Max external monitor resolution; MBPr 13/15?

[Qwerty11]

I keep seeing different numbers. Could somebody lay down the truth?

 

[campyguy]

Hah, good one! I have two 15" units with dGPUs at my disposal, a mid-2012 rMBP and a late-2013 rMBP. With Dell P2715Q displays, my earlier unit shows 1440p as a max resolution and my later unit shows 2160p as a max resolution, both at a max of 60Hz, both over mDP>DP cables. There's no other real "answer" - Apple offers that my later rMBP isn't capable of 4k, but it is, and two displays to boot!

I'm finding that the "max resolution" is a function of the Mac's hardware, the Mac's software, the cable used, and what the display's EDID conveys to the Mac. Re the Mac's software - I had one Dell connected in Mavericks and Yosemite, and only a reconfiguration of my workspace led me to discover that my newer Mac could drive two 4k displays after 10.10.3 hit the interwebs, even through Apple doesn't acknowledge it (even though I let them know months ago!).

 

[Freyqq]

Late 2013 rmbp 15" with 750M and external P2415Q 4k monitor. I can confirm, I am driving it at 4k@60hz.

 

[Samuelsan2001]

It's fairly simple 4K for the 13 inch, 5K for the 15 inch using dual cables in the thunderbolt ports.

 

[snaky69]

I keep seeing different numbers. Could somebody lay down the truth?

You do know Apple has that question answered, black on white, straight on the product's webpage, right?

I'll be nice and quote it to you.

Dual display and video mirroring: Simultaneously supports full native resolution on the built-in display and up to 3840 by 2160 pixels on an external display, both at millions of colours

 

[campyguy]

You do know Apple has that question answered, black on white, straight on the product's webpage, right?

I know about that webpage! That's the one that doesn't list my rMBP as being capable of displaying 4K on an external monitor, and yet it's driving two Dell 27" 4k displays @60Hz along - at 4k - with the built-in display at full res. I notified Apple months ago, they've blown it off. So, I'm siding with the OP here...

 

[Samuelsan2001]

I know about that webpage! That's the one that doesn't list my rMBP as being capable of displaying 4K on an external monitor, and yet it's driving two Dell 27" 4k displays @60Hz along - at 4k - with the built-in display at full res. I notified Apple months ago, they've blown it off. So, I'm siding with the OP here...

From apples Tech spec page for the 2015 13" rMBP

• Intel Iris Graphics 6100

• Dual display and video mirroring: Simultaneously supports full native resolution on the built-in display and up to 3840 by 2160 pixels on up to two external displays, both at millions of colors.

Thunderbolt digital video output

• Native Mini DisplayPort output
• DVI, VGA, dual-link DVI, and HDMI output supported using Mini DisplayPort adapters (sold separately)

HDMI video output

• Support for 1080p resolution at up to 60Hz
• Support for 3840-by-2160 resolution at 30Hz
• Support for 4096-by-2160 resolution at 24Hz

It all seems to be there in perfectly obvious black and white.