4k 60Hz output?

Aboo said:

Hi Folks,

Anyone try connecting their retina MacBook 284K display running at 60 Hz? I had read some discussions about the USB C output being potentially limited to 30Hz but this was all based on the available data prior to the launch of this machine. Now that there are plenty of retina MacBooks out in the wild, I was just curious to see if anyone has been successful in running their MBs with a 4k external display. Overall, how is the performance with this setup?

Thanks!

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According to the Apple website, it's max 30hz for 4K.

From memory, I think USB-C has a throughput of 10Gbps, while the thunderbolt 2 ports needed 20Gbps to drive 4K at 60hz. So I'm not saying it can't be done, but I'd say if you want to drive it at 60hz, get a different Mac.

we want someone from this forum who actually tested it.

Kiwi 99 said:

According to the Apple website, it's max 30hz for 4K.

From memory, I think USB-C has a throughput of 10Gbps, while the thunderbolt 2 ports needed 20Gbps to drive 4K at 60hz. So I'm not saying it can't be done, but I'd say if you want to drive it at 60hz, get a different Mac.

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USB 3.1 Gen 1 has a 5Gps bandwidth. It has already been tested and confirmed that 4k @ 60Hz is not possible with the rMB. Sorry I don't have any links at the moment, but it is confined to 30Hz refresh rate for 4k.

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junkw said:

we want someone from this forum who actually tested it.

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There are several threads with people running 4k monitors already, just go on those threads and ask them!

Here's Ars Technica's confirmation that it can't do 60Hz:
http://arstechnica.com/apple/2015/04/the-2015-macbook-previews-a-future-thats-not-quite-here/3/

Kiwi 99 said:

From memory, I think USB-C has a throughput of 10Gbps, while the thunderbolt 2 ports needed 20Gbps to drive 4K at 60hz. So I'm not saying it can't be done, but I'd say if you want to drive it at 60hz, get a different Mac.

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- It's 5 Gbps on the USB part. But USB-C is capable of native DisplayPort, which Apple has implemented in version 1.2 (which is around 17 Gbps), so the connection itself can do 60Hz. The limiting factor is the Core M.

JTToft said:

Here's Ars Technica's confirmation that it can't do 60Hz:
http://arstechnica.com/apple/2015/04/the-2015-macbook-previews-a-future-thats-not-quite-here/3/


- It's 5 Gbps on the USB part. But USB-C is capable of native DisplayPort, which Apple has implemented in version 1.2 (which is around 17 Gbps), so the connection itself can do 60Hz. The limiting factor is the Core M.

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Exactly correct, thanks for posting the link I was too lazy to provide.

To be more specific, it is the the Broadwell Core M chipset that is limiting factor as it only supports the USB 3.1 Gen 1 5Gbps - all other current model Macbooks' CPU chipsets support TB 2 now, as well as native DP 1.2 I believe (correct me if I'm wrong there) so the new MB is the odd one out that can't do 4k at 60Hz. It's not a knock on the CPU or GPU, but rather on the chipset Intel decided to package with Broadwell Core M. Skylake is said to be bringing USB 3.1 Gen 2 and TB 3 support on the Skylake Core M chipset.