BenQ XL2730Z - What is required for smooth 1440p @ 120Hz?

[ismithers]

I had the XL2411Z and just upgraded to this monitor as I wanted something larger and with a higher resolution. I have an AMD R9 280 which is unfortunately not free-sync enabled, so guess what is on my Christmas list, however my questions are related to MBR as compared to the XL2411Z I am finding it difficult to find a configuration I think looks reasonable/as good. This is over a Dual Link DVI connection.

I have used the CRU to create a custom resolution of 2560x1440 @ 120Hz. I have not adjusted the vertical/horizontal totals yet as I am worried about the clock speed. At present the pixel clock speed is at 480.40 MHz (naturally I had to use the AMD Clock Patcher to go over 300MHz).

I wish to ask:
1) I notice that when I use the custom resolution, my MBR menu in the OSD has two new options: Intensity & Area. What are these?
2) Is the pixel clock being at 480.40 MHz safe? It feels rather high compared to what the value was for the XL2411Z - naturally that was 1080p, but still I just wish to make sure I am not doing something crazy.
3) Is overclocking the monitor like this likely to cause damage to it, or is it more the GPU I should be concerned about?

When I say that the MBR experience thus far has not been on par with the XL2411Z, I mean in terms of the ghosting I can see, and I get an occasional stutter which may be FPS related, I'm unsure. Any advice and information appreciated, thanks!

[falkentyne]

(11-07-2015 12:45 PM)ismithers Wrote:  I had the XL2411Z and just upgraded to this monitor as I wanted something larger and with a higher resolution. I have an AMD R9 280 which is unfortunately not free-sync enabled, so guess what is on my Christmas list, however my questions are related to MBR as compared to the XL2411Z I am finding it difficult to find a configuration I think looks reasonable/as good. This is over a Dual Link DVI connection.

I have used the CRU to create a custom resolution of 2560x1440 @ 120Hz. I have not adjusted the vertical/horizontal totals yet as I am worried about the clock speed. At present the pixel clock speed is at 480.40 MHz (naturally I had to use the AMD Clock Patcher to go over 300MHz).

I wish to ask:
1) I notice that when I use the custom resolution, my MBR menu in the OSD has two new options: Intensity & Area. What are these?
2) Is the pixel clock being at 480.40 MHz safe? It feels rather high compared to what the value was for the XL2411Z - naturally that was 1080p, but still I just wish to make sure I am not doing something crazy.
3) Is overclocking the monitor like this likely to cause damage to it, or is it more the GPU I should be concerned about?

When I say that the MBR experience thus far has not been on par with the XL2411Z, I mean in terms of the ghosting I can see, and I get an occasional stutter which may be FPS related, I'm unsure. Any advice and information appreciated, thanks!

That monitor is made for displayport. You should be using a displayport cable for it, as it's a displayport 1.2 monitor (which can go up to 680 MHz at 8 bits per channel color). The R9 280x is also DP 1.2 as far as I know. DVI and VGA are just for compatibility reasons, plus you can't use 2560x1440@144hz over DVI...it's impossible. And 120hz is not easy to get reliably over DVI at that resolution...the pixel clock is just too high.

The TDMS limit for DVI is around 450 mhz. Some monitors can go higher but you often get issues on many screens, depending on the scaler and chips.

That being said, you can go as far as you want as long as you don't get image corruption.

If you need a displayport cable ,

https://www.amazon.com/dp/B0098HVZBE/?tag=mtests-20#ad

This is a VESA certified cable which will 100% work without issues. Note: VESA owns displayport.

About motion blur reduction:
http://forums.blurbusters.com/viewtopic....2&start=20

The XL2730Z does not respond to vertical total tweaks for calculating crosstalk reduction. The debug menu shows the VT is applied, but it is ignored as far as how the scaler deals with strobing. The previous Z series and XL2430T would calculate crosstalk based on the vertical total range; increasing VT from 1133 (100hz) / 1144 (120hz) to 1497-1502 (anything in this 6 point range that does not cause frameskipping errors or pulsating backlight) will lower strobe crosstalk by 25% compared to no VT tweak at all. ( I explained on the forums exactly what the VT does to the scaler). Even though the XL2730Z will accept a VT As high as 1849, it will still have the same crosstalk as 1449 VT, as Bishi showed.

The crosstalk on XL2730Z (the amount you get on the screen compared to total screen size) is identical to XL2411Z *WITHOUT* VT tweaks. Callsignvega got the XL2730Z and he said even though the blur reduction brightness is much higher than ULMB Gsync monitors, the crosstalk was just too high.

You can lower ghosting by about 50% (not crosstalk, AMA ghosting) by enabling blur reduction and setting AMA to high afterwards. This works on XL2720Z easily. It works on XL2730Z but it's much harder to do. One person on overclock.net managed to do it but he couldn't do it a second time

[ismithers]

(11-07-2015 01:21 PM)falkentyne Wrote:  That monitor is made for displayport. You should be using a displayport cable for it, as it's a displayport 1.2 monitor (which can go up to 680 MHz at 8 bits per channel color). The R9 280x is also DP 1.2 as far as I know. DVI and VGA are just for compatibility reasons, plus you can't use 2560x1440@144hz over DVI...it's impossible. And 120hz is not easy to get reliably over DVI at that resolution...the pixel clock is just too high.

I actually tried using a DP cable from one my other monitors, and I got a constant message about their being no cable connected. I will try again later on today.

(11-07-2015 01:21 PM)falkentyne Wrote:  This is a VESA certified cable which will 100% work without issues. Note: VESA owns displayport.

Thanks. How do I confirm if my GPU is an R9 280 or an R9 280X? Additionally, I am in the market for something which supports Free-Sync, is the R9 390X a good bet? (The R9 390 appears to have a single DP which won't work, as I have 2 4K monitors I use for work purposes either side of my gaming monitor, and they require DP).

(11-07-2015 01:21 PM)falkentyne Wrote:  The crosstalk on XL2730Z (the amount you get on the screen compared to total screen size) is identical to XL2411Z *WITHOUT* VT tweaks. Callsignvega got the XL2730Z and he said even though the blur reduction brightness is much higher than ULMB Gsync monitors, the crosstalk was just too high.

If I am following correctly - there is nothing to be done - is this monitor just not very good then?

When I enabled Blur Reduction and depending on what refresh rate I am at, I can see two more options appear in that menu: Intensity and Area - what are these?

(11-07-2015 01:21 PM)falkentyne Wrote:  You can lower ghosting by about 50% (not crosstalk, AMA ghosting) by enabling blur reduction and setting AMA to high afterwards. This works on XL2720Z easily. It works on XL2730Z but it's much harder to do. One person on overclock.net managed to do it but he couldn't do it a second time

AMA to High or Premium? It sounds like I am getting crosstalk, though I am unsure what the visual difference between crosstalk and ghosting would be, won't they both show a partial image during movement?

Thanks for the information.

[falkentyne]

280x is a rebadged 7970 ghz edition.
280 is as far as I know, a 7950.

Crosstalk is a very thick double or triple image effect caused by the LCD panel being caught inbetween pixel transitions when strobing the backlight. It's basically caught inbetween frames. Unless you adjust the "Strobe phase" (this has been renamed to Area in the XL2730Z), crosstalk will always be worst at the bottom of the screen. This is because even though the entire backlight is strobed at once, refreshes are done from top to bottom in LCD panels. This is why input lag tests always show the top of the screen having a faster response time (less input lag) than the bottom of the screen. Since the bottom refreshes after the top, when strobing the backlight, the strobe gets completed before the bottom has finished the refresh. So this causes an image of frames caught between one refresh and the next refresh. That is called strobe crosstalk. Strobing turns the backlight on and off once per refresh; the duration that the backlight remains off is "Intensity", aka Strobe duty. It's reversed in the XL2730Z compared to the older blur reduction monitors, but basically, at a high strobe duty (more blur reduction effect=dimmer screen), during a strobe cycle, the backlight remains off for a longer period than it remains on. The on/off total cycle is the same duration in time, but the backlight is off longer than it is on.

When you lower the intensity, the backlight is on longer than it is off= less blur reduction effect, even though the total duration is still the same per refresh.

The problem is, the duration is going to be *faster* than the refresh is. Let's say you are at 120hz. Simple example. 120hz is 8.3 milliseconds of frame time. (1000 divided by refresh rate= milliseconds). 1000 / 120=8.3. Easy enough right?

Now remember the panel pixel response time is different from the refresh time. Let's say the panel has 3.7ms of pixel response time at the top of the screen and 14.3ms at the bottom of the screen.

So we strobe the backlight once per refresh. The refresh is 8.3 milliseconds.

As you can see the top of the screen will complete the pixel response EASILY during the refresh time (3.7ms vs 8.3ms)= NO strobe crosstalk.

the bottom however has a slower response time.
14.3ms response time at 8.3ms FRAME Time.
The strobe finishes, but the bottom hasn't finished the pixel transitions yet. You have an incomplete frame. As you can see. by simple math, you will see that the bottom is caught between the previous frame transition and the current frame transition. So you get two frames superimposed on each other. that's your crosstalk.

At 144hz, the frame time (refresh rate) is even FASTER than 120hz, so logically, you will have even MORE crosstalk (a larger crosstalk zone) at the bottom than at 120hz.

If the XL2730Z were capable of single strobing at 60hz (the XL2720Z is, the XL2730Z is not), you would notice that the crosstalk would be half the size at 60hz than at 120hz. Very self explanatory...60hz is 16.7ms frame time. Since the input lag is also going to rise, the total panel response time also goes up, but the panel can finish pixel transitions of far more of the screen at the slower refresh rate=less crosstalk.


So...what does the AREA setting do?

Simple. It changes *WHEN* the strobe begins and ends on the screen during the refresh, so the crosstalk position is moved up or down. It's basically moving the entire strobe to happen "earlier" or "later" in a set point in time, relative to the refresh itself. While Area is a simple name for "crosstalk area", if you look up the dictionary definition of PHASE, it tells you a lot more about what is going on. By changing the strobe PHASE, you are changing WHEN a strobe begins and ends (when the backlight is turned on or off) during the refresh period. In effect, you are changing the SYNC of the strobe to the refresh itself. I think this makes sense when you think about it.

Using a strobe phase (AREA) of 100 will give you one frame (1000 divided by refresh rate) of LOWER input lag than a strobe phase of 000, but you will have even more crosstalk at the bottom of the screen with a strobe phase of 100 than a strobe phase of 000. If the bottom of the screen is covered by a game HUD, like FPS game, and you can't see the crosstalk, strobe phase 100 (AREA=100) will give you the lowest input lag. You may wonder why this is the case. Well think about it for a minute.

The default strobe phase of 000 has an input lag of 1 frame HIGHER than strobe phase 100. This would only make sense if the strobe sync phase were strobing during the PREVIOUS frame at strobe phase 000 (meaning starting and ending the strobe mostly during the previous refresh) than at strobe phase 100 (the current refresh). And sure enough that's exactly what is going on. So you will have less crosstalk at the bottom of the screen but 1 frame of higher input lag at strobe phase (area) 000 ,and 1 frame faster (lower) input lag at phase (are) 100, but more crosstalk.

To demonstrate this, watch the position of the vertical red bar and the UFO's on this link and change the AREA from 0 to 100.

http://www.testufo.com/#test=photo&photo...&height=-1

-----------------------------
The previous blur reduction monitors (XL2720Z, XL2420Z, XL2430T, etc) allowed increasing the "vertical blanking interval" (Vertical total) via changing the VT from the default, to 1497-1502 (anything in this 6 point range) which lowered strobe crosstalk by 25%, because it gave the panel even more time to complete pixel transitions during each strobe. It basically made the entire strobe 'longer', if that makes sense. The XL2730Z does not respond to VT changes for strobe crosstalk anymore.

When you are not using blur reduction, you don't get any of this "Crosstalk" because the pixels are always on, so you see a completely uniform image top to bottom. It's just the input lag/response time will be slower at the bottom than at the top (although this is not exactly something you are going to notice in a game).

Ghosting is a completely different thing. Ghosting is from overdrive/voltages from pixels not finishing their color transitions, which isn't directly related to strobing itself. You will get ghosting whether or not you are using blur reduction. Just blur reduction makes ghosting more obvious since the blur is removed. There is a way to force an "AMA Low" mode when using blur reduction but I don't know how it's set on the XL2730Z. You're supposed to set AMA To high AFTER enabling blur reduction for this to work, but there may be something else involved that was different than the XL2720Z, so I can't help with this.

[ismithers]

Thanks for all that information. As a minor aside, when checking out the UFO tests, this monitor never seems to sync at 120Hz, only at 60Hz. So the tests all look fairly terrible anyway.

At present I have it running in 1080p @ 120Hz as the quality of life feels much better from it.

[falkentyne]

(11-08-2015 01:15 AM)ismithers Wrote:  Thanks for all that information. As a minor aside, when checking out the UFO tests, this monitor never seems to sync at 120Hz, only at 60Hz. So the tests all look fairly terrible anyway.

At present I have it running in 1080p @ 120Hz as the quality of life feels much better from it.

Use Google chrome for testUFO tests.

Internet explorer won't vsync higher than 105hz!
It will sync at 100hz, but the XL2730Z will NOT strobe correctly at 100hz (only the XL2720Z and older Z series will do that). Benq can't fix this with a firmware update (I asked them about it).

[ismithers]

(11-08-2015 01:17 AM)falkentyne Wrote:  Use Google chrome for testUFO tests.

Yeah I do, I have used the UFO Tests a bit with my XL2411Z. So have BenQ just released a dud monitor then? Like, what is the take-home information from this. The monitor won't ever be usable at 120Hz with MBR on, as it will crosstalk like crazy?

Thinking about approaching BenQ and asking them for a downgrade now. I thought this monitor would be good.

[falkentyne]

(11-08-2015 01:51 AM)ismithers Wrote:  

(11-08-2015 01:17 AM)falkentyne Wrote:  Use Google chrome for testUFO tests.

Yeah I do, I have used the UFO Tests a bit with my XL2411Z. So have BenQ just released a dud monitor then? Like, what is the take-home information from this. The monitor won't ever be usable at 120Hz with MBR on, as it will crosstalk like crazy?

Thinking about approaching BenQ and asking them for a downgrade now. I thought this monitor would be good.

it has nothing to do with that.
ULMB has the same crosstalk at 120hz.

Lightboost used accelerated scanout. You know ToastyX was the one who made the strobelight program for lightboost. Lightboost used the equivalent of "Vertical total 1497-1502" on Lightboost monitors to accelerate the scanout (vertical blanking period increased) to lower crosstalk. Benq blur reduction allowed this due to a firmware "bug". The VT would use the same type of effect as Lightboost mode but Benq admitted this was an unintended "bug" with the firmware and the monitor scaler that was exploited on blurbusters.

XL2730Z uses a new scaler so the VT tweaks don't work anymore.

Do you still have your XL2411Z?
You can see exactly what the crosstalk is on XL2730Z on your XL2411Z by creating a custom display scaled resolution.

2560x1440
Front porch 48, 3
Sync width 32, 5
Horizontal total: 2641
vertical total: 1502
Refresh rate: 100hz.

Then you can run your XL2411Z at 2560x1440@100hz and see the crosstalk. Yes the VT Tweak is active (VT 1502) but notice the resolution increase CANCELS the effect of the VT tweak!

120hz won't work over DVI; pixel clock exceeds DVI limitations and scaler limits for XL2411z.
It get an image over displayport but there is too much image corruption (ToastyX said its a scaler limitation; same artifacts happen on some Qinx panels when trying to run 2560x1440@120hz, but that can be fixed on Qinx by lowering vertical total to <1460. Only benq firmware bug allows this to work and VT can't go below 1497.

[ismithers]

(11-08-2015 02:05 AM)falkentyne Wrote:  Do you still have your XL2411Z?

No I upgrade to this monitor and replaced the XL2411Z.

(11-08-2015 02:05 AM)falkentyne Wrote:  120hz won't work over DVI; pixel clock exceeds DVI limitations and scaler limits for XL2411z.

Just to clarify, you mean 120Hz @ 1440p? (Because I had (on the XL2411Z) and have (on the XL2730Z) 120Hz @ 1080p over Dual Link DVI working fine. Just when testing with the UFO site, it only syncs at 60Hz which is weird. I'll try using the CRU to set a custom resolution and see if there is any difference, not sure how the UFO site divines the update speed from the monitor, so perhaps there is a missing connection somewhere.

[falkentyne]

(11-08-2015 02:53 AM)ismithers Wrote:  

(11-08-2015 02:05 AM)falkentyne Wrote:  Do you still have your XL2411Z?

No I upgrade to this monitor and replaced the XL2411Z.

(11-08-2015 02:05 AM)falkentyne Wrote:  120hz won't work over DVI; pixel clock exceeds DVI limitations and scaler limits for XL2411z.

Just to clarify, you mean 120Hz @ 1440p? (Because I had (on the XL2411Z) and have (on the XL2730Z) 120Hz @ 1080p over Dual Link DVI working fine. Just when testing with the UFO site, it only syncs at 60Hz which is weird. I'll try using the CRU to set a custom resolution and see if there is any difference, not sure how the UFO site divines the update speed from the monitor, so perhaps there is a missing connection somewhere.

Yes I've run a 1080p monitor at 1440p through "firmware bugs"
Ignore the OSD refresh rate. The OSD reports the strobe pulse widths timings based on what it thinks is proper for the current Vertical total and it switches to 60hz backlight pulse widths (for strobing) whenever the VT is run out of specification.