4 ms·

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

alexgaribay 12y ago
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.
- gambiting 12y ago
  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.
  - Shebanator 12y ago
    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.
    - nullz 12y ago
      The above calculation was for 32bpp: 3 colors * 1 byte * (8 bits/byte) = 32 bits
      - gambiting 12y ago
        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.
        Shebanator 12y ago
        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 http://en.wikipedia.org/wiki/DisplayPort#Specifications
  - brigade 12y ago
    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
MHordecki 12y ago
Even if the GPU does, DisplayPort 1.2 doesn't support 5K displays.

alexgaribay 12y ago

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.

gambiting 12y ago
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.
- Shebanator 12y ago
  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.
  - nullz 12y ago
    The above calculation was for 32bpp: 3 colors * 1 byte * (8 bits/byte) = 32 bits
    - gambiting 12y ago
      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.
      - Shebanator 12y ago
        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 http://en.wikipedia.org/wiki/DisplayPort#Specifications
- brigade 12y ago
  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

MHordecki 12y ago

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