Framework Laptop 13 Ryzen 7840U bottom right expansion port: DisplayPort 2.1 4K 120Hz?

Framework Laptop 13
1

Hi all, about the Framework Laptop 13 with AMD Ryzen 7840U: from time to time, I’d like to connect up to three 4K displays at 120Hz (Eve / Dough Spectrum One) for some multitasking with web browsing, productivity apps, and light coding in Linux. Lid closed most likely. Doable?

Looking at the AMD’s Ryzen 7 7840U specs and this block diagram (attached below):

amd-mobile-fp8
amd-mobile-fp81500×446 58.4 KB

I see that the display engine has:

  • 3x DP 2.1 40Gbps / HDMI 48Gbps
  • 1x eDP 1.4 32Gbps

That’s a total of 4 displays possible, which matches up with AMD’s specs. IIUC, is the display routing something like this?

  • eDP 1.4 → internal panel
  • DP 2.1 → top left slot (or USB4)
  • DP 2.1 → top right slot (or USB4)
  • DP 2.1 → bottom right slot (or USB 3.2)

After seeing the expansion card functionality knowledge base article for this model, and the product spec page for the AMD Framework 13, I read “Display” and “USB 3.2/DP”, I wasn’t sure whether it was DisplayPort 1.4 or 2.1. Now that I’ve seen the block diagram for this chip, I just want to make sure I understood correctly:

  • Does the bottom right port have the full (40Gbps) DisplayPort 2.1 capability when a display is connected? Can I get that third 4k 120 Hz display?
  • If so, do I need to actually use the DisplayPort Expansion Card in that slot to achieve this, or can I use a USB-C expansion card and pass it through?
  • Any interactions with the USB 3.2-only “bottom left” expansion slot?
  • Any other considerations for my use case?

Thanks, all the best!
B

2

Framework has not officially stated the version of DisplayPort. DisplayPort 1.4 (32.4 Gbps) has been confirmed to be working, but I have not seen anyone attempt to go higher.

However theoretically it could work as the bottom right port is equipped with the Analogix ANX7493 retimer (a chip responsible for repeating signals to help maintain signal integrity over long cables). The ANX7493 advertises support for “DisplayPort up to UHBR10 @ 10Gbps” so it seems likely to be supported (DisplayPort has 4 lanes, so 4 lanes each at 10 Gbps = 40 Gbps).

The back ports however are equipped with Kandou KB8002 retimers. The datasheet for those retimers mentions support for “Display Port™ 1.4a LTTPR non-transparent and transparent up to HBR3 (8.1 Gbit/s)”. So the back ports may be limited to DisplayPort 1.4a due to retimer limitations.

Yes, regardless of if the ports are capable of DisplayPort 2.1 40 Gbps or if they are limited to DisplayPort 1.4a.

DisplayPort 1.4a has enough bandwidth to run 4k 120 Hz 24-bit color with no compression if Reduced Blanking V2 is used.

Blanking is bandwidth where display data isn’t sent (mostly a holdover from old displays that needed that for compatibility reasons) and with modern displays it is almost always fine to tinker in driver settings and enable Reduced Blanking V2 (which reduces the blanking, therefore making more efficient use of bandwidth).

DisplayPort 1.4a also supports DSC (Display Stream Compression). DSC is considered a visually lossless compression algorithm, which means it technically reduces quality but not by enough for humans to detect.

With a single DisplayPort 1.4a port there is theoretically enough bandwidth to drive three DSC-compressed 4k 120 Hz displays using a single DisplayPort 1.4a port, although I am not aware of any MST hubs (chips that share a DisplayPort signal among multiple monitors) that advertise that level of capabilities.

The DisplayPort Expansion Card is ultimately just a USB-C to DisplayPort adapter. Any other USB-C to DisplayPort adapter can achieve the same thing.

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Great, thanks for the detail Kyle. I’m glad I didn’t overestimate too far, but I would have had you not answered. I’m glad to hear that there will be enough overlap in the ports. What interesting opposites of chips… A USB4 40Gb + DP1.4a 32.4Gb and a USB3.2 20Gb + DP2.0 40Gb. I assume there is a cost savings somewhere there in one or both. Or perhaps not much choice.

Anyway, it would be good to have better listings for the port capabilities on the various models. It really makes a difference.

Best,
B

4

Yes, Framework has so far failed in providing good specs for the ports. And what the GPU supports is very distinct from what a product using that chip supports. Intel 13th gen for example has supported UHBR10, UHBR20 and USB3 20Gbps from the start. But the ReTimer chips Framework uses do not, hence none of that functionality is available on ports.

Does your display even support UHBR10 speeds? And even if it does, it will most likely not need UHBR10 speeds to achieve 4K120. Most displays do that with only HBR3 speeds or less.

And that would be irrelevant / is known. The “version of DisplayPort” refers to a PDF. And that is determined 99% by the GPU. And nothing on the board will likely have an impact on that. So if you quote any DP version, it will be 2.1 as stated by AMD for that iGPU. But the speed is independent of that. AMD themselves only support the lowest of the 3 speeds that have been added between 1.4 and 2.1. And if the board manufacturer did not want to expose the full speed or not every part of the chain is ready for UHBR10 speeds, then you are simply not getting that. Without any impact to other protocol features.

The speed may be throttled, but that does not take away that the port was designed for DP 2.1 and supports all other features that are part of that spec and do not come down to connection speed. And the ReTimer will have nothing to say about that.

Is that important? Which monitor actually achieves 4K120 that way? Is there any? Most simply rely on DSC with HBR3 or less.

No. At worst, if it is not qualified for those speeds it could block it (Framework does not say, they sold the DP expansion card shortly stating DP 2.1, but then removed that again. Unclear what the top-speed is those have been confirmed / designed for). The USB-C expansion cards we know are designed and working for USB4 Gen 3, which is exactly as fast and demanding as UHBR20, so those are definitely good enough for up to UHBR20. Since the DP expansion card is simple, it might also be. But only FW knows.

And knowing what the ReTimer chips can do is one thing. Even if the chip can do UHBR10, does not necessarily mean that the board can and the chip has been configured to actually do it. And it should have been easy for Framework to just list the non-USB4 DP output at faster DP speeds than the USB4 ports if it did support the full speed. But they rather removed all mentions of speed or DP capabilities. At this point, only testing with a UHBR10-capable sink will tell, because Framework seems invested in not providing clear specifications for ports and or expansion cards.

AMD stating 8K60 support for their iGPU is imprecise. It does not guarantee that all ports could do that at the same time. For example previous AMD iGPUs listed 4x 4k60 as max. Even though they could support way more for a single display. Intel has more detailed specs that go like 4x 4k60 or 1x 8K60 guaranteed. So there might be a tradeoff at some point, where you cannot drive every display at max. bandwidth at the same time due to overall memory bandwidth limitations. 4K120 is nowhere near the bandwidth limit for a single of those ports or the display pipes, and my guess is 3x 4K120 will probably work, but it could very easily be outside of what AMD officially guarantees, just like it would be for past and current Intel iGPUs. And you could run into issues that way. Or even a straight up message from the driver of “you have exceeded iGPU capabilities, deactivate some displays or reduce their bandwidth to enable further ones”.

5

This might help the discussions:
I got this from FW support some time ago:

DisplayPort Expansion card
DisplayPort (1st Gen) Expansion Card - Supports DisplayPort 1.4 for monitors up to 8k 60Hz resolution Supports up to 4 monitors at 4k 60Hz resolution (using 4 cards) 50% post-consumer-recycled aluminum 30% post-consumer-recycled plastic
DisplayPort (2nd Gen) Expansion Card - The DisplayPort (2nd Gen) Expansion Card has optimized firmware to reduce system power consumption, improving laptop battery life. Passes through DP Alt Mode directly from the Mainboard, enabling support for the maximum DisplayPort version and monitor resolution supported by the processor.
External monitor support on the Framework Laptop ​

The Framework Laptop 16 has 6 slots for Expansion Cards, and it is fully compatible with all Framework Expansion Cards available for the Framework Laptop 13. However, the functionality of each slot varies. Please refer to the image below

Expansion Card Slot functionality on Framework Laptop 16

We hope this information helps. Should there be anything else, do not hesitate to contact us. We are always here to assist.

6

Sadly, the DP 1.4 part is technically wrong.
Also 8K60 or 4 displays at 4K60 is BS. Those might be limitations of a particular GPU (and look, it matches Intel specs for 11th-13th gen iGPUs), but it is not applicable to a port or cable.
Saying it this way also immediately disqualifies whoever said that from having the technical knowledge of knowing what speed the DP card is limited to. We can only infer from it, that it can do at least HBR3 speeds. and nothing else.

This is a typical first-level customer support answer of people that are not technical and try to summarize for a customer what they can guarantee end-to-end. If the question is, what DP speed does the DP expansion card support, this is an absolute non-answer. Also it is what was already linked from the knowledge base.

That is one of Frameworks problems, that they have modularity and common components across multiple different systems. And they try to give specs that apply to a specific mainboard with components that are shared across all of them.
If you wanted to be precise and focus on modularity you would need to state the technical capabilities of each component. And then, you could summarize that for customers convenience for specific common combinations of components for the customers that do not understand or do not want to deal with the various different properties and how they interact to find the bottleneck of a specific combination of components.

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@Ray519
My question to FW support was about a FW16. I added the FW13 URLs myself to the post above.
I made the inference that 3 of the expansion slots support DP, so I could in theory plug 3 monitors in and get whatever resolution the GPU can do. I only have 2 monitors, so I have only tried with 2 so far, and it works, but my monitors are not 4k, they are less.

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And my point was that listing monitor specs with the DP expansion card is fundamentally technically wrong. Because that assertion only can apply to the combination of mainboard and expansion card. It could be a valid statement in context like:
“the FW16 AMD 7040 mainboards with a DP expansion card in any of the DP-output capable slot officially supports up to”…

And then, they would still be wrong, because the 7040 iGPUs are not DP 1.4 (of the FW mainboards this would only be true for the 11th and 12th gen. Nothing else).
They might be right on the 4x4K60 or 1x8K60. AMD does not make that stuff public, so I cannot double check. It will certainly be in the wheel-house. But since it is a carbon copy of old Intel specs (11th through 13th gen) and the DP version is wrong (its also irrelevant and should not be stated. so if you state it it better not be wrong on top of that), I have my doubts that those are even official quotes from AMD themselves.

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@Ray519
I agree with you. The FW documentation is not necessarily accurate or unambiguous.
I guess the only way to be sure is for someone to actually test it with 3 or 4 4k 120Hz screens.

10

My guess is that the monitors’ DP ports are HBR3. The net capability of the Framework 13 as implemented was more a curiosity at that point. Really, I just want to know for sure what the true limits are and how close I am skirting, all things considered.

This was the other thing I was hinting at, I guess. It’s not an absolute deal breaker to fail at getting 120Hz on all displays. I would likely only notice on my center display where I put my focus and things move more. I just like how 120Hz feels, and my wondering got me in a more confused place.

That I will be doing soon!

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One minor point:
The ports are DP alt-mode and not DP+ alt-mode.

12

Yeah. Most GPUs are not precise on that. Because it would also get extremely technical. I think Nvidia has the most precise info on when the number of screens reduces.

But for iGPUs, memory bandwidth also varies. Earlier Intel GPUs (like 6-8th gen) could do like 3x 4K60 but only if fast memory and not single channel etc was used. Nowadays memory should be fast enough to easily do the 4 x 4K60 Intel and AMD guarantee, but above that it might very well depend on DDR4 / 5 and what speed again etc. Or it might just take more bandwidth away from the CPU cores or lead to stuttering under rare circumstances. But there seems to be a lot of headroom. And Intel for example pretty much implies that each of their pipelines can do ~ 4K120+ (and they fuse 2 for as high as 8K60). So if you cannot actually run 4 of those, that would be more because the memory is not fast enough to run the system and those screens continuously. And it is just a question if the driver will block you from going that far preemptively or will just let you do it and the system might then stutter and be unnaturally slow). And on AMD FW it is slightly harder to even stress the iGPU that far, because you have 1 less external DP output. And you quickly run into port-bandwidth limitations when trying to drive multiple displays of that bandwidth through a single port (although each USB4 port should easily support 2x 4K120 if done right).

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Yes. Although that 3-4 screen test will test the iGPU. That should be pretty much identical for all 7040 CPUs with similar memory and driver versions.

UHBR10 DP speeds on the non-USB4 DP output is not needed to drive those kind of displays. That could be a separate test. There just are not that many displays or USB-C hubs that use UHBR10 or higher speeds.

And although it is extremely likely that the DP expansion card will just do UHBR10 (its very close in speed to HBR3 and essentially the DP expansion card is a 3cm extension cable with a PCB) or even faster, that would be a third test. And even if it had failed official signal integrity tests for those speeds, it would probably be close enough that many GPUs would run it at higher speeds and maybe only downgrade the speed later after a few transmission errors.
Similar with many shorter USB cables and USB3 10Gbps or even DP and adapters.

Remember, DP only requires signals from source to sink have a minimum quality. So it is the combination of adapter / extension cable and actual cable that needs to have good enough quality. A USB-C DP adapter not being qualified for higher speeds might not be able to guarantee it working with every DP compliant cable, but it might still work correctly with shorter cables or cables that are better than the minimum required quality. DP has no chips like USB-C eMarkers. The GPUs just try the speed they want and see if test-patterns arrive at the sink in tact. If not, they reduce speed or ignore wire-pairs.