m1 air 上外接了一个 u2720m 显示器盒盖使用,mac 系统信息里查看, 发现 usb 口 Speed: Up to 480 Mb/s
然后翻看了下 dell 显示器的说明书,
传输速度 SuperSpeed Hi-Speed Full speed 数据速率 最大功耗(每个端口) 5 Gbps 4.5 W 480 Mbps 2.5 W 12 Mbps 2.5 W
是不是理论上可以到 5 Gbps 的速率了,如何才能协商到 5G 的速率?
1
snsn 2022-08-18 20:20:48 +08:00
降低刷新率到 30HZ 试试
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2
Sketch 2022-08-18 21:01:17 +08:00
如果是用 USB-C 连接的话,可以调整 菜单->显示->USB-C 优先级 试一下
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3
czwstc 2022-08-18 21:12:11 +08:00 via iPhone
2720QM 上面,4K 60HZ 和 USB3.0 只能二选一
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4
Eagleyes 2022-08-18 21:12:31 +08:00
会不会是连接线的质量问题?我刚好有这个疑问。
除此之外,我记得,U2720QM 的 TYPE-C 优先级设置有“高分辨率”和“高数据速度”两个模式 M1 和 U2720QM 是支持 DP1.4 的 设置为“高数据速度模式”,可以解决速率异常问题,代价是,无法跑到 4k 60hz 10bit 。 设置为“高分辨率”,可以跑满 4k 60hz 10bit ,传输速率会有影响 |
6
i0QSJ901LBPIncf5 2022-08-18 22:58:48 +08:00
U2720QM 接 MBA M2, 速率优先模式, 显示器识别为: 2160P, 30-bit, USB 3.1
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7
Eagleyes 2022-08-18 23:01:44 +08:00
@mycs999 #5 我有看了一下,记错了,高速率模式也能跑到 4k60fps ,但是颜色位深只有 8bit ,
这个显示器是支持 10bit 的。在系统设置里看。8 位和 10 位色彩差别还是挺大的。鱼和熊掌不可兼得。 又或者说,dell 这个显示器省成本,在一些普通人不怎么用的地方缩水了 |
9
mycs999 OP @apo11o But as general background info, the way USB-C works (prior to USB4, which this display doesn't support) is that it has 4 high speed lanes. Each lane can be allocated to video or USB 3.x data (or Thunderbolt, but that isn't relevant here). A full DisplayPort interface requires 4 lanes. Running USB 3.x data requires 2 lanes, which means that if you want to run video and USB 3.x together, your video bandwidth gets cut in half. USB 2.0 flows over pins dedicated to that purpose within the USB-C connector.
When you select High Data Speed, the connection is configured to support 2 lanes of DisplayPort and 2 lanes for USB 3.x. High Resolution causes the display to set up the connection for 4 lanes of DisplayPort and USB 2.0 (using those dedicated pins). The M1 Mac Mini supports DisplayPort 1.4/HBR3 over USB-C. Half of a DP 1.4 interface is enough for 4K 60 Hz, but apparently not 4K 60 Hz HDR. Limiting your USB speeds to 2.0 frees up more bandwidth, which is apparently needed for HDR. If you had a system that only supported DisplayPort 1.2/HBR2 over USB-C, this option is even more important because in that case you have to run High Resolution even to get 4K 60 Hz, otherwise you'd be limited to 4K 30 Hz if you wanted USB 3.x. This setting also comes into play on QHD/1440p displays where when you have a DP 1.2 system, you can choose to have QHD 60 Hz plus USB 3.x or dual QHD 60 Hz (via daisy chaining) with USB 2.0. But macOS doesn't support DisplayPort daisy chaining. dell 论坛搜到的,好像 8 位和 10 位就差了 hdr 部分,感觉 hdr 平时真用不到,这个显示器的 hdr400 没啥用 |
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i0QSJ901LBPIncf5 2022-08-19 23:12:40 +08:00
@mycs999 macOS12.5.1, firmware M2T105, Smart HDR off. 是因为我把 HDR 关了的原因? 因为感觉开 HDR 色彩很假, 之前已经关了.
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