topic Re: Iris Xe - Best way to connect 3 monitors in Graphics

Iris Xe - Best way to connect 3 monitors

snoflake1118 — Wed, 08 Jan 2025 03:18:33 GMT

Currently I am using a laptop with an Intel HD 620, connected to a dock via USB C and it will only allow me to connect 2 monitors, resolution at 1920x1080. I am looking at purchasing a desktop with an Iris XE graphics card. Will I be able to connect 3 monitors at this resolution and if so, what is the best way to do that on a desktop (with no USB C port)?

Re: Iris Xe - Best way to connect 3 monitors

n_scott_pearson — Wed, 08 Jan 2025 04:07:17 GMT

If you have a USB dock, this would explain why you could not connect three monitors. If both USB and DisplayPort are in use downstream - and this is the case with a USB dock since it contains both USB and MST Hubs - only half the cable's bandwidth is available for DisplayPort. With DisplayPort 1.2, this barely leaves enough bandwidth for two 2K monitors. Now, if you had a device that only provided a 3-port MST Hub (i.e. no USB support at all), regardless of whether DP or HDMI ports, you would have had the cable's complete bandwidth and three 2K monitors would have been possible.
For your future system, first of all, you need a USB 4 dock - or better, a Thunderbolt 4 dock. The answer then will depend upon the motherboard. It will provide the connector(s) for the iGFX engine's ports. These may be standalone (DP and/or HDMI) ports and/or provided via UBC-C port(s) - which may be USB with DisplayPort Alt Mode and/or full Thunderbolt 3/4/5. That's a Lotta possibilities.
Clear as mud?
...S

Re: Iris Xe - Best way to connect 3 monitors

snoflake1118 — Wed, 08 Jan 2025 04:36:20 GMT

I'll have to read that a couple times to digest it. I'm in the tech industry but video and audio have always been super confusing to me 😭

BUT, let me add this - the dock has 2 HDMI ports and a Display port. On my work laptop, I can connect all 3 (identical monitors with both HDMI and DisplayPorts) and it works fine. Just doesn't work on my old as hell personal laptop (I can get pics on all 3 but resolution is super low on one). Which is why I assume the issue is the video card capability. So my plan is to update my PC but I don't really need it to be mobile so I figured I'd get more bang with a desktop. But the one I'm looking at doesn't have a USB-C port. So I wasn't sure if I could just get some type of adapter that would allow me to connect the dock from USB-C to USB- A? Or maybe some type of HDMI splitter for the monitors? But also I'm not sure how to check if the video card is capable of UHD on 3 monitors. Hope that all makes sense.

Re: Iris Xe - Best way to connect 3 monitors

n_scott_pearson — Fri, 10 Jan 2025 03:33:39 GMT

Well, I say the same thing, but a few things have stuck in my head along the way. Being an oldster, my UIs were mostly text-based. What few GUIs I developed were pretty rudimentary.

The difference between your work laptop and your personal laptop is the throughput capabilities of the DisplayPort interfaces of each processor, as well as the throughput capabilities of the USB interfaces of each motherboard. That is, depending upon whether your processor supports, for example, DisplayPort 1.2 vs. DisplayPort 1.4 vs DisplayPort 2.0, and whether your USB-C port supports, for example, USB 3.1 vs. USB 3.2 gen1 vs. USB 3.2 gen2 vs. USB 4.

The USB-C port offers two transmission 'channels' (for lack of a better name). Half of the DisplayPort channel's transmission capability is physically assigned to each of the USB transmission channels. If USB device communication is also supported by the dock (which is usually the case), one USB transmission channel is assigned to USB communication and one - instead of two - is assigned to the DisplayPort channel. This means that only half of the DisplayPort's transmission capability is available. In the case of most older processors, where only DisplayPort 1.2 is available, this is a huge problem. It means that, for example, instead of the port supporting a 4K monitor at 60Hz, it can only support this 4K monitor at 30Hz. In your case, this means only two 2K monitors can be supported fully (if the third monitor works at all, it is at a very low resolution) or multiple monitors are run at a lower frequency (30Hz or less). In the case of a more-modern processor, where the DisplayPort transmission capability is much higher, losing one of the USB transmission channels, while it does cut the throughout in half, this may still be sufficient to support all three monitors (as you saw with your work laptop). If they were 4K monitors, on the other hand, all bets would be off.

Understand that this is an oldster software guy explaining this. Maybe someone like @MUC can explain it better.

In your Desktop PC case, if there is a USB-C port supporting DisplayPort ALT mode, it will need to be provided by the motherboard that you choose. You can get PCIe cards that add a USB-C port, but this port will not have access to any of the processor's DisplayPort channels and thus cannot support DisplayPort ALT mode.

...S

EDIT: If you are purchasing a latest gen system (i.e. nothing too down-rev.), you are usually going to get that USB-C port. I didn't talk about the differences that happen when using a Thunderbolt dock on a Thunderbolt USB-C port, as this is way more complicated. Suffice it to say, way better solution - but way more expensive, both in rarity (and thus premium cost) of motherboards with Thunderbolt support as well as the cost of the Thunderbolt dock itself. Here's an example of a motherboard with Thunderbolt 4 support: https://www.newegg.com/p/N82E16813119695.

Re: Iris Xe - Best way to connect 3 monitors

MUC — Thu, 09 Jan 2025 14:27:48 GMT

If you no longer need to use a laptop as a PC, an Intel/ASUS NUC is the easiest solution, e.g.:

https://www.amazon.com/-/de/dp/B0DK96FHCD?th=1

This is the possible connection scheme for monitors:

ASUS > Support > FAQ > Multiple Displays for NUC 12 Pro

Cable examples to connect from Thunderbolt/USB Type-C to full size DisplayPort:

Re: Iris Xe - Best way to connect 3 monitors

snoflake1118 — Thu, 09 Jan 2025 19:51:06 GMT

Thank you for taking the time to explain all that - it helps a LOT! (and makes sense)

Re: Iris Xe - Best way to connect 3 monitors

snoflake1118 — Thu, 09 Jan 2025 19:52:56 GMT

Thanks so much for all this info! This all helps me understand what I need so much better 😊 (Also, that's a great PC option. I love ASUS and want something small form factor and not too expensive but robust)

Re: Iris Xe - Best way to connect 3 monitors

n_scott_pearson — Sat, 11 Jan 2025 00:39:38 GMT

I thought of another issue. Your older laptop's iGFX engine can only support a maximum of three monitors. If the internal display in the laptop is active, then a maximum of two external monitors can be supported. Your work laptop's iGFX engine, on the other hand, has the ability to support four monitors, meaning that, when the internal display is active, you can still support three external monitors. Bottom line, you have two issues limiting the number of external displays and the resolution and frequencies they can be used at.

I started to say something else the other day and then never finished it. USB is an alternative for adding an external display (or two); you can use an external USB GFX engine. While these would be lower performance displays (read: no gaming), but they would at least work. Here are some examples: 2x 4K@60Hz US$48, 2x 2K@60Hz US$37.

[EDIT: Just want to add that you can use a USB GFX engine regardless of how many monitors you have connected to the iGFX (or dGFX) engine. For example, you could connect two monitors to your dock and two monitors to one of these USB GFX engines and have a total of four external monitors and five displays total counting the laptop's display.]

...S