Acer Predator XR341CK/X34 34" Curved Gaming Screens with FreeSync and G-sync

Vega said:
Good review Baddass as always. Could you double check your math though on DP 1.2. I'm getting DP 1.2 with overhead removed can do 3440 x 1440 up to 145 Hz.

DP 1.2 should be able to do 3440 x 1440 at 144 Hz, but that doesn't mean the internal electronics like G-Sync can do it (1st gen G-Sync cannot do full DP 1.2), and of course the 3440 x 1440 screens have a serious panel speed issue.
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you can't remove the overhead..

you need to revisit your math.. DP 1.2 has just over 17Gbit/s of available bandwidth..
http://en.wikipedia.org/wiki/DisplayPort

DP 1.1 = High Bit Rate = 10.8 Gbit/s Raw = 8.64 Effective (video) (10.8 x .8)
DP 1.2 = High Bit Rate 2 (HBR2) = 21.6 Gbit Raw = 17.28 Effective (21.6 x .8)
DP 1.3 = High Bit Rate 3 (HBR3) = 32.4GBit Raw = 25.92 Gbit Effective (32.4 x .8)

What is RAW vs Effective you may ask..

RAW = the total available bandwidth , Effective = "real" bandwidth AFTER 8b/10b encoding is taken into account. ie the data seen is only 80% of the total sent.

You see, when data is sent over there are 10 bits total, for every 8 bits of information. The extra 2 bits are used for encoding and transmission. In laymans, think of these are the <1B--BEGIN HERE><DATA --- 8B><END HERE--1B> (yes yes I know is MUCH more than that.. :-) )

So for every 8 bits of "color" (data) this is sent in a 10 bit "package"..


Now lets look at how many pixels are needed for JUST one frame

3440 x 1440 = 4,953,600 Pixels

Take that and multiply by the desired FPS (limited by Hz).. ie 144 cycles per second

4,953,600 x 144 (FPS/Hz) = 713,318,400 pixels per sec !!!

Now remember we have 3 "colors" (RGB) aka channels.. EACH one sent in 10 bit packets..

713,318,400 x 3 (channels) x 10 bits (per channel) = 21399552000 of Video Data Rate

This comes to 21.40Gb/s of data, far exceeding the 17.28Gbit/s available.

Edit: Availabel resources:

https://www.amd.com/Documents/50279_AMD_FirePro_DisplayPort_1-2_WP.pdf
http://www.displayport.org/faq/
http://www.audioholics.com/hdtv-for...-standard-v1.0/displayportdvihdmicompared.gif
http://www.vesa.org/wp-content/uploads/2014/04/VESA_DSC-ETP200.pdf
 
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Phixsator said:
Im surprised to see that the gsync model of the acer is actually worse for wear than the freesync one.. Frame skipping is NOT a good thing.. Why cant you be better ACER... why?!?



I wouldnt get the Dell U3415w if gaming is the main thing you do.. i use to think it was awesome for gaming but as TFTCentral has highlighted in their review of it, it has some bad response times going from dark to bright. It is actually so bad that if you drag a browser window with OCUK 's forum in it the avatars would trails very clearly to the naked eye. Another example is grass in game with dark grounds under it will look like its shimmering or pulsing a bit(i suck at explaining the effect) when moving around. Dont get me wrong, its a pretty good monitor and im happy with mine but the second a proper one hits the market i will sell it..
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I dont notice it the avatar thing on my dell
 
@md_guy said:
you can't remove the overhead..

you need to revisit your math.. DP 1.2 has just over 17Gbit/s of available bandwidth..
http://en.wikipedia.org/wiki/DisplayPort

DP 1.1 = High Bit Rate = 10.8 Gbit/s Raw = 8.64 Effective (video) (10.8 x .8)
DP 1.2 = High Bit Rate 2 (HBR2) = 21.6 Gbit Raw = 17.28 Effective (21.6 x .8)
DP 1.3 = High Bit Rate 3 (HBR3) = 32.4GBit Raw = 25.92 Gbit Effective (32.4 x .8)

What is RAW vs Effective you may ask..

RAW = the total available bandwidth , Effective = "real" bandwidth AFTER 8b/10b encoding is taken into account. ie the data seen is only 80% of the total sent.

You see, when data is sent over there are 10 bits total, for every 8 bits of information. The extra 2 bits are used for encoding and transmission. In laymans, think of these are the <1B--BEGIN HERE><DATA --- 8B><END HERE--1B> (yes yes I know is MUCH more than that.. :-) )

So for every 8 bits of "color" (data) this is sent in a 10 bit "package"..


Now lets look at how many pixels are needed for JUST one frame

3440 x 1440 = 4,953,600 Pixels

Take that and multiply by the desired FPS (limited by Hz).. ie 144 cycles per second

4,953,600 x 144 (FPS/Hz) = 713,318,400 pixels per sec !!!

Now remember we have 3 "colors" (RGB) aka channels.. EACH one sent in 10 bit packets..

713,318,400 x 3 (channels) x 10 bits (per channel) = 21399552000 of Video Data Rate

This comes to 21.40Gb/s of data, far exceeding the 17.28Gbit/s available.

Edit: Availabel resources:

https://www.amd.com/Documents/50279_AMD_FirePro_DisplayPort_1-2_WP.pdf
http://www.displayport.org/faq/
http://www.audioholics.com/hdtv-for...-standard-v1.0/displayportdvihdmicompared.gif
http://www.vesa.org/wp-content/uploads/2014/04/VESA_DSC-ETP200.pdf
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Too bad your math is double tapping overhead. 8b/10b is with the overhead, so you can't try and fit a 8b/10b number (21.40) into a number with 8b/10b encoding overhead removed (17.28).

Perfect example is HDMI 2.0 which can run 4K @ 60 Hz just fine and has the following specs:

Maximum total TMDS throughput (Gbit/s) including 8b/10b overhead - 18
Maximum throughput (Gbit/s) with 8b/10b overhead removed - 14.4

3840x2160 = 8294400 x 60 = 497664000 x 3 = 1492992000 x 10 = 14.93 Gbit/s. Clearly that fits into 8b/10b overhead of 18 Gbit/s but over 8b/10b overhead removed - 14.4 Gbit/s.

The proper math for overhead removed:

3840x2160 = 8294400 x 60 = 497664000 x 3 = 1492992000 x 8 = 11.94 Gbit/s.


So once again, DP 1.2 can do 3440x1440 up to and including 145 Hz.
 
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Phixsator said:
Im surprised to see that the gsync model of the acer is actually worse for wear than the freesync one.. Frame skipping is NOT a good thing.. Why cant you be better ACER... why?!?
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The Gsync model wasn't tested. It's the Freesync model which seems to skip frames at 75hz refresh from an nvidia card
 
johnnystuff said:
I didn't get it: how many bits are sent 8 or 10? And at what point exactly does the overhead gets removed?
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video is sent in 10 bit "packages" (easiest way to think of it as).. and as Vega pointed out I did inadvertently double dip on the 8b/10b encoding however we also need to remember that Display Port carries much more than just video packets.. it must also carry audio, as well as secondary data and of course copy right protection (for both video and audio) and save room for the Aux channel.

Vesa did a presentation a few years back 2010-2011ish. Trying to find that link now.

Edit: http://www.vesa.org/wp-content/uploads/2011/01/ICCE-Presentation-on-VESA-DisplayPort.pdf

The overhead is not removed per say, it part of the transmission, it's only "removed" to show the effective video data available.
 
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Joe_Easy said:
If they can do gsync 3440 x 1440 IPS at more than 85hz (or 100hz as rumoured) then 3840x2160 (4K) IPS at 85hz must not be far behind
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Depends on your defintion of 'far'. Anything higher than 60Hz is currently outside the realms of Display Port 1.2 bandwidth @ 4K. There may be a teeny tiny bit of room before it hits the ceiling (5hz perhaps), but not enough for it to make THAT much difference. At 4K resolution, you can forget 85Hz+ for now, it's simply impossible. We will inevitably see faster 4K panels eventually, but not until DP 1.3 is out in the wild, and even then you'll need a new GPU with a DP 1.3 connection to run it.

If the X34 G-Sync hits 100Hz, that's pretty much the limit for DP 1.2 in terms of max resolution/max refresh until DP 1.3 comes out.
 
I can't believe I'm about to type this, but if they bring out a gsync version that can hit 85hz reliably, I might buy an Acer monitor. Buy an Acer monitor, just typing it again to see how it feels....

It feels wrong.
 
wunkley said:
I can't believe I'm about to type this, but if they bring out a gsync version that can hit 85hz reliably, I might buy an Acer monitor. Buy an Acer monitor, just typing it again to see how it feels....

It feels wrong.
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acer would have to pay me to use any product of theirs! :p

I really hope we see benq bring a version of this out, preferably both g and free sync too.
 
I do hope the 100Hz is correct, but I am very much discouraged by the fact this monitor is being made by Acer. I too would prefer to see BenQ release a model (or better yet Samsung or Dell, but that's not going to happen), but given the only other one that's on the horizon is the Asus 3800R (and even that's months away), I wouldn't hold my breath. If I were to get the Acer there's only place I'd consider buying it from due to their no quibble return policy (whom I won't mention but the savvy among us can probably guess). As for price, based on the one place it's currently available for pre-order at £960, we can expect it to be around that.
 
However tempting this is, and how ridiculous spending £900 on a monitor sounds, it's so tempting, but as the above posters, I wish it wasn't Acer.

After going through 3 B276HKs within a month, there would have to be a lot to tempt me in. Unfortunately, I think this is going to do it.
 
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