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Active cooling appears to be necessary only for driving a 3840x2160 screen at 60Hz.
The maximum resolution supported by the new rMB wil be equivalent to 1440x900 (HiDPI 2x 2880x1800 resolution scaled down to the 2304x1440 grid of pixels of the screen). It will not need active cooling and supposedly Broadwell Core M should support it at 60Hz.

Yes. But will the core M support 1920x1200 scaled using a 3rd party app without active cooling. That's the question.
 
Active cooling appears to be necessary only for driving a 3840x2160 screen at 60Hz.
The maximum resolution supported by the new rMB wil be equivalent to 1440x900 (HiDPI 2x 2880x1800 resolution scaled down to the 2304x1440 grid of pixels of the screen). It will not need active cooling and supposedly Broadwell Core M should support it at 60Hz.

But Apple's spec sheet itself specifies 3840x2160. So, then, it must be 30Hz? Is that really bad at 30Hz?
 
I wonder if one could just put a laptop cooler on it and be able to drive it at 60hz.
 
I wonder if one could just put a laptop cooler on it and be able to drive it at 60hz.

Now that would really get the "rMB haters" going!:

You could buy a fan/cooler accessory to cool your new rMB so that it could work at 4K at 60Hz like rMBP machines.
 
Yes. But will the core M support 1920x1200 scaled using a 3rd party app without active cooling. That's the question.
Running at 1920x1200 upscaled to 2304x1440 would work I suppose (but on a 12" screen, I don't really think it would be much usable).
 
It can't, it's not possible.

USB-C has max 10 Gbits/sec bandwidth.

4k 60Hz 4:4:4 needs around 12 Gbits/sec

bit_per_channel = 8
– num_channels = 3 (RGB)
– resolution = 3840 * 2160
– 60Hz = 60 times per second
– bandwidth = 3840 * 2160 * 8 * 3 * 60
– bandwidth 4k@60Hz = 11.94 Gbits/sec

Case closed

- It's really quite interesting how many uninformed people on these forums make this claim. It's nonsense.
DisplayPort 1.2 is natively supported through the connection, providing more than enough bandwidth for 4K.

Also, the USB 3.1 on the rMB is Gen 1, so it actually only supports 5 Gbps.

Cool username, by the way...
 
- It's really quite interesting how many uninformed people on these forums make this claim. It's nonsense.
DisplayPort 1.2 is natively supported through the connection, providing more than enough bandwidth for 4K.

Also, the USB 3.1 on the rMB is Gen 1, so it actually only supports 5 Gbps.

Cool username, by the way...

So are you saying it is possible with a display port dongle
 
- It's really quite interesting how many uninformed people on these forums make this claim. It's nonsense.
DisplayPort 1.2 is natively supported through the connection, providing more than enough bandwidth for 4K.

Also, the USB 3.1 on the rMB is Gen 1, so it actually only supports 5 Gbps.

Cool username, by the way...

Does DisplayPort 1.2 specify whether 30Hz and 60Hz are both supported?
 
Yes it would be. Display Port bandwidth isn't the only factor in system's ability to support 4K at 60Hz.

I'm kind of excited about this. I only need to convince my boss at work to buy a 4K monitor for me. I pay for my own computer so I think I could get him yo pay for that if it really works.
 
So are you saying it is possible with a display port dongle

- I am saying that the connection itself supports it. Whether the computer as a whole will be able to handle 4K at 60 Hz is another matter. I doubt it will due to a lack of sufficient cooling of the Core M processor.
 
- I am saying that the connection itself supports it. Whether the computer as a whole will be able to handle 4K at 60 Hz is another matter. I doubt it will due to a lack of sufficient cooling of the Core M processor.

I am uncertain what you meant by 'coding' of the Core M processor. Are you saying that it is a software thing?
 
I am uncertain what you meant by 'coding' of the Core M processor. Are you saying that it is a software thing?

He wrote Cooling, not Coding.

I am pretty sure it will be 30Hz. This will be perfectly fine for what the machine is intended for, i.e. Office work and light load photo and movie editing (as in iMovie and the Photos app). Would be very frustrating for high end 3D games though. But then again, the Macbook is not going to be running into this point as the bottleneck anyway. The GPU will be the limiting factor here.

DP 1.2 native through the connection, like he said, means that the port itself supports full DP 1.2 capabilities, but I am pretty sure 60Hz won't be supported...at least not until the Skylake Core M processor.

However, if you run the machine in mirroring mode, and not as a second display, and shut the lid, then it probably COULD do 60Hz.

We'll have to wait and see. Still a couple weeks until the reviews start pouring out when the embargo is lifted.
 
He wrote Cooling, not Coding.

I am pretty sure it will be 30Hz. This will be perfectly fine for what the machine is intended for, i.e. Office work and light load photo and movie editing (as in iMovie and the Photos app). Would be very frustrating for high end 3D games though. But then again, the Macbook is not going to be running into this point as the bottleneck anyway. The GPU will be the limiting factor here.

DP 1.2 native through the connection, like he said, means that the port itself supports full DP 1.2 capabilities, but I am pretty sure 60Hz won't be supported...at least not until the Skylake Core M processor.

However, if you run the machine in mirroring mode, and not as a second display, and shut the lid, then it probably COULD do 60Hz.

We'll have to wait and see. Still a couple weeks until the reviews start pouring out when the embargo is lifted.

My bad. I should have had my reading glasses on!
 
I suspect that if the rMB can only drive 4K at 30Hz, because of thermal constraints (60Hz requires active cooling), then the M Core processor will have little processing power (generating heat) available for anything else.

This, if you are using a 4K monitor with your rMB, your turbo mode power will probably be much shorter than usual before the thermal limit is reached.
 
I suspect that if the rMB can only drive 4K at 30Hz, because of thermal constraints (60Hz requires active cooling), then the M Core processor will have little processing power (generating heat) available for anything else.

This, if you are using a 4K monitor with your rMB, your turbo mode power will probably be much shorter than usual before the thermal limit is reached.

- We have our answer. Apple now officially lists support for 4K at 60Hz on the Retina MacBook, though there currently aren't any cables available to actually do it...

Apple said:
With OS X Yosemite v10.10.3, most single-stream 4K (3840x2160) displays are supported at 60Hz operation on the following Mac computers:
...
MacBook (Retina, 12-inch, Early 2015)
 
I just tried Google's USB-C to DisplayPort adapter - max I could do is 2560 in SST mode @ 60hz
 
- We have our answer. Apple now officially lists support for 4K at 60Hz on the Retina MacBook, though there currently aren't any cables available to actually do it...

Unfortunately Apple updated their article to explicitly remove Retina Macbook from the 4k 60hz list. Perhaps they'll re-add it when their own DisplayPort Multiport adapter ships (if such a thing will eventually exist...) But for now it's a no-go.
 
Unfortunately Apple updated their article to explicitly remove Retina Macbook from the 4k 60hz list. Perhaps they'll re-add it when their own DisplayPort Multiport adapter ships (if such a thing will eventually exist...) But for now it's a no-go.

DisplayPort adapter isn't the issue here. The GPU and lack of active cooling is the reason why rMB cannot support 4K@60Hz.
 
DisplayPort adapter isn't the issue here. The GPU and lack of active cooling is the reason why rMB cannot support 4K@60Hz.

Not necessarily. Active cooling can also be recommended when pushing beyond the default TDP- which Apple certainly does. So it could be that the new Macbooks could handle the necessary heat dissipation in their design. Or perhaps they already use that extra headroom and they can't spare any more.

Either way, I'll bet Skylake Macbook's have it sorted out...
 
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