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Comment by burntcookie90 | Hacker News Reader

Think of it a a $2500 5k monitor shipping with a computer for free

Unfortunately you can't hook up a powerful workstation to that monitor :/

If this holds true you should be able to: http://support.apple.com/kb/ht3924#12

I don't think that will work here - TB2 is derived from DP1.2, which only goes up to 4K@60hz. You'll have to wait for TB3 to drive an external 5K monitor from a Mac.

Like I have posted elsewhere already: 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.

Doesn't TB2 have two interleaved streams, one carrying DP1.2 and the other carrying 20Gbps PCI-E? Even if the PCI-E stream has enough bandwidth for 5K in theory, the ecosystem isn't in place to use it as a display output. That's what the DP part is for.

You're ignoring signalling and overhead. The actual usable bandwidth is about 17.3Gbps, thus not enough (for 60fps uncompressed stream).

DisplayPort v1.3 can deliver 25.92Gbps of usable bandwidth, thus required for 5k [1].

[1] http://www.extremetech.com/electronics/190130-displayport-1-...

You should divide 20Gbps by 9 bits (2275 MB/s) or even by 10 (2048 MB/s), not by 8, because in addition to useful payload, there are also packet headers and control packets being transferred. So it actually doesn't.

"Packet headers and control packets" are not the reason you should divide by 10. The reason is that Thunderbolt uses 8b-10b encoding so 1 byte of data is transferred as 10 physical bits. Therefore the maximum theoretical usable bandwidth is 20e9/10/1024/1024 = 1907 MiB/sec. Then on top of that you have to deduct the overhead from packet headers and control packets so the real-world usable bandwidth is even less than 1970 MiB/sec...

I believe 2560 is the post-coding bandwidth. Links are usually 3.125 Gbps before coding.

For other people to play with this, just google "(5120 * 2880 * 3 * 60) bytes/s in Gib/s" to get the answer (just short of TB2s 20GiB/s assuming no overheads.

At some point you could use the iMac as a screen can it still me done ?

I would imagine as long as the video card has similar specs as the new iMac, and the computer had Thunderbolt 2, then yes (at 5k). Otherwise, it would be scaled somehow or just not work at all.

Computer for free? With Mac everything costs money, there is hardly no way to enjoy this piece of hardware without spending money to the Mac way of money sucking.. I enjoy my arch linux system every single day, and it never cost me a cent, there is no backdoors, money sucking thing going on at all. But, for those who believe the marketing slogan that everything with Mac is better, well, grab your wallet and join the idiots.

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