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Comment by digitalsushi | Hacker News Reader

Hi folks. I am not a hardware nerd at heart. It appears this 'iris' GPU will not be able to do 4k display. Does anyone confirm?

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Iris (such like the one in 13" rMBP) can't, Iris Pro (15" rMBP) can.

The HDMI has "Support for 4096-by-2160 resolution at 24Hz" - http://store.apple.com/us/buy-mac/mac-mini

Still only 1080p at 60Hz

Tech specs suggest both the Intel Iris and Intel HD Graphics 5000 models have the same support for 4K:

https://www.apple.com/mac-mini/specs/

It better be able to do 5K, since the Thunderbolt will inevitably be upgraded to the same screen the new Retina iMac comes with...

It won't because the bandwidth of TB2 cannot transfer the amount of data needed for a 5K display. The new Retina iMacs can get away with it because it can interface with the graphics output directly.

Hmmmm my math can be wrong but I don't think you are correct:

5120x2880 = 14745600 pixels

14745600pixels x 3 colours, 1 byte each = 44236800 bytes

44236800/1024/1024 = 42.19MB each frame

42.19MB per frame x 60 frames a second = 2531.25MB.

TB2 has a bandwidth of 20Gbps = 2560MB/s

So yeah, theoretically TB2 has enough bandwidth. But it's a very tight fit.

Displayport (and HDMI) have a 2 bit ECC overhead for every 8 bits transmitted, so effective bandwidth of DP 1.2 is 17.28 Gbit/s. Additionally, the timing adds additional overhead, so the required bandwidth is actually 22.18 Gbit/s for 24bpp 60Hz 5120x2880

I don't know the actual answer, but it may be that the display actually expects 32bpp, in which case it would be over the limit by a considerable amount.

The above calculation was for 32bpp:

3 colors * 1 byte * (8 bits/byte) = 32 bits

I am sorry,but no it wasn't. 3*8 is 24 not 32. But in any case I don't think the display requires 32 bits, alpha is not necessary.

Thanks for the clarification. fwiw, I knew that alpha wasn't necessary, but vaguely remembered that DisplayPort might support displays that expected the entire 32 bit word to be sent. Looking at the specs, I don't see that. But it does show that DisplayPort supports 16 bits per component, or 48bpp.

FYI, Wikipedia's section on DisplayPort lists the resolution of 5120x2880 x 24bpp @ 60Hz as requiring 22.18 Gb/sec of bandwidth, see http://en.wikipedia.org/wiki/DisplayPort#Specifications

Even if the GPU does, DisplayPort 1.2 doesn't support 5K displays.

According to Intel site, looks like it can do 4k.

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