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mattnfg1

macrumors newbie
Original poster
Dec 29, 2019
7
2
Hi All.

I am considering a Mac Pro purchase and have some questions around the spec and specifically the graphics options.

First of all, my use case is going to be mainly working with 4k video in Final Cut Pro - I do a little bit of audio work, but mainly video. I would like to drive 2 Pro Display XDR's also.

In this case, would you go for 2 x Radeon Pro W5700X's or just 1 x Pro Vega II (my budget won't stretch much further than that).

Although the Vega II seems to be priced as the better card, I would be interested if anyone could enlighten me as to why the W5700X can drive 3 Pro Display XDR's where as the Vega II can only drive two (making it sound less powerful, but im sure it's not as simple as that).

Also, I wonder if the system would work better with 2 x 5700X's driving one Pro Display each, rather than having two of them running off a single Vega II?

Finally, I would be keen to understand the difference between GDDR6 and HBM2 memory on the 2 cards.

Many thanks
 

joevt

macrumors 604
Jun 21, 2012
6,968
4,262
Vega II has better compute but it's older so it doesn't support Display Stream Compression (DSC). Without DSC, it takes two DisplayPort HBR3 signals to drive the 6K display. An AMD card has 6 DisplayPort outputs, so the Vega II can drive three XDR displays though Apple says only two is supported. 6K using two HBR3 signals is 36.6 Gbps which reduces USB performance of the USB hub of the XDR (because Thunderbolt 3 only has 40 Gbps).

Navi cards like the W5700X support DSC which effectively triples the bandwidth so it can drive a 6K display with a single DisplayPort HBR2 connection which leaves much more room for USB 3.0 from the USB hub of the XDR. Maybe Apple says it supports 3 but it might support 4 (no one has tried - there's enough DisplayPort outputs for 6 XDR displays but there may be a limitation based on pixels or DSC capability).
 
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