/signal processing than the 240hz TN monitor. This is unfortunate for me and I'll explain my failure on this shortly.

Just FYI, I've played FPS shooters for like 20 years, from CS 1.5, to CS 1.6 -> CS GO, Battlefield 3,4, 1, Left for dead 2, Team Fortress 2, Killing floor 2.

So my latest purchase was the PG258Q. Prior to this purchase, I was using the IPS 165hz. The experience with the IPS 165hz was great visually because it was 1440p, better angles and colours, but input lag wise it felt pretty similar to my 120hz in this department but was good. Motion blur was bad, I immediately noticed significantly more blur going from 120hz TN to 165hz IPS (but I got used to it eventually). My gaming performance is probably about the same overall but the enjoyment has increased due to better details from resolution and colours and viewing angles.

I started to get a bit more interested in monitors at this point, and obsessed with the hertz and TN vs IPS and all that good stuff and came across blurbusters own article on GSYNC/input lag which was very detailed (although I didn't understand it for ages because my brain is just stupid that way), and also read a lot of reviews of monitors from TFTcentral, Tomshardware, PCmonitor Info, Battlenonsense (and some other random ones).

In the end, I got sucked into the high hertz marketing and didn't fully understand the elements of input lag that point in time, such as signal processing which was the most significant factor for me (and TFT central had this captured quite well), opposed to pixel response time (blurring etc). It didn't help that different sites used different methodologies as well.

Ultimately I relied on Tomshardware (lowest black to white time) + Battlenonsense (low button to pixel delay) + blurbuster (higher hertz = lower delay (scanout time?))which showed very low levels of "lag" for the PG258Q. I went and bought the PG258Q.

Here are my experiences so far (also I have a 1080ti + play on low and can sustain 200-500 FPS easily):

Pros of the PG258q compared to IPS 165hz
- the image/my movements felt a lot smoother
- i could see a lot better when scanning around
- in some games, or situations within the same game, I appeared to better because I could see and respond faster (like moving around in battlefield 1 - scanning for an enemy hiding somewhere or running in peripheral vision)
- the controls to navigate monitor settings is so much better with the joystick
- monitor design looks better imo

Cons of the PG258q to IPS 165hz
- bad resolution, everything is more blurry (not motion blur, just image quality in that sense) (native 1440p vs 1080p upscaled to 1440p is no competition, at least on these monitors).
- worse colours duh (having it side by side you can tell the extreme difference)
- smaller screen - found it a lot harder to see enemies heads after coming from 27" 1440p (of course I got used to it after a couple weeks)
- asus pg258q seems to have problem with the sound not working (or something is wrong with my system - but many others have reported similar issues in regards to ASUS built in speakers. I don't use them, but still, it's part of the monitor I've paid for)
- increased input lag - slightly but noticeable, especially during the actual aiming/recoil control. Now, against most average/okay players in the FPS game, it didn't matter much, I'd still win the gunfight but I certainly felt it wasn't as connected and responsive, and I'd miss a few more headshots that I would have sworn 100% that it was a sure kill. HOWEVER, when it was against a really good player at my level and higher, that's where I felt it the most. I'd find the input lag disadvantage much more noticeable and instances of "what the f, I know I headshot that guy, I know I shot him first, he should be dead I know this" happened a lot more against those same players (had to luxury to play against some of these players over the months).

So I reverted back to my IPS 165hz, and boom, I could instantly feel the difference. Those shots that I sworn I could have had, registered, the recoil was more controlled.

I also performed maybe 5-10 minutes each time I played (maybe 5-6 days a week), comparisons of button to pixel delays in battlefield 1 by shooting guns, and observing how long itd take to register on screen (yes I know there's margin of error, but when you've played FPS for that long, you notice things) and switching monitors of repeating this. I also did left to right movements, where I'd move and wait for screen to register the movement and immediately move the opposite direction and this once again showed the TN 240hz had more input lag. I also used my friends PG279q on many occasions and noticed very similar things, (the PG279q is actually even faster than my XG2703-GS).

Ultimately, my gaming performance is still very good (I regularly get top score in battlefield 1 in a 64 player map - this is not bragging, but just emphasising the increased input lag isn't really that bad), however in the competitive scene (CS GO or really good aimers), I often struggle more. Of course, TFTcentral showed the processing lag to be higher at 2.9ms for the PG258Q TN 240hz, but I was stupid and didn't understand that at THAT time prior to purchase.

I'm now going to sell the PG258q at a loss, because overall, I play better with the IPS 165hz and get more enjoyment from the higher resolution, colours, viewing angles, despite the higher motion blur. I will be relying more on TFTcentral in the future on the signal processing portion (I know PCmonitor info combines signal + pixel response, however they don't separate it so that is annoying, because if they did I could compare results against TFTcentral).
So asus is faster then 240hz cuz i have 240hz already but it feel not responsive

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Re: Why do 240HZ monitors have more lag than 144HZ AHVA

Post by KKNDT » 09 Feb 2018, 08:43

Chief Blur Buster wrote:
RTINGS and TFTCentral is much closer to true absolute lag for 240Hz.
RTINGS currently electronically measure to the GtG1% point (essentially, the beginning of visibility of pixel transition)
TFTCentral currently visually compares a SMTT 2.0 photograph, to find the beginning of GtG.
Chief, I have 2 question here:

1. Do you need to keep the 2 screen at the same HZ if you measure the lag using SMTT 2?
2. What does the result represent?/ What lag exact is SMTT 2 meant to measure?
I have read TFTCentral's input lag article. In this article the developer of SMTT says "signal delay + input lag + response time + x". TFTCentral's input lag defination seems only contains signal processing and G2G. They never say something about the lag jitter caused by scanout cycle.

I have also read RTINGS's article
RTINGS understand how scanout impacts the lag number, but their published numbers exclude the scanout factor, since the numbers are called "lowest input lag possible", is it right?

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Re: Why do 240HZ monitors have more lag than 144HZ AHVA

Post by Chief Blur Buster » 09 Feb 2018, 11:04

KKNDT wrote:Chief, I have 2 question here:
1. Do you need to keep the 2 screen at the same HZ if you measure the lag using SMTT 2?
Yes, you have to with SMTT 2.0. You need perfect output mirroring. Exact same CRU timngs. Don't use adaptors, adaptors add lag.

To be very sure, swap the inputs, and measure again, make sure differential is still the same, so you don't have "input-related-differences" in input lag (e.g. DisplayPort has different input lag than HDMI)

SMTT 2.0 lag is much closer to "min-lag". It's 1000fps VSYNC OFF, so scanout lag is only 1/1000th what is normally is. So scanout lag is essentially removed from SMTT 2.0 results. That's why SMTT 2.0 numbers are more useful for VSYNC OFF game players than VSYNC ON game players.
KKNDT wrote:2. What does the result represent?/ What lag exact is SMTT 2 meant to measure?
I have read TFTCentral's input lag article. In this article the developer of SMTT says "signal delay + input lag + response time + x". TFTCentral's input lag defination seems only contains signal processing and G2G. They never say something about the lag jitter caused by scanout cycle.
They certainly don't cover much in that aspect, BUT the SMTT 2.0 is very close to numbers that are important to CS:GO players that use VSYNC OFF which bypasses a lot of scanout lag.
KKNDT wrote:I have also read RTINGS's article
RTINGS understand how scanout impacts the lag number, but their published numbers exclude the scanout factor, since the numbers are called "lowest input lag possible", is it right?
That's good for VSYNC OFF players.

Average scanout lag is half a refresh cycle.

(Framerate double refresh rate) = one-halved scanout lag lag factor in average lag number.
(Framerate quadruple refresh rate) = one-quarter scanout lag factor in average lag number
(Framerate eight times refresh rate) = one-eighth scanout lag factor in average lag number

So 480fps at 120Hz = one-quarter of one-half refresh cycle = one-eighth refresh cycle scanout lag graident error factor.

So the higher your video game framerate is above refresh rate, the less important scanout lag is to absolute lag.

These ultra-detailed lag analysis is extremely useful for smart interpretation:
VSYNC OFF Average equals Average = Scanout lag of framerate matching refresh rate.
VSYNC OFF Average equals Min = Scanout lag of infinite framerate VSYNC OFF
VSYNC OFF Average equals Between Min and Average = Scanout lag of finite framerates higher than refresh rate.

So it's okay to exclude scanout lag when publishing lag numbers for the CS:GO eSports audience (e.g. VSYNC OFF lag numbers).

Since SMTT 2.0 is 1000fps VSYNC OFF, it output numbers almost equal to infinite-framerate VSYNC OFF, since for 1000fps VSYNC OFF scanout lag error margin is only 0.5ms for SMTT 2.0 Therefore, RTINGS Min roughly corresponds to SMTT 2.0 Min to the nearest millisecond, literally! There's a slight lag offset because of cable lag (e.g. HDMI vs DP vs etc -- 1-2ms differences), but the lag numbers will increase/decrease proportionally if both test techniques are done on the same display. Meaning numbers increase/decrease in exactly the same way, both sets of numbers being VSYNC-OFF-biased.

IMPORTANT: There is a distinction between scanout-waiting lag and scanout-lottery lag. VSYNC ON has a scanout-waiting effect, and VSYNC OFF has a scanout-lottery effect. This is because a page flip occuring randomly, will have a lag between (0...one refresh cycle) for any given random pixel on the screen, assuming a realtime scanout panel. It also depends on whether you're measuring a single pixel or first-anywhere-reaction.

Four Lag Metrics: Assuming realtime panel scanout: panel scanout fully in sync with signal input scanout
  1. VSYNC ON, monitoring a single pixel:
    You have a scanout-random lag effect that increases towards the bottom of screen. There's a vertical lag gradient.
  2. VSYNC OFF, monitoring a single pixel:
    You have a scanout-lottery lag effect, but you have no lag difference between top/bottom edges for realtime-scanout panels, when you do many runs and average the runs. Numbers will typically vary in a range that's equal to a whole refresh cycle, but the averages will settle. There's no vertical lag gradient at all, for synchronous-scanout panels.
  3. VSYNC ON, first-anywhere-reaction:
    The top edge always reacts first, and almost always at a quite fixed interval.
  4. VSYNC OFF, first-anywhere-reaction:
    Very consistent average numbers which becomes equal to MIN the closer you reach infinite framerate.
Disengaging from old-fashioned single-number lag readings (they're either only useful to VSYNC ON players or only useful to VSYNC OFF players.... console lag measurements are useless for eSports lag measurements, and vice-versa). Lag measuring methods inherently always has a "sync bias". Which means the numbers are either mainly useful to VSYNC ON players, or the numbers are mainly useful to VSYNC ON players.

TomsHardware: VSYNC ON bias
RTINGS: Both (graphs), VSYNC OFF bias (lowest number)
TFTCentral: VSYNC OFF bias
Prad.de: VSYNC ON bias
DisplayLag.com: VSYNC ON bias
Etc.

Leo Bodnar = VSYNC ON bias
SMTT 2.0 = VSYNC OFF bias
Etc.

Bias can be accidental (Because of test method). But no matter what lag measuring method anybody invents, there's always a sync bias. There's no way to have a single number that has both a VSYNC ON and a VSYNC OFF bias. Console eSports players should focus on the sites with the VSYNC ON bias in their lag numbers. CS:GO players should focus on the websites with the VSYNC OFF bias.

Pandora's Box. Lag measuring is an incredibly complex topic. It's horribly much more complicated than I thought two years ago, and I now understand why. It also even hugely explains many weird differences between websites. I have even gained the ability to mathematically convert lag numbers between all the different websites (and they correspond). It's like studying quantum mechanics and trying to get a Ph.D in quantum mechanics. It's tantamount to doing the same for input lag!

Few in the world understands all the lag variables concurrently and simultaneously well enough to figure out why the numbers between different websites are different, and know how to mathematically reproject the different websites' lag numbers to the other sites: They're actually very consistent with each other (even with huge lag-number differences) -- but compensating for the differences in lag stopwatching methods, the numbers of the different websites actually lines up since I finally discovered almost all the "major" variables (except for minor ones beyond control).

I can now actually create a math model (aka math formulas) that essentially clicks all the numbers of all the lag-testing websites into the same lag-testing Venn Diagram, even those numbers that are as much >15ms different between two different websites for the same monitor. It will take me until 2018-2019 but I plan to be publishing a "Input Lag Formula" standard -- kind of the input lag equivalent of a Unified Theory for particle physics. This is a breakthrough development. I'm considering looking for paper co-authors (e.g. to create a paper similar to pursuit camera paper), please contact me for more information at mark[at]blurbusters.com since I believe what I have done is sufficiently breakthrough enough to be put into a paper. Researcher experience preferred (ResearchGate, etc).

In fact, what I have learned finally also explains why certain 144Hz and 165Hz panels is sometimes preferred by certain eSports players than certain 240Hz panels -- but not always. (This is unrelated to the ghosting differences -- that's a separate subject). Some players perform better on one, and different players perform better than the other. I think I know why but I need more testing time to exactly figure out why. If you are an eSports player who's confused about the 240Hz FUD but have an open mind to figuring out the scientifics, please email me, I would like to ask you more questions to help assist my testing.
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Re: Why do 240HZ monitors have more lag than 144HZ AHVA

Post by A Solid lad » 18 Feb 2018, 10:47

KKNDT wrote:
Chief Blur Buster wrote: Tom's Hardware seems to use Leo Bodnar (60Hz) so drop that result.
EDIT: Not quite, but something similar via high speed video
Thank you chief. I learn a lot every time I read your post.

I think Tom's hardware uses high speed camera and they have mentioned that they do test HZ greater than 60HZ.

http://www.tomshardware.com/reviews/dis ... 901-4.html
Can second this.
I've learned so much since I've started reading pots on this site, and 70% of the acquired knowledge came from Chief's posts.
(for example, I had no idea HDMI actually has lower input lag, than DP...though they worked the same way)
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Re: Why do 240HZ monitors have more lag than 144HZ AHVA

Post by Chief Blur Buster » 19 Feb 2018, 12:21

A Solid lad wrote:I've learned so much since I've started reading pots on this site, and 70% of the acquired knowledge came from Chief's posts. (for example, I had no idea HDMI actually has lower input lag, than DP...though they worked the same way)
It's only a rough generality, though -- and often only by a scant sub-millisecond scale. Also, HDMI specs vary. HDMI 2.0+ actually micropacketizes much more than early HDMI specs. Also, sheer dotclock allowing lag-reductions (e.g. Quick Frame Transport tricks) can often overcome the latency increases of more micropacketization overhead. Not to say, the best HDMI implementation can have microseconds less lag than a poor DisplayPort implementation, so it's not universally that HDMI has less lag than DP. When done properly, it's a molehill compared to a mountain.

That said, it's when different inputs vary in lag by several milliseconds (due to different scalers/processors on different inputs), that only now, this becomes a problem with highly competitive players.

Also, prioritize your causes of lag. More lag is caused by LCD GtG than from DisplayPort-vs-HDMI difference.
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Re: Why do 240HZ monitors have more lag than 144HZ AHVA

Post by romkkaa » 08 Apr 2018, 20:27

I have the same experience as hkngo007
Played first person shooters for 2 days switching between Predator XB271HU and Alienware AW2518H and I felt like I'm faster on the predator (faster aim, faster reaction time, spotting enemies quicker) despite the lower framerate cap (162 and 235 respectively). Planning to return the alienware back to the store tomorrow as I'm very disappointed in it. 240 Hz is a marketing trick, nothing more. Yes, motion clarity is better on the alienware but overall experience is bad.
sorry for my English

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