Hobneb
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HDMI/DisplayPort/Thunderbolt Questions

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The Precision 7720 with P5000 video card is specced at DisplayPort 1.4, HDMI 1.4 and Thunderbolt 3. I know that you can get adapters to go from DP to HDMI or Thunderbolt to DP and HDMI though. If I have an application that requires HDMI 2.0 for example, can you get it from the Thunderbolt 3 port or the DisplayPort or is there an underlying limit to HDMI 1.4 in the processor itself? I'm having a hard time understanding the various capabilities.

Wayne

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jphughan
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RE: HDMI/DisplayPort/Thunderbolt Questions

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Hey Wayne,

First, be aware that just because a GPU supports something, it does not mean that it was implemented in the rest of the system.  There are GPUs in PCs that support far more displays than the system does because the OEM chose not to wire as many display outputs as possible to the GPU, for example.

Second, Thunderbolt 3 to the best of my knowledge only carries DisplayPort 1.2, even if the GPU supports DisplayPort 1.4, and it also only carries DisplayPort; it will not natively output HDMI, DVI, or VGA.

In terms of HDMI 2.0, it depends on what you're trying to do there. If you need 4K @ 60 Hz, that's achievable.  If you need HDR, that is NOT at the moment; no laptop on the market that I'm aware of supports HDR at this time, although it's also such a problem with Windows and GPU drivers right now that it's hardly worth it, but that's another story.

But if you only need 4K @ 60 Hz and only from a single display, the simplest way to achieve that is with a USB-C (not Thunderbolt 3) to HDMI 2.0 adapter.  USB Type-C when used exclusively for video (i.e. not being required to carry USB traffic at the same time, as it would be with a dock) has the bandwidth of a full DisplayPort 1.2 output, which is enough bandwidth for 4K @ 60 Hz.

If you need two 4K @ 60 Hz displays simultaneously, you would need a Thunderbolt 3 to Dual DisplayPort adapter and then a pair of active DisplayPort to HDMI adapters that support 4K @ 60 Hz.  The "active" part means that the adapter itself can convert a DisplayPort signal to HDMI internally.  Most DP to HDMI adapters on the market are passive, relying on the host to fall back to native HDMI signaling on its DisplayPort output, but Thunderbolt 3 can't do that, and I don't believe any of the TB3 to Dual DP adapters on the market do either.  Be aware however that those adapters typically require your Thunderbolt firmware to be at least NVM18.  To check this on your system, open Thunderbolt Software, right-click the tray icon, click Settings, then click Details.  Dell has dragged their feet on Thunderbolt firmware updates for some systems, so this is a potential pitfall.

Lastly, there's also the TB16 dock, but reading over the manual, its HDMI output is limited to 4K @ 30 Hz, so it's probably 1.4.  The DP and MiniDP outputs each support 4K @ 60 Hz and you can run both of them at that resolution simultaneously, so you might be able to buy a DP to HDMI and a MiniDP to HDMI adapter to connect your HDMI 2.0 devices to that dock via those ports (and the dock does NOT require active adapters on its DisplayPort outputs) but I haven't tested that.

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jphughan
5 Tungsten

RE: HDMI/DisplayPort/Thunderbolt Questions

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Hey Wayne,

First, be aware that just because a GPU supports something, it does not mean that it was implemented in the rest of the system.  There are GPUs in PCs that support far more displays than the system does because the OEM chose not to wire as many display outputs as possible to the GPU, for example.

Second, Thunderbolt 3 to the best of my knowledge only carries DisplayPort 1.2, even if the GPU supports DisplayPort 1.4, and it also only carries DisplayPort; it will not natively output HDMI, DVI, or VGA.

In terms of HDMI 2.0, it depends on what you're trying to do there. If you need 4K @ 60 Hz, that's achievable.  If you need HDR, that is NOT at the moment; no laptop on the market that I'm aware of supports HDR at this time, although it's also such a problem with Windows and GPU drivers right now that it's hardly worth it, but that's another story.

But if you only need 4K @ 60 Hz and only from a single display, the simplest way to achieve that is with a USB-C (not Thunderbolt 3) to HDMI 2.0 adapter.  USB Type-C when used exclusively for video (i.e. not being required to carry USB traffic at the same time, as it would be with a dock) has the bandwidth of a full DisplayPort 1.2 output, which is enough bandwidth for 4K @ 60 Hz.

If you need two 4K @ 60 Hz displays simultaneously, you would need a Thunderbolt 3 to Dual DisplayPort adapter and then a pair of active DisplayPort to HDMI adapters that support 4K @ 60 Hz.  The "active" part means that the adapter itself can convert a DisplayPort signal to HDMI internally.  Most DP to HDMI adapters on the market are passive, relying on the host to fall back to native HDMI signaling on its DisplayPort output, but Thunderbolt 3 can't do that, and I don't believe any of the TB3 to Dual DP adapters on the market do either.  Be aware however that those adapters typically require your Thunderbolt firmware to be at least NVM18.  To check this on your system, open Thunderbolt Software, right-click the tray icon, click Settings, then click Details.  Dell has dragged their feet on Thunderbolt firmware updates for some systems, so this is a potential pitfall.

Lastly, there's also the TB16 dock, but reading over the manual, its HDMI output is limited to 4K @ 30 Hz, so it's probably 1.4.  The DP and MiniDP outputs each support 4K @ 60 Hz and you can run both of them at that resolution simultaneously, so you might be able to buy a DP to HDMI and a MiniDP to HDMI adapter to connect your HDMI 2.0 devices to that dock via those ports (and the dock does NOT require active adapters on its DisplayPort outputs) but I haven't tested that.

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Hobneb
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RE: HDMI/DisplayPort/Thunderbolt Questions

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Thanks! That helps a lot. Will have to look into that dock. I assume then that since Dell advertises DP 1.4 on the 7720 that would then be via the mini DP port. I want to dip my toe into VR (initially as a possible quality of life enhancement for the disabled/elderly with limited mobility) and want to be able to look intelligently at what’s compatible.

Initially I was just wanting a high end graphics WS for image processing. Hadn’t even thought of VR, but then looked into it when I saw the 7720 advertised as VR Ready. Now cautiously excited about the potential. Funny sometimes when you’re heading down one road you find an interesting unexpected detour!

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jphughan
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RE: HDMI/DisplayPort/Thunderbolt Questions

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If the system ITSELF is advertised as supporting DisplayPort 1.4, then yes it's a good bet that it does.  I thought you just looked at the specs of the GPU from NVIDIA's site.  DisplayPort 1.4 actually DOES support HDR, but if you need an HDMI adapter, that could become an issue.  In theory, any adapter that supports HDMI 2.0 should be able to pass 4K @ 60 Hz with HDR, but for an active adapter, there may some limitation on the adapter's DisplayPort input side that might make that a problem, and I'm not sure whether DisplayPort 1.4 can fall back to HDMI 2.0 with HDR natively in order to support a passive adapter.  Hazards of being on the cutting edge!

All that said, I suspect you're right that DP 1.4 support only applies to the MiniDP output on the system itself.  One of the issues with Thunderbolt 3 is that despite supporting a seemingly huge 40 Gbps throughput, when you have dual display outputs as TB3 does, even DisplayPort 1.2 interfaces when doubled up can consume up to 32 Gbps in a 2x 4K @ 60 Hz setup -- and that's before considering the bandwidth required to run any USB 3.1 Gen 2 and PCI Express devices you may have attached.

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