27" iMac GPU options

dimme

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I am looking at getting a 2019 iMac 27" to replace my 27" 2015. Besides the normal web surfing and office stuff I use Lightroom and Photoshop. Once in a while I may game with X-Plane. I think the Radeon Pro 580X should be good for me. Or do I need to be taken into the Vega 48? Where do you see the difference in the 2 cards?
Thanks
 
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quagmire

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I would bump up to the Vega. The 580X performs worse than the 1060. No data on the Vega 48 yet, but I imagine it will be between a 1060-1070( Vega 56 included to give a rough estimate). When it comes to Apple, always get the best GPU you can afford. May not use its full power now, but down the road you may need it.

https://www.videocardbenchmark.net/compare/Radeon-RX-580X-vs-Radeon-Pro-Vega-56-vs-GeForce-GTX-1060/4055vs3912vs3548

https://www.videocardbenchmark.net/compare/Radeon-RX-580X-vs-GeForce-GTX-1060-vs-GeForce-GTX-1070/4055vs3548vs3521
 

macduke

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Remember if you're primarily gaming on the Mac, you could always add an eGPU down the road which adds that performance on top of your existing GPU. Maybe someday Windows will support eGPUs in bootcamp as well (unless someone has already figured it out, which I wouldn't doubt since I don't keep super on top of that stuff).

I would bump up to the Vega. The 580X performs worse than the 1060. No data on the Vega 48 yet, but I imagine it will be between a 1060-1070( Vega 56 included to give a rough estimate). When it comes to Apple, always get the best GPU you can afford. May not use its full power now, but down the road you may need it.

https://www.videocardbenchmark.net/compare/Radeon-RX-580X-vs-Radeon-Pro-Vega-56-vs-GeForce-GTX-1060/4055vs3912vs3548

https://www.videocardbenchmark.net/compare/Radeon-RX-580X-vs-GeForce-GTX-1060-vs-GeForce-GTX-1070/4055vs3548vs3521
I'd estimate that it's the same percentage slower than the 56 as the 56 is slower than the 64, based on the fact that the numbers relate directly to the enabled compute cores, though it may be dialed back a bit for thermals over a sustained period. Depends on whether AMD is making this new chip on their 7nm process (cooler), which would be fairly surprisingly but not entirely unlikely. So maybe 15% slower than Vega 56, which I think should put it within range of a standard GTX 1080 based on floating point, maybe a little slower? Not bad, especially if you bootcamp and run 1440p since I believe the display is already locked to 60Hz.
 

quagmire

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Remember if you're primarily gaming on the Mac, you could always add an eGPU down the road which adds that performance on top of your existing GPU. Maybe someday Windows will support eGPUs in bootcamp as well (unless someone has already figured it out, which I wouldn't doubt since I don't keep super on top of that stuff).


I'd estimate that it's the same percentage slower than the 56 as the 56 is slower than the 64, based on the fact that the numbers relate directly to the enabled compute cores, though it may be dialed back a bit for thermals over a sustained period. Depends on whether AMD is making this new chip on their 7nm process (cooler), which would be fairly surprisingly but not entirely unlikely. So maybe 15% slower than Vega 56, which I think should put it within range of a standard GTX 1080 based on floating point, maybe a little slower? Not bad, especially if you bootcamp and run 1440p since I believe the display is already locked to 60Hz.
Can't imagine the 48 being close to the 1080 considering both the 56 and 64 lag behind the 1080.

https://www.videocardbenchmark.net/compare/Radeon-RX-Vega-56-vs-Radeon-RX-Vega-64-vs-GeForce-GTX-1080/3821vs3808vs3502
 

macduke

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Can't imagine the 48 being close to the 1080 considering both the 56 and 64 lag behind the 1080.

https://www.videocardbenchmark.net/compare/Radeon-RX-Vega-56-vs-Radeon-RX-Vega-64-vs-GeForce-GTX-1080/3821vs3808vs3502
Well, I was talking about floating point, which the 56 is 10.5Tflops and the RTX 1080 is 9Tflops. But yeah, that's not the whole story. Apple's GPUs always seem to lag behind in gaming, but especially in the case of Vega, it's optimized for more specialized computing tasks and less for gaming.
 

fokmik

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I'm shying away form the Vega because of the heat it may generate.
Dont!! Vega 20 is performing far better than the 560x into the mbp 2018 from heat stand point and performance so here is the same thing vega will be not as hot as the 580x
 

Pressure

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If the Apple invented name follows the logic of the VEGA 56 and VEGA 64, then the VEGA 48 should have 3.072 shaders.

This may be a great way to salvage VEGA10 dies for AMD. Apple clearly asked for a better option than Polaris.

Undervolted VEGA10 is quite nice.
 

dimme

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$450 is a lot for a built in GPU and is over my budget.. Will Photoshop and Lightroom use it?
 
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smirking

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Remember if you're primarily gaming on the Mac, you could always add an eGPU down the road which adds that performance on top of your existing GPU.
I don't think you should rely on that. An eGPU is a great option for addressing an underpowered GPU, but I wouldn't count on it being ideal, especially when 5K displays are involved. The implementation of the BlackMagic eGPUs have been spotty to date and none of the other eGPUs can drive a 5K display.

Even when eGPUs work well, you're still not getting the full benefit that you'd get if they were a native card.
 
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macduke

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I don't think you should rely on that. An eGPU is a great option for addressing an underpowered GPU, but I wouldn't count on it being ideal, especially when 5K displays are involved. The implementation of the BlackMagic eGPUs have been spotty to date and none of the other eGPUs can drive a 5K display.

Even when eGPUs work well, you're still not getting the full benefit that you'd get if they were a native card.
Do many iMac gamers run 5K games? I'd think they were doing 1440p. That's what I plan on doing in bootcamp and I bought the Vega 48.
 

smirking

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Do many iMac gamers run 5K games? I'd think they were doing 1440p. That's what I plan on doing in bootcamp and I bought the Vega 48.
I don't know, but the OP's question was in reference to an iMac. I assume he's going to be using a 5K monitor. That 5K monitor is awesome, but is also a curse if you're needing to find a way to supplement the horsepower of your rig. I have an LG 5K. I love it, but it really limits my options and my limited forrays into using an eGPU have been disappointing.
 

macduke

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I don't know, but the OP's question was in reference to an iMac. I assume he's going to be using a 5K monitor. That 5K monitor is awesome, but is also a curse if you're needing to find a way to supplement the horsepower of your rig. I have an LG 5K. I love it, but it really limits my options and my limited forrays into using an eGPU have been disappointing.
Well you can use the 5K display but you only run the resolution at 1440p in the game. Not ideal but it will probably be years before Apple gives us a GPU that can run the 5K display natively in games with decent settings at 60fps. At least in an iMac. I bet the new Mac Pro will be able to.
 

CWallace

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I would expect the Vega 48 to be better than the RX580. That being said, I expect the main difference to be in video production applications. For games (especially Windows under BootCamp), I imagine it won't be that much better.

One can expect https://barefeats.com will be running tests once they get their hands on the hardware.
 

Jimmdean

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Anyone know the performance difference between the 2017 580 and the new 580X? What does the X give you exactly?
They appear to be clock increases of the previous parts that AMD hasn't even announced yet. When they did that with the 560x (vs 560) it was pretty negligible. Granted it could be a marketing thing and they used better chips, but kept the naming convention in line with the Macbook Pro, but I doubt it.
 
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smirking

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Well you can use the 5K display but you only run the resolution at 1440p in the game.
I don't think downsampling the resolution is going to make a difference in this case. No GPU other than the BlackMagics can power a 5K at any resolution unless there have been some new developments I missed in the past couple of months. It's not an issue of rendering power. It's an issue of being able to fully utilize TB3 bandwidth to drive a display.
 

Donka

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All the news sites are reporting a 50% increase in gpu performance...

‘Radeon Pro Vega 20 graphics can be added to the 21.5-inch iMac, delivering up to 80 percent faster graphics performance than the previous model. The 27-inch iMac with optional Radeon Pro Vega 48 now delivers up to 50 percent faster graphics performance.’
 

macduke

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I don't think downsampling the resolution is going to make a difference in this case. No GPU other than the BlackMagics can power a 5K at any resolution unless there have been some new developments I missed in the past couple of months. It's not an issue of rendering power. It's an issue of being able to fully utilize TB3 bandwidth to drive a display.
I’m talking about the internal 5K display at 1440p.
 

loybond

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AFAIK, yes, they'll use it, but for limited effects. Photoshop uses the GPU for example when you rotate an image. Lightroom uses it when you're using brushes. Any discrete GPU does the job. Final Cut and video apps use the GPU more, but don't max out the GPU either.

$450 is a lot for a built in GPU and is over my budget.. Will Photoshop and Lightroom use it?
 
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smirking

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I thought I saw someone do this with a MBP but maybe I’m wrong?
Plenty of people are doing it with MBPs, but those aren't 5K screens. I just wasn't sure about iMacs with 5K screens, but I found the following Apple Knowledgebase article that suggests that you're right that an eGPU can be paired successfully with a 5K iMac running Mojave.
https://support.apple.com/en-us/HT208544

It mentions that you can set Mojave to prefer the eGPU and it specifically calls out that it includes the built-in display of an iMac, iMac Pro, and Macbook Air. So I'll take that to mean a yes, but I'd like to see some numbers on what kind of performance penalty you have with an eGPU vs a dGPU.
 
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Zarniwoop

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What Vega 48 can offer for 5K iMac is the memory bandwidth. Even if the GPU does not provide that much raw horse power, it’ll give the pixel hungry 5k display a long needed bandwith for pixel push. Also 8Gb GDDR5 creates a lot of extra heat that HBM does not, so Apple could in theory give the thermals for the GPU.
 
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dimme

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Also 8Gb GDDR5 creates a lot of extra heat that HBM does not, so Apple could in theory give the thermals for the GPU.
Please explain I am not familiar with HBM? Are you saying the Vega will produce less heat that the stock card?