GT120 Slow Performance and FCPX

In my attempt to build a system that can run DaVinci Resolve and FCPX, I just tried a change that led to mixed results.

Machine: MacPro 2,1
RAM: 24
Storage: 6tb CalDigit Raid 0 (Slot 4 8X)
Graphics: Nvidia GT120 for GUI (Slot 2 1X)
Graphics 2: GTX285 for GPU (Slot 1 16X)
Video: Black Magic StudioLink SDI (Slot 3 1X)


Before the DaVinci experiment, I had a Radeon 4870 as my only graphics card. FCP X played flawlessly at speed. So did FCP 7 and Premiere

After swapping out the Radeon for the 2 Nvidia cards, here's what happened:

1) FCPX is really choppy and now playing back at about 8 - 10 FPS on both my main screen and my external AV monitor.

2) FCP7 plays fine on the main screen and through the AV Monitor

3) Premiere plays choppy on the main screen but fine through the AV Monitor.

4) Resolve plays choppy on both the GUI screen and AV Monitor

So here's what I want to know: Is the crappy FCP X performance from the GT120 related to:

1) being a crappy card?,
2) being in a 1X slot (it's hard to put it in a faster slot because of the CalDigit card)?
3) being in a 2,1 MacPro?

Has anyone had acceptable FCPX performance from a GT120 on any MacPro (of the same or higher spec)?

Any thoughts?

FCP X doesn't play well with multiple GPUs.
What was the reason for 2 GPU cards?

The reason for the 2nd GPU is because DaVinci Resolve wants 2 GPUs: one for the GUI and one for rendering. The combination of the GT120 for GUI and GTX285 for render is one of DaVinci's favored combinations.

I tried plugging the monitors into the 285 and it works much better for FCPX but not for DaVinci. I'm not sure having the 2nd GPU is what's causing the problem, but it's worth investigating. It's a non-starter, at any rate, because I need both cards for DaVinci to work.

The point of having them both at once is so that I can work in FCPX and send to DaVinci for color correction and round trip back to FCPX for mastering/output.

And thus one of my issues with the "hype" about using Resolve and FCP X on the same system. They each want different GPU specs (multiple vs single, OpenCL vs CUDA). But if you can get it to work, great! It is a nice workflow.

I guess my shout out is to investigate the general performance of the GT120 for FCPX. Even though Apple specs it as acceptable for FCPX, are folks having any speed issues with it?

One of my problems is that I'm using it in a 2,1 Mac Pro, which is not up to spec for the use of the card. It functions, can drive my 30inch and 24inch monitors, but it is dog-slow and can't be used for editing (at least the way I have it now.)

What I'm curious about is whether it works better in more lanes (4X or 8X) or would be the same problem because it's either too slow in general or not well suited to my machine.

Good question! I don't know that specifically. But I do know if you plug 2 monitors into one GPU you cut it's RAM allocation in half, so FCP X, Motion, etc, can only access half the RAM on the card. Could that have something to do with it?

It does! I just re-allocated my lanes using the Expansion Utility in Core Services, so that each graphics card is getting 8X and the RAID and Black Magic card are getting 1X. Now playback from FCPX is smooth with no dropped frames.

Resolve seems to be OK with having the 285 on a 8x slot as opposed to 16x, so i'll see if it makes a difference for rendering, playback or both...



Thanks BenB....