That has been one of the problems with the Mac, compared to generic PCs. The cost of graphics cards and the trend to only have integrated graphic chipsets (whether Intel, AMD or nVidia), which has hampered GPGPU processing on the Mac. On the PC side, where high performance graphics cards are more reasonably priced and most systems have PCI-E slots, the use of GPGPU to accelerate mathematical tasks, such as Photoshop filters, video editing, prime searches etc. (they offer up to around 10x performance over doing the calculations with the CPU) has really taken off over the last few years.

If you are really going for heavy processing, then the nVidia Tesla add-ons are fairly amazing.

I'd dearly love them to do a 27" iMac with a serious graphics card (say an R9 Fury or a GTX 980) but I suspect there's no way to fit one of those with the necessary cooling into the iMac form factor. As it stands the only even vaguely powerful graphics chipset on Mac requires you to spend either £2K on a Macbook Pro or £2.5K on a Mac Pro...

That was one of the things that attracted me to the 24" iMac, that it had a graphics slot and you could upgrade the graphics card... Then six months later they brought out a new model and abandoned it, since then they have tried to make the iMac as thin as possible and thus reduce its ability to use high end components, due to the lack of cooling. Yes, the iMac is now very thin, especially at the edges, but I sit in front of the screen, so if it is 2cm of 7cm thick doesn't make a jot of difference to me, but it does restrict me to cooler running notebook parts, as opposed to high performance chips.

All this talk of graphics cards comes at an opportune moment since I've just discovered that neither of the cards out of the 2,1 Mac Pro work in my new 3,1 Mac.

Since I need 2 cards in order to run all 3 displays, I am looking for a second one. Is there any point getting a better graphics card than the one already fitted - an ATI Radeon HD 2600 XT - given that at least one of the displays will be driven by it, in which case would it be best just to get a second the same? (In my old 2,1 Mac Pro I had the two main displays run off the best card - NVIDIA Quadro FX 4500 - and my palettes display of the other one - NVIDIA GeForce 7300 GT - and TBH I didn't notice any slowdown of the overall graphics speed when I added the second less powerful card.)

Also according to the specs on Everymac.com two of the PCI slots are x16 and the other two are x4. I'm assuming that the double-height slot (#1) which has the graphics card fitted is one of the x16, however which is the other - the next one up (#2)?

Slots 1 and 2 (the one with the graphics card and the one above it) are the 16x PCIe gen 2 slots. Slots 3 and 4 are PCIe gen 1 4x slots so you will want to use the slot directly above the exisitng graphics card for optimum performance.

I had a Radeon 5770 upgrade kit in my Mac Pro 3.1 and I'm not totally convinced there was a massive amount of difference to what I was doing tbh - plus it's not an officially supported upgrade (although it worked just fine but you needed to be using a sufficiently recent version of OS X (10.6.3 as a minimum IIRC) to get the drivers - the original install discs weren't new enough). Then again, I probably wasn't doing anything sufficiently taxing to expose much of a difference between the XT2600 and the 5770 anyway. The 5770 can drive 3 displays (one via DVI and two via the miniDP connectors) IIRC although I seem to recall some people had issues with it working consistently (I only had one display and experienced no issues).
Also worth noting is that the 5770 required at least one additional power connector (there are two on the motherboard) so you need to consider how many power connectors a more powerful card requires. From memory the 5770 needed one and the 5870 needed 2.

Thanks! That's what I was hoping regarding the slots. Both power connectors on the motherboard are currently free and I don't have anything else that requires them, so I'll have a look at my various options for a second card.

I've never really noticed any difference in performance between the various displays on my last system despite the fact that one of them was being driven by what should have been a significantly less powerful card. Also I did an upgrade of a 2010 MacPro last month for a client that included swapping out the Quadro K4000 card for a K5000. For it's main use which is 3D modelling the K5000 was noticeably faster on the live preview but in the Adobe apps we couldn't see any real improvement.

Despite what big_D says about the latest graphics cards I've not been disappointed by the performance of my old system, nearly all Photoshop filters rendered in seconds at worst for all but the most enormous files. In fact the biggest performance bottleneck was opening and saving any Illustrator file that contained large placed Photoshop files. I once artworked a graphics wrap for a whole tram (5 carriages both sides) that was done as a single piece for each side and each open or save action in Illustrator took about 5 minutes once the Photoshop background had been placed.

The graphics card performance is only really noticeable if you are driving high resolutions and 3D rendering. If you aren't using 3D, then pretty much any card will be fast enough.

On the Windows side, using large graphics files (several hundred MB), using the GPGPU to do the transforms in Adobe CC means that you can preview the changes on the complete image in near real time (depending on filter and graphics card), whereas a preview "thumbnail" in the dialog would take several seconds to render with just the CPU.


https://helpx.adobe.com/photoshop/kb/ph ... d-faq.html

Does OpenGL and OpenCL overhaul your editing experience?
Edit: The Benchmarks page for CS6 are interesting. The article is of course a bit dated, but you get an idea of the performance benefits that OpenCL will give you.

Thanks big_D. From reading the information in those two links it appears that most of the benefit is aimed at 3D and Photoshop users. Since I spend nearly all my time in InDesign then it looks as though GPU performance isn't going to be a serious issue for me. The only interesting thing I did read in the first link was that Adobe recommend using identical makes and models when using multiple graphics cards (although I didn't have any problems with my last Mac which had two different cards - but both from NVIDIA). Since the current graphics card in this new Mac Pro is performing perfectly adequately for my needs I'll look for another the same.

That should only be important for GPGPU enabled filters in Photoshop - and it is only a recommendation, because it can cause driver clashes; again that might be something more aimed at Windows users.

That's good to hear, as a duplicate for the card I already have that's been flashed to work in a Mac is proving to be illusive and costly.

Looking at that list of filters again, the only one I use with any frequency is "Smart Sharpen".