Mac Pro classic GPU questions!

[Powermange]

Hello everyone. Like many others I've recently brought an older Mac Pro 4,1 up to speed with SSD, more memory and PC BIOS Graphics card. Thanks to where thanks is due. (Netkas, Rominator, AppleEFI, Cindori etc.) for writing so many great guides for all of us.

I now use a XFX Radeon 6870 to drive three screen (27" LED mDP, 20" ACD DVI & 23" ACD DVI), great. But since no EFI on that card no boot screen. Not a huge problem as I don't use boot camp often and can use boot champ etc. But I still want to be able to to recoveries etc in EFI if necessary so I've kept the GT120 in slot4 just in case.

Can this be a bad thing? Like software accidentally using much slower GT120 instead of better 6870? (Not the best available I know but very cost effective and lots of connectors, Heaven went from single digits fps to reasonably smooth).

Does the monitor connected to card affect performance?

Is all acceleration based on the screen connected to certain card or irrespective of? Does it depend on the software? What if I edit images on center screen (fast card) and keep toolbars on side screen (old card), what card would accelerate?

Im thinking I could leave one screen on the gt120 for boot screen if that doesn't come with problems.

Another option would be to EFI flash the card but from what I've read I would loose the upper DVI doing so?! Maybe i should just try the flash and se what happens.

Ive read many threads but not been able to get my head around this, please shed some light!

 

[gpzjock]

If you are worried about the GT120 interfering, remove it and only put it in slot 4 when you need a boot screen.
I have a 8800GT for exactly that purpose, it sits in the padded case it came in. My flashed Sapphire Vapor-X 5870 runs a 24" monitor and 42" LCD TV just fine without it.

 

[m4v3r1ck]

Why not use the input selector on one of your monitors, to (de)select the GT120 (1) or Radeon (2) for boot-screen maintenance?

Gl & Cheers

 

[ActionableMango]

It has been a long time since I've read about 6870s. IIRC, after flashing you (A) only get boot screens on the lower DVI port, and (B) lose the ability to use the upper DVI port.

If you want full PCIe 2.0 speed, you have to do the resistor mod.
https://forums.macrumors.com/threads/1547340/

I have not done any of this myself. I decided to go with a GTX680 since they are so easy to flash and really have no drawbacks whatsoever.

 

[Powermange]

Thanks for all responses.

@gpzjock, yep i think ill do just that thanks.

@bdm, not sure what you mean "input selector" dont think my screens have that, unless youre being funny and mean the dvi cable :-/

@actionablemange, yes thats what ive been able to gather. Dont really understand it though, if the efi bios is the normal bios with efi added why would a dvi port disappear? Oh well. The upper i believe is the dual link one im hoping tO get a 30" acd soon so. Not a good option, until a upgrade to 680 or otherwise im gonna go with @gpzjock's method and put the gt120 in if and when needed. And the resistor mod, never seen that thread WOW the length one can go to hack a card, impressive but not in my plans for the near future. Thanks for the tip though.

Im still wondering though if someone can explain whether there are downsides or not to just leaving it in there unplugged! Powerdrain? Obstruction of ventilation? Collisions betwen gpu's?

 

[m4v3r1ck]

@bdm, not sure what you mean "input selector" dont think my screens have that, unless youre being funny and mean the dvi cable :-/

No, never making fun about serious issues....

I meant why not hook one monitor to both gpu's, so you can select your GT120 with your monitor's input-selector, when bootscreen / maintenance is needed?

GL & Cheers

 

[Powermange]

Ok now i get it. Yes that would be clean and practical. Theese apple displays only have one input so would require a little switchbox, but still good idea. I will pull the card though for now. See how often i will need the boot screen. Tha ks

 

[ActionableMango]

Dont really understand it though, if the efi bios is the normal bios with efi added why would a dvi port disappear? Oh well. The upper i believe is the dual link one im hoping tO get a 30" acd soon so.

IIRC, the history behind this is that there was never a 6870 in a MAC. The EFI portion of the 6870 ROM you have was reverse engineered from a similar, but not identical GPU in an iMac or something.

According to the following diagram, the upper port is actually the single link port, so you should be good to go.

 

[Powermange]

At first i didnt believe that schematic but yes its correct (of course) i just didnt understand dvi enough, now I think I do.

Since last post I've bought, sold and traded monitors so I now have 1 30" cinema and 2 20" cinema displays. Plan is to mount them portrait, landscape, portrait.

I planned to leave the card flashed so I bought two apple mDP to slDVI adapters only to find it doesnt work. I need an active adapter. Before it worked because the 27" LED was native DP I guess.

Question: will it work with just one active adapter or will I need 2?
Does question above depend on whether I use 2 dvi (unflashed) plus 1 adaptors or 1 dvi plus 2 mDP to DVI adaptors (1 or 2 active)?

Question: Which ports are supposed to give boot screen on flashed card?