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Using 240Hz monitor via Thunderbolt

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Using 240Hz monitor via Thunderbolt

Postby Spyro » 27 Feb 2018, 11:11

I have bought an ACER Predator XB272 (27", 1080p, 240Hz, G-SYNC, ULMB).

When connecting it to my laptop's (CLEVO P377SM-A, GeForce GTX 980M, Windows 10) Thunderbolt port, using an Accell's VESA certified MiniDisplayPort to DisplayPort cable, it doesn't work at all ("no signal"). It works on HDMI tho.

I have also tested the monitor on a desktop computer (GeForce GTX 660, Windows 7) using the cable that comes with the monitor (DisplayPort to DisplayPort) and it works (capped at 200Hz, probably limited by the quality of the cable).

Any ideas on how to use this monitor via the Thunderbolt like if I were using a MiniDisplayPort? I thought Thunderbolt was compatible with MiniDisplayPort, why it does not work at all?
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Re: Using 240Hz monitor via Thunderbolt

Postby Chief Blur Buster » 27 Feb 2018, 11:53

Technically, it should work sinc 1080p 240Hz is the same bandwidth as 4K 60Hz but there are many teething pains with Thunderbolt as a display connection standard for gaming monitors.

This is a "new technology" issue that I haven't had experienced yet.

I suggest looking for the "Why can't I use my 4K 60Hz monitor?" Instructions (seen elsewhere on Google) and trying those tweaks.

Also try contacting the manufacturers too as well, firmware/driver upgrades relating to the port, etc.

If you find a fix, please post here since others will want to know!
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Re: Using 240Hz monitor via Thunderbolt

Postby Spyro » 27 Feb 2018, 17:13

Refresh rate is irrelevant, it doesn't work at all when connected with a MiniDP to DP cable, shows "No signal" in screen. The laptop detects that something is connected tho, coz it applies the multimonitor settings.

I have done a number of different tests and now I know the problem. Tests I have done:
- Connect the laptop to the monitor using HDMI: It works.
- Connect the laptop to the monitor using a MiniDisplayPort to DisplayPort cable: Does not work.
- Connect the laptop to a different monitor (ASUS VG248QE) using the same MiniDisplayPort to DisplayPort cable: It works.
- Connect a desktop PC to the monitor using a DisplayPort to DisplayPort cable: It works.

The problem is: this monitor works when connected to a DisplayPort but not when connected to a MiniDisplayPort, I have no idea why, it's the most obscure thing I have ever seen.

I'm returning it tomorrow, there's no way to fix it. :x
Last edited by Spyro on 27 Feb 2018, 18:31, edited 1 time in total.
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Re: Using 240Hz monitor via Thunderbolt

Postby Chief Blur Buster » 27 Feb 2018, 17:19

I was not talking about refresh rate but bandwidth specs available --

There's likely a specification incompatibility somewhere. The adaptor need to be 100% fully compatible with 4K60 in order to be 100% compatible with 1080p240Hz. I've seen adaptor issues. But it could be the monitor.

Do you have a 2nd MiniDisplayPort adaptor (of a totally different brand) available to try?
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Re: Using 240Hz monitor via Thunderbolt

Postby Spyro » 27 Feb 2018, 17:58

I have tried a bunch of Mini DisplayPort to DisplayPort cables, but all of them were crap except the this last one from Accell that I have tried, which supports up to 4K 60Hz and it's VESA certified.

The only cable left that I could try it's the Club3D CAC-1115 which supports up to 8K 60Hz and it's the absolute best MiniDP to DP cable in the market as far as I know.
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Re: Using 240Hz monitor via Thunderbolt

Postby Spyro » 14 Mar 2018, 07:50

Got a new unit and still doesn't work, interesting.
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Re: Using 240Hz monitor via Thunderbolt

Postby Chief Blur Buster » 14 Mar 2018, 09:17

What new unit -- a different model of a monitor? Or a different model of adaptor?

The last time people had problems with a "Better Than 60Hz" monitor on BlurBusters traced it to their adaptor. Might not be your issue but worth mentioning. Thunderbolt 3 has a lot of teething problems in standardization. More than 50% of adaptors fail at the dotclocks brandwidths of a 240Hz monitor, so it's an area of huge concern.

One thing I learned: At lower bandwidths, 4K60Hz works via 2-tiling (two channels) -- basically those adaptors work at 4K30Hz by default until it treats your screen as two side-by-side 60Hz monitors (using both channels), but newer adaptors can do 4K60Hz single-channel (all 8K60 capable ones can do 4K60 single-channel, and thus, 1080p240 too). That's the kind of adaptor you need for 1080p240Hz. This can get complicated, eh...

Essentially, you need 600Mhz 24-bit (8bpc) pixel clock bandwidth successfully making through a single channel through all adaptor conversions, for it to work. But there may be other protocol gotchas (e.g. flags) that trips everything up.

How many adaptors have you tried? What are their brand names?
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Re: Using 240Hz monitor via Thunderbolt

Postby Spyro » 16 Mar 2018, 13:07

Chief Blur Buster wrote:What new unit -- a different model of a monitor? Or a different model of adaptor?

Got a new unit of the same 240Hz monitor (ACER Predator XB272).

Chief Blur Buster wrote:How many adaptors have you tried? What are their brand names?

The adaptors I have tried are the Club3D CAC-1115 and the Accell UltraAV. Before these 2 good ones I tried a bunch of lower quality ones that I already had. I also tried the DisplayPort to DisplayPort cable that comes with the monitor (which worked on a DisplayPort Win7 desktop PC @ 200Hz) with the StarTech DisplayPort to Mini-DisplayPort converter.

Chief Blur Buster wrote:The last time people had problems with a "Better Than 60Hz" monitor on BlurBusters traced it to their adaptor. Might not be your issue but worth mentioning. Thunderbolt 3 has a lot of teething problems in standardization. More than 50% of adaptors fail at the dotclocks brandwidths of a 240Hz monitor, so it's an area of huge concern.

My laptop has Thunderbolt 2 (theorically 100% compatible with Mini-DisplayPort 1.2). I wanted to try the monitor on a native Mini-DisplayPort but couldn't find any friend that owned a machine with it. This new unit has the same problem as the previous, doesn't even work at 60Hz while connected to the Mini-DisplayPort/Thunderbolt 2, only via HDMI.

Chief Blur Buster wrote:One thing I learned: At lower bandwidths, 4K60Hz works via 2-tiling (two channels) -- basically those adaptors work at 4K30Hz by default until it treats your screen as two side-by-side 60Hz monitors (using both channels), but newer adaptors can do 4K60Hz single-channel (all 8K60 capable ones can do 4K60 single-channel, and thus, 1080p240 too). That's the kind of adaptor you need for 1080p240Hz. This can get complicated, eh...

Interesting... the Club3D CAC-1115 is 8k60Hz tho.

Chief Blur Buster wrote:Essentially, you need 600Mhz 24-bit (8bpc) pixel clock bandwidth successfully making through a single channel through all adaptor conversions, for it to work. But there may be other protocol gotchas (e.g. flags) that trips everything up.

I will definitely discard in the future any machine/graphics card with Mini-DisplayPort or Thunderbolt instead of DisplayPort.
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