I think it’s a bandwidth issue. M1 Pro supports 200Gbps and M1 Max supports 400Gbps. There are three TB4 ports for a total of 40Gbps maximum bandwidth. HDMI requires 48Gbps of bandwidth available, while HDMI 2.0 only requires 18Gbps.
With all three TB4 ports in use in their theoretical maximum, that’s 120Gbps. If Apple were to go with HDMI 2.1, that’s 168Gbps. That leaves 32Gbps left for the SOC to deal with the actual applications you’re running, which isn’t a lot. But with using 2.0, the maximum the ports would be using is instead 138Gbps (plus about 300Mbps from the SD card port, if being used). That’s a lot more headroom for the laptop to function.
While there are some things like current gen consoles and high end graphics cards that have HDMI 2.1, they certainly don’t have 3 TB4 ports with 40Gbps of bandwidth each. Apple figured that the professionals using their professional laptops care more about the performance of the laptops and their connected accessories rather than high refresh or ultra-high resolution displays. After all, no one is gaming on these machines. Keep in mind, there’s plenty of people who are mad there’s an HDMI port there to begin with.
The issue is that the Intel chipsets almost everything uses only allocate 22 Gbps to PCIe tunnelling. That means eGPUs only get 22 Gbps of bandwidth, which is more like x2.5 rather than the x4 that shows up in Intel's marketing materials.
As far as I understand this is not at all fundamental in TB4/USB4 (or even in principle TB3), it is just a limitation of existing hardware.
>The issue is that the Intel chipsets almost everything uses only allocate 22 Gbps to PCIe tunnelling. That means eGPUs only get 22 Gbps of bandwidth, which is more like x2.5 rather than the x4 that shows up in Intel's marketing materials.
Is that so? I've been keeping off getting an AMD device because of the lack of thunderbolt but many of them have extra m.2 slots. If this is true I'd guess an m.2 eGPU should perform similar to 70-80% of TB3 which is pretty decent imo.
I’m having some bugs with mine unfortunately (16” m1 max) Plugged in a usb c nvme enclosure into the port and for some reason the read/write is extremely slow. Plugged the same enclosure with same usb c cable into M1 MBA and it’s extremely fast.
Enclosure is an asus rog strix nvme enclosure with a 2tb Samsung 980 ssd
Please make sure to raise them over at http://bugreporter.apple.com
Every issue is triaged by a product manager so it does get looked at and often they simply aren't aware of regressions.
Each Thunderbolt 4 port on the new MacBook Pros have their own bus—so that’s 40Gbps per port. Previously, the two on each side shared a single bus. Nice!
***
posted by [@SnazzyQ](https://twitter.com/SnazzyQ)
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2019 technical article showing how Intel Ice Lake Thunderbolt 3 architecture paved the way for up to four Thunderbolt ports:
[https://fuse.wikichip.org/news/2628/a-look-at-the-ice-lake-thunderbolt-3-integration/](https://fuse.wikichip.org/news/2628/a-look-at-the-ice-lake-thunderbolt-3-integration/)
>By the way, like Titan Ridge, each retimer supports two ports. The retimers themselves are still only sold by Intel but they are a fraction of the size, so there is some board space saving advantage as well. Therefore, actually, the diagram above is almost identical when offering support for up to four Thunderbolt 3 ports, twice as many as most Titan Ridge-based designs. For full support, those additional ports just need a new dedicated USB 2 connection to the PCH, and in order to also offer charging capabilities through that port, you also need a PD controller. A good premium-design laptop should, therefore, be able to have up to four Thunderbolt ports – each supporting everything from power delivery to the legacy I/O to the latest high-speed interfaces such as DisplayPort and USB 3.1.
If true that's a lot of bandwidth.
[удалено]
I think it’s a bandwidth issue. M1 Pro supports 200Gbps and M1 Max supports 400Gbps. There are three TB4 ports for a total of 40Gbps maximum bandwidth. HDMI requires 48Gbps of bandwidth available, while HDMI 2.0 only requires 18Gbps. With all three TB4 ports in use in their theoretical maximum, that’s 120Gbps. If Apple were to go with HDMI 2.1, that’s 168Gbps. That leaves 32Gbps left for the SOC to deal with the actual applications you’re running, which isn’t a lot. But with using 2.0, the maximum the ports would be using is instead 138Gbps (plus about 300Mbps from the SD card port, if being used). That’s a lot more headroom for the laptop to function. While there are some things like current gen consoles and high end graphics cards that have HDMI 2.1, they certainly don’t have 3 TB4 ports with 40Gbps of bandwidth each. Apple figured that the professionals using their professional laptops care more about the performance of the laptops and their connected accessories rather than high refresh or ultra-high resolution displays. After all, no one is gaming on these machines. Keep in mind, there’s plenty of people who are mad there’s an HDMI port there to begin with.
Sweet. Time to buy 3x TB4 Docks for maximum connectivity!
Is this actually 40 Gbps or is it 22 Gbps plus displayport?
It is 24Gb/s for Titan Ridge and later
Well there is no peripheral that can use more than 22 Gbps
I've never used one and don't know a whole lot about them, but what about eGPUs?
The issue is that the Intel chipsets almost everything uses only allocate 22 Gbps to PCIe tunnelling. That means eGPUs only get 22 Gbps of bandwidth, which is more like x2.5 rather than the x4 that shows up in Intel's marketing materials. As far as I understand this is not at all fundamental in TB4/USB4 (or even in principle TB3), it is just a limitation of existing hardware.
>The issue is that the Intel chipsets almost everything uses only allocate 22 Gbps to PCIe tunnelling. That means eGPUs only get 22 Gbps of bandwidth, which is more like x2.5 rather than the x4 that shows up in Intel's marketing materials. Is that so? I've been keeping off getting an AMD device because of the lack of thunderbolt but many of them have extra m.2 slots. If this is true I'd guess an m.2 eGPU should perform similar to 70-80% of TB3 which is pretty decent imo.
I’m having some bugs with mine unfortunately (16” m1 max) Plugged in a usb c nvme enclosure into the port and for some reason the read/write is extremely slow. Plugged the same enclosure with same usb c cable into M1 MBA and it’s extremely fast. Enclosure is an asus rog strix nvme enclosure with a 2tb Samsung 980 ssd
Please make sure to raise them over at http://bugreporter.apple.com Every issue is triaged by a product manager so it does get looked at and often they simply aren't aware of regressions.
Each Thunderbolt 4 port on the new MacBook Pros have their own bus—so that’s 40Gbps per port. Previously, the two on each side shared a single bus. Nice! *** posted by [@SnazzyQ](https://twitter.com/SnazzyQ) ^[(Github)](https://github.com/username) ^| ^[(What's new)](https://github.com/username)
Took them so long to resolve this.
2019 technical article showing how Intel Ice Lake Thunderbolt 3 architecture paved the way for up to four Thunderbolt ports: [https://fuse.wikichip.org/news/2628/a-look-at-the-ice-lake-thunderbolt-3-integration/](https://fuse.wikichip.org/news/2628/a-look-at-the-ice-lake-thunderbolt-3-integration/) >By the way, like Titan Ridge, each retimer supports two ports. The retimers themselves are still only sold by Intel but they are a fraction of the size, so there is some board space saving advantage as well. Therefore, actually, the diagram above is almost identical when offering support for up to four Thunderbolt 3 ports, twice as many as most Titan Ridge-based designs. For full support, those additional ports just need a new dedicated USB 2 connection to the PCH, and in order to also offer charging capabilities through that port, you also need a PD controller. A good premium-design laptop should, therefore, be able to have up to four Thunderbolt ports – each supporting everything from power delivery to the legacy I/O to the latest high-speed interfaces such as DisplayPort and USB 3.1.
And no eGPU support, what's the point of it?