Two NVidia GPUs for extra displays?

[TheBloke]

Hi all

 

I am currently using an NVidia 760 with four connected displays.  (I also own a 980Ti but it lags terribly so I reverted to the Kepler 760 which runs much better.)

 

I would like to add at least one more display.  I first tried to achieve this with a supposedly macOS-compatible USB 3 to DVI adapter, but this is not working at all for me.  I thought I had to go this route because I am using every PCIe slot on my mobo except for one PCIe x1 slot.

 

I've now realised, rather late, that actually there is a modern NVidia GPU available on a PCIe x1 card, the Zotac GeForce GT 710.  (And it's actually cheaper than I just spent trying to get USB 3 to DVI!)

 

It uses the NVidia 208 GPU, which is Kepler and so should work OK with either the Native or Web drivers.

 

So my question: will macOS detect and use two separate NVidia GPUs, and allow me to simultaneously use displays connected to both?

 

It should work fine in Windows (at least as long as I'm pairing it with another 700 series GPU), but I have no idea if this is a supported config in a Mac.  If anyone knows for sure I'd be most grateful for info.

 

Thanks.

[maleorderbride]

Yes, you can use multiple nvidia GPUs. Obviously the VGA connector won't work on that GT 710, but the DVI and HDMI should.

[TheBloke]

Yes, you can use multiple nvidia GPUs. Obviously the VGA connector won't work on that GT 710, but the DVI and HDMI should.

 

Thanks a lot, that's great to hear.

 

PS. Why is it obvious the VGA won't work?  Analogue output is no longer supported in macOS?   I had no plan to use the VGA, just curious!

[TheBloke]

One more question:  do you know if it would work to have two different types of GPU, eg one NVidia and one AMD?   Would macOS load both drivers and let them both work in parallel?

 

That's kind of like what happened when I used the USB 3->DVI adapter: I had four screens on the NVidia, and one screen on the USB adapter, and that was supported (it didn't actually display a usable picture, but that's because the USB adapter drivers are shot.)   So maybe if it works there it would work with any two GPUs?

 

I'm just wondering whether, if I'm going to get a second GPU, I should make it an AMD one given they seem to work better.  I don't think there's an AMD on a x1 slot (EDIT: There's a FirePro, but it's expensive and only has one output.)  But I do have the option of replacing my 2 x 10GB adapters with a dual-port to free up a x8 slot.

[maleorderbride]

Analog isn't supported any more (since 10.12). One can get it via adapter if necessary.

 

I've had a mixed GPU system like that in 10.8 or 10.9 and it worked. I can't speak to anything newer, but it should be OK. 

 

Also, I just googled the GT 710 and read some conflicting reports about MacOS support. It should be a supported model by the native drivers in 10.13 though.

[TheBloke]

Great, thanks a lot for the confirmation.

 

Yeah I've read a few posts on the 710. It definitely works as of Sierra.  There's a couple of posts on 'the other forum' indicating some issues as of High Sierra.  But with no followup to them, you never know what might be the cause.  Anyway I'm more than happy to use Native drivers, in fact I'm booted with them right now.  I can't tell any difference between Native and Web when using a Kepler card.

 

However I do still have one technical problem:  the card is a PCIe 3.0 x1 card.  I have only PCIe 2.0.  Normally I'd expect the card to work fine, just at a lower bandwidth.   However some small details give me some doubt - for example, on the Amazon listing, it has two alternate cards:  "PCIe 3.0 x1" and "PCIe 2.0", the latter being a standard x16 card.  Maybe implying that if you want PCIe 2.0 you need the other card.

 

Although PCIe 2.0 x1 is not much bandwidth, I hope it should be OK for what I want - no 3D, just one or two extra 2D screens.  But I'm worried they may have made PCIe 3.0 a requirement, and the card may simply refuse to work.   I've emailed Zotac and also added a question on Amazon, but no replies as yet.  Of course I can always just return it on Amazon if it doesn't work, so assuming I don't get a definite "no" I'm likely to buy it anyway to find out myself.

 

I did wonder whether, even if the card works, the bandwidth would limit my ability to use more than one monitor.  I looked up the bandwidth requirements of monitor cables, and for example 1080p at 60fps use about 4Gb/s, which is almost exactly the same as the bandwidth one PCIe 2.0 x1 slot can provide.  However, I am assuming this is not the actual limit because the GPU generates the picture itself, and I assume the bandwidth between CPU and GPU is much less than this.  Maybe in 3D the CPU has to send high-bandwidth instructions, but in 2D it would presumably only send occasional frames, or part frames, as something changes, and the GPU caches that and re-displays it the required 60 times a second.  Even videos are nowadays decoded on the GPU.

 

So I am hoping the available bandwidth of PCIe 2.0 x1 is definitely fine for one, and hopefully two extra screens, as long as I'm not doing much 3D.  And assuming the card doesn't require PCIe 3.0 to function at all.

 

All that said, I may still do what I mentioned earlier - replace 2x10GB with 1xdual, such that I could then fit a 16x card running at 8x speed.  

 

I'll see what AMD cards are available and affordable on the used market, as it might be interesting to get an AMD and use it as my primary card for 3 or 4x monitors, with the balance on the 760.  To see if that gives me a smoother desktop experience, as AMD macOS drivers are hopefully better than the  NVidia equivalents. 

 

Things are generally OK with my 760 on either Native or Web, but I do still see occasional blips of lag, especially when I have a full screen video playing (eg YouTube). I never saw this in Windows 10 and it would be nice to eradicate it.

[TheBloke]

Or of course I could sell the 760 (for £80-£100 it seems) and buy an equivalent AMD card, plus a secondary lesser AMD as discussed, and maybe get a smoother overall experience by being 100% AMD

 

Too many possible permutations!

 

EDIT:  Hmm, there's an Asus Radeon HD 7970 with 6 x DisplayPort outputs!  And if I sold my 760 it would work out less extra than I planned to spend on a second GPU.  But I don't know if all six displays can actually be used - it talks about Eyefinity 6 which I know is screen-stretching tech.  So maybe it can't support five or six independent screens as I would want.    Especially as one of them is 4K.

 

Anyway I know this is a bit OT for this thread now, I'll do more research and raise it up in the AMD forum if necessary.

[Cyberdevs]

Or of course I could sell the 760 (for £80-£100 it seems) and buy an equivalent AMD card, plus a secondary lesser AMD as discussed, and maybe get a smoother overall experience by being 100% AMD

 

Too many possible permutations!

 

EDIT:  Hmm, there's an Asus Radeon HD 7970 with 6 x DisplayPort outputs!  And if I sold my 760 it would work out less extra than I planned to spend on a second GPU.  But I don't know if all six displays can actually be used - it talks about Eyefinity 6 which I know is screen-stretching tech.  So maybe it can't support five or six independent screens as I would want.    Especially as one of them is 4K.

 

Anyway I know this is a bit OT for this thread now, I'll do more research and raise it up in the AMD forum if necessary.

Today I swapped my 1070 with my older AMD 7790 and it the results are unbelievable, it feels like I upgraded my computer from a 8086 pc with a SkyLake ( I actually have a Skylake processor )

 

If you use radeonDeInit I believe you'll have all the ports active on your 7970 (If you decide to change your GPU). You can also ask the guys to help you create a custom SSDT for any AMD GPUs so you can have all the ports active on them.

 

I also ordered a Sapphire RX 580 Nitro+ Special Edition so I'll be putting my 1070 back in its pack for now until we find a proper solution for the miserable performance on the nVidia GPUs.

 

I would defiantly go for Vega but the price is too high right now, no thanks to miners!!

[Peke]

Or of course I could sell the 760 (for £80-£100 it seems) and buy an equivalent AMD card, plus a secondary lesser AMD as discussed, and maybe get a smoother overall experience by being 100% AMD

 

Too many possible permutations!

 

EDIT:  Hmm, there's an Asus Radeon HD 7970 with 6 x DisplayPort outputs!  And if I sold my 760 it would work out less extra than I planned to spend on a second GPU.  But I don't know if all six displays can actually be used - it talks about Eyefinity 6 which I know is screen-stretching tech.  So maybe it can't support five or six independent screens as I would want.    Especially as one of them is 4K.

 

Anyway I know this is a bit OT for this thread now, I'll do more research and raise it up in the AMD forum if necessary.

 

I own a 980ti 6gb  and Im not experiencing lag if anything in general. Of course is not as smooth as windows for sure (because crappy Nvidia web drivers) but it works ok even in FCPX 10.4 without issues.

 

im using .104. and work ok with DVI and HDMI as far I tested before.

[TheBloke]

Today I swapped my 1070 with my older AMD 7790 and it the results are unbelievable, it feels like I upgraded my computer from a 8086 pc with a SkyLake ( I actually have a Skylake processor )

 

If you use radeonDeInit I believe you'll have all the ports active on your 7970 (If you decide to change your GPU). You can also ask the guys to help you create a custom SSDT for any AMD GPUs so you can have all the ports active on them.

 

I also ordered a Sapphire RX 580 Nitro+ Special Edition so I'll be putting my 1070 back in its pack for now until we find a proper solution for the miserable performance on the nVidia GPUs.

 

I would defiantly go for Vega but the price is too high right now, no thanks to miners!!

 

Wow OK, thanks!  I definitely want one now.  One card with six outputs would be the perfect solution - I could just swap out my 760 for that, I wouldn't have to make any changes to other PCIe slots, it'd be perfect.   

 

Really pleased to hear you're getting smooth performance now.  From reading your experiences in the other thread, things weren't nearly as bad for me as they were for you.  But my 760 still isn't completely smooth.  Things like Mission Control and swipe left/right a space always cause a full screen video to pause a few frames.  And Mission Control's animation sometimes seems to take a moment before it activates, as does swiping spaces - and sometimes I can tell there's a little judder in there.

 

It's not work-breaking, but it'd be nice to have it gone.  And if I can do that in conjuction with adding another monitor, that'd be amazing.

 

Thanks so much, I will definitely research that deInit/SSDT thing and confirm in the AMD forum that I could use all six outputs.  Or just five would be enough - I don't think I have room on my desk for a sixth monitor   Though it would actually be six displays in total, as I have my iPad mounted on top of my keyboard and connected using Duet, providing a handy place to display my email client.  That also gives me a virtual Touch Bar which is nice to have.

 

And actually I see that there are quite a few AMD cards with five outputs.  So if I definitely won't use the sixth, I have a lot more cards to choose from that have five.  Some use mini-DP ports, but I have at least one or two adapters gathering dust in a drawer from the days when I had a real MacBook

 

 

I own a 980ti 6gb  and Im not experiencing lag if anything in general. Of course is not as smooth as windows for sure (because crappy Nvidia web drivers) but it works ok even in FCPX 10.4 without issues.

 

im using .104. and work ok with DVI and HDMI as far I tested before.

 

That's interesting - for me the 980Ti was pretty bad using both 106 and 158 drivers.  Noticeably sluggish, playing videos juddering for 1-2 seconds after any major activity on other screens (eg swipe Space left), and just generally feeling slow and unresponsive.    My 760 was night and day better, with either Native or Web drivers.

 

So I figured it was a difference between Kepler and Maxwell cards - Kepler works OK, Maxwell not.  But if it works fine for you, clearly that's not all there is to it.  It must depend on other factors too.

 

How many displays do you have connected?  I have with four monitors, one of which is at 4K.  Maybe if you have a smaller combined desktop resolution that could be making a difference?

 

Anyway I'm glad it's working well for you.  I'm not playing any games at the moment but I will want to in future, so it's annoying that I'll have to swap back in the 980Ti whenever I want to do so, then out again to go back to macOS.

[Peke]

I got two monitors setup normally. Now only one connected but on Monday (I go out of the city) I will do some testing with both at different resolutions to check.

 

You can test with only 2 of yours at lower resolutions with the 980ti and see if your problems persists.