GPU advice needed: what's the most budget AMD GPU with 2+ DisplayPort 1.2+ to drive 5k display?  

 

protium
(@protium)
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June 18, 2018 10:40 pm  

Hi, i am currently shopping for a GPU to use as a "video adapter" between thunderbolt 1 and dual display ports. I have a 1st gen retina macbook pro 15 with 650M dGPU, and it has thunderbolt 1 ports

it appears that AMD card might work easier with this system, so i am preferring that.
in addition, i managed to temporarily use an akitio node with 1080 Ti and an apple thunderbolt 1/2/3 adapter, but it was very difficult to set up. I had it working for one instance with 5k@60Hz, then i can no longer get it working again after a reboot.

RX 470/480/570/580 seem to mostly have at least 2 DPs, but they are still somewhat expensive. Any one knows cheaper alternative here? I am not interested in graphics performance, just to drive a 5k display for web browsing, email checking and PDF reading. 

Thanks!


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Haoshiro
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June 19, 2018 1:26 pm  

Have you looked into the RX560? I do not think most models have two DP but I believe they have DP1.4 which can drive 8K@60 iirc.

I picked up a used one on eBay for less than $100 a few months ago for my daughter running in an eGPU setup (a GDC Beast over PCMCIA). I do not have a 5K monitor or 1st Gen rMBP to test with for you, though.

death to self


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Yukikaze
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June 19, 2018 3:30 pm  
Posted by: Haoshiro

Have you looked into the RX560? I do not think most models have two DP but I believe they have DP1.4 which can drive 8K@60 iirc.

If the @protium has a monitor that needs two DP1.2 inputs for 5K (first gen 5K monitors, from before DP1.3/DP1.4 were a thing), then having a single DP1.4 port won't help - Unless @protium is also willing to buy a DP1.4 MST hub, which is going to be expensive and relatively rare.

I personally used an R9 Fury to drive my Z27q (at least on the Win10 side of things, as I am not running a Mac), which leads me to believe you don't need an RX/Vega card to pull this off, and an older R9 card should work just fine, as long as it has a pair of DP1.2 ports. The scripts that enable the eGPUs on Macs have support all the way back to the HD78XX/79XXX series.

@protium - Which enclosure are you running for this? Is it the Node you mention? Or should the suggested solution include the enclosure?

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Sky11
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June 19, 2018 9:07 pm  

RX560 is not meant to drive that kind of displays, and besides, it is not supported for MacOS eGFX.
I would suggest you to look at RX570 as minimum for 5K panel.
Besides, RX570 is no longer expensive - ~$280


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joevt
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June 23, 2018 3:59 am  

I think macOS Nvidia drivers only support the Dell UP2715K 5K display (dual DisplayPort input), because the EDID vendor ID and product ID are hard coded in the driver. A patch exists for the LG UltraFine 5K display (dual DisplayPort over Thunderbolt 3 - requires a Dual DisplayPort input Thunderbolt 3 add-in card, but macOS won't enable PCIe tunneling on the add-in card so functions of the display requiring PCIe communication won't work: USB ports, audio, camera, brightness control). I suppose the patch could be changed to support other dual DisplayPort 5K displays like the Z27q. I don't know how well the patch works. It may need to be updated for each new driver version.

macOS AMD drivers have no problem with dual DisplayPort 5K displays (Thunderbolt 3 or not Thunderbolt 3) as AMD is used in all current Macs and the LG UltraFine 5K was made for Thunderbolt 3 Macs. I have a MacBook Pro 2015 with AMD Radeon R9 M370X 2 GB which can drive a Dell UP2715K at 5K with two DisplayPort cables directly, or two DisplayPort cables connected to a GC-ALPINE RIDGE Thunderbolt 3 add-in card to a StarTech Thunderbolt 3 to Dual DisplayPort adapter.

I don't know if macOS supports DisplayPort 1.3 or 1.4 displays. Probably not. All current Thunderbolt 2 or 3 ports only support DisplayPort 1.2. An eGPU won't be limited by the Thunderbolt port, so DisplayPort 1.3/1.4 should be possible. It depends on the drivers.

macOS doesn't support MST for display chaining. It supports MST for old 4K displays that use a separate stream for the left and right sides. This means MST hubs don't work. Do DisplayPort 1.4 MST hubs exist? If so, please link an example. I wonder if it can support multiple DisplayPort 1.2 displays that would exceed the bandwidth allowed by DisplayPort 1.2 MST hub.

Maybe Apple will make a new 5K Thunderbolt display to go with their new ?modular? Mac Pro. The new display would use the Titan Ridge JHL7440 to support DisplayPort 1.4 and Thunderbolt 3 for Thunderbolt computers and USB-C for non-Thunderbolt computers. It will either use DisplayPort 1.4 (making only 4K possible with older Macs) or dual DisplayPort 1.2 (making 5K not possible with USB-C connection). It might be possible to support both single and dual input modes. For example, with the existing LG UltraFine 5K display, the computer sees the dual DisplayPort 1.2, and can choose to output a single 4K signal or dual 2560x2880 signals. With the new 5K display, the computer could see dual DisplayPort 1.4 in Thunderbolt mode, and choose to output a single 4K signal (DisplayPort 1.2), single 5K signal (DisplayPort 1.4) or dual 2560x2880 signals (DisplayPort 1.2). In USB-C mode, the computer would see a single DisplayPort 1.4 and can output 5K (DisplayPort 1.4) or 4K (DisplayPort 1.2). Thus full compatibility with older Macs (DisplayPort 1.2) could be maintained while improving functionality on future Macs (DisplayPort 1.4).


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 chx
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June 26, 2018 10:28 am  
Posted by: joevt

I think macOS Nvidia drivers only support the Dell UP2715K 5K display (dual DisplayPort input), because the EDID vendor ID and product ID are hard coded in the driver.

If OP has that monitor then the Lenovo Graphics Dock is a $320 (Lenovo perks store, see /r/thinkpad wiki for details) enclosure + GPU in one which is very hard to beat price wise for this use case.


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