iMac 2011: Recent GPU for iMac 2011 needed; flashing? (replacing failed 6970m)

[richardhancock]

Interestingly, I think that the external display port which does work is currently set as the Master Display as the login screen when booting displays on the secondary monitor. I then have to change it with the software on the Mac to be the second screen, whereas usually the iMac display as always defaulted as master. Does this mean that the external port that works (and is real DP) is the first display port listed in the DCB table that you sent me?

If so it narrows it down slightly before I reflash..

When you talk about 'Active' Displayport is this TMDS? So if i change all of the connectors to TMDS?
I do believe that for the external connections on the iMac, they are using active adapters after Internet Research. The 2011 iMac allows the only a thunderbolt (not Displayport) cable to also be used as an input for a MacBook etc. Displayport to VGA \ DVI \ HDMI should work as outputs on all ports however.

https://support.apple.com/en-gb/HT202214
https://www.tekrevue.com/tip/ins-outs-imacs-target-display-mode/

I believe that one of the ports at least goes through a thunderbolt controller with I/0 which means its not a normal kind of connection.


With the DCB, for example with Connector 3 (D6 5F 01 08 20 00 42 0F) which is type 0x6 (DisplayPort) which is supposed to be enabled, right, it has OF at the end which i thought meant it was disabled? Sorry if I sound stupid, I have got rather confused !! Also the ones listed in bold underneath the chart, are these the display port ones or the disabled ones or DisplayPort? I couldn't find those hash's listed underneath each connector in the chart!

[Fl0r!an]

Interestingly, I think that the external display port which does work is currently set as the Master Display as the login screen when booting displays on the secondary monitor. I then have to change it with the software on the Mac to be the second screen, whereas usually the iMac display as always defaulted as master. Does this mean that the external port that works (and is real DP) is the first display port listed in the DCB table that you sent me?

I actually never verified if the order of DCB entries equals the order of priority in OS X, but that might be true. I don't think that the first DP in the DCB table is necessarily your working external port, it might also be an port #2, while the internal one could be port #3 or #4 (just theoretically, might be different).

When you talk about 'Active' Displayport is this TMDS? So if i change all of the connectors to TMDS?
I do believe that for the external connections on the iMac, they are using active adapters after Internet Research. The 2011 iMac allows the only a thunderbolt (not Displayport) cable to also be used as an input for a MacBook etc.

I think you're mixing some things up. "Active DP adapters" are special adapters, which work as real DisplayPort device (they're needed for resolutions beyond 1080p or for multi-screen setups on AMD GPUs). Passive DP adapters are the usual ones which e.g. Apple is selling; they just passively pass through a TMDS signal which is generated by a "real" DP port as soon as it recognizes a passive adapter (instead of an active adapter or an real DP device).

And yes, the DP connectors somehow have to be routed through an Thunderbolt controller, but I guess (well, I hope) we won't have to care about that...

With the DCB, for example with Connector 3 (D6 5F 01 08 20 00 42 0F) which is type 0x6 (DisplayPort) which is supposed to be enabled, right, it has OF at the end which i thought meant it was disabled? Sorry if I sound stupid, I have got rather confused !! Also the ones listed in bold underneath the chart, are these the display port ones or the disabled ones or DisplayPort? I couldn't find those hash's listed underneath each connector in the chart!

Sorry, I should have explained that: The byte order is reversed, so the connector type is here: D6 5F 01 08 20 00 42 0F
So you just have to touch the 2nd half of the first byte, nothing else.

[Rominator]

encouraging progress !

keep up good work

don't forget "0E" is supposed to stop loading further dcb entries, I have seen it in Mac BIOS before when a PC port isn't used

[richardhancock]

Right, done many flashes this evening  

I started off by changing the ROM so that each displayport with 6 in the second half of the first byte was changed to TMDS. (As well as keeping the corresponding TMDS) This displayed nothing on the screen on any monitor (Internal or External), so I don't think that any are 'Active' ports.
I then went through each one by one and enabled each one.

I have figured out that:
DF 5F 01 08 20 00 42 0F (NOTHING ON ANY PORT) (HAVE DISABLED)
C6 4F 01 08 10 00 42 0F (EXT DISPLAY 1)
BF 8F 03 04 10 00 42 0F (NOTHING ON ANY PORT) (HAVE DISABLED)
A6 7F 02 02 10 00 42 0F (IMAC INTERNAL DISPLAY)

I then tried just the two ports that wouldn't work on anything as TMDS (thinking they might be combined or something) and still nothing on 2nd thunderbolt / DP output.

I still cannot get the second thunderbolt port working. So I think it must use another kind of protocol apposed to DisplayPort or TMDS? Do you think that this could be a special thunderbolt port input? I was going to try LVDS and VGA as the protocol but I didn't think this was necessary?

If I simply cut and paste the iMac code above the EXT Display Port 1 will this make it master?

Regarding the EFI is it better if i'm using the UEFI designed BIOS for this card or the standard? I'm currently using standard!

Thanks for your help

[Fl0r!an]

You shouldn't set the "type" to anything else than "0xF" (-> disabling it) or it's original value (0x6 or 0x2). Configuring a DP port as TMDS (0x6 -> 0x2) shouldn't get you anything.

You seem to have found the 2 port definitions which enable your internal display and one of the TB ports, which is already a great first step!
The corresponding TMDS definitions (-> TMDS signal assigned to the same connector index, usually the line below) should also be enabled to retain the functionality of passive DP adapters.

To (partly) enable the 2nd DP port, you should now start re-enabling all other TMDS ports, one by one. One of them should enable your VGA adapter.
I'm quite sure this will do it, since that DP port was working with the original BIOS. I also think that it's one of the TMDS ports at the top of the list, but that's just a guess.

It shouldn't matter a lot if you're using the UEFI BIOS or the standard one as the UEFI will be overwritten anyway.

Good luck!

[richardhancock]

Thanks! 

I have now gone through and enabled each TMDS port, and have got no picture every time I did this in order and now have them all enabled. Is this the right thing to do or should I enable one and then disable it again and move onto the next one? My table now looks the same as the original but with the LVDS disabled. I also tried enabling VGA at the bottom just to try!

Do you think that this is an incompatibility with the Graphics Card and the second port or a complication with Thunderbolt? The only other thing i thought is I might have damaged the port somehow or this port can only be used with DVI or HDMI Adapters?

Right ok, if the 680 mac edition from the Mac Pro uses display ports, should the EFI be fairly similar?

[Rominator]

Anytime you have a DP port that works, you should enable the next port in list, this is usally a TMDS port that is a DVI legacy output on the same port.

Could be the second TB port needs to chat via this.The DCB should look like DP port, then the legacy port on same wires, then next DP port, etc.

[Fl0r!an]

Just to make sure we understand each other: The port you're just trying to enable was working with the original VBIOS through an DP->VGA adapter, right? That port got disabled when we threw out all TMDS / LVDS / VGA ports, and you want to re-enable it.

Sounds very surprising to me that you can't enable a port again which was working formerly, so I guess I'm missing something.

[richardhancock]

Hi Rominator, thanks for your reply. Have made sure of this when I was doing it. I have just gone back and tried a couple more times with only each one of each unidentified DP enabled each time and still no luck with the last remaining TB port. Also tried the remaining TMDS ports and still nothing.
I have gone back to all DP corresponding TMDS being enabled with nothing else for Mac OS X.

I have a feeling that possibly the port is working but just not with the VGA version of the adapter. People on other forums where saying when they have done similar upgrades with this iMac and NVIDIA cards that they had to swap to a HDMI / DVI version or VGA for their external monitor to work.  I know in my experience with PC's that graphics cards only allow one VGA output a lot of the time.


Florian, Sorry I think we misunderstood each other, my mistake for not trying both ports when I first installed the card, but it never worked even with the original Dell BIOS, I have reflashed it back to confirm. With only having the one monitor I just plugged it into the first port I saw. So I don't think its to do with the routing? Has to be it not liking the VGA adapter in this port. I have a friend who has a HDMI version which I should hopefully be able to try in this port. I have a feeling this might work. Have confirmed on Dell forums that the 660M works with multi external DP so the card does support it, but nobody seems to have mentioned trying a VGA in all ports, only 1x VGA and then 1X HDMI etc.
Also put the original 6770M back in and port then works, so the port itself is fine.

[Fl0r!an]

Okay, so the 2nd DP port isn't even working in Windows with the original BIOS? I'd also try a different type of adapter, but I guess that port just isn't connected to the right outputs on your GPU.

I'll add the 680 Mac Edition to the ROM as soon as I can (Friday or Saturday). Be aware that it might prevent your iMac from booting (if it really doesn't like it...), so you'd have to do this: http://netkas.org/?p=1182

[richardhancock]

No not with original BIOS I should hopefully be able to try adapter tonight or tomorrow.

That would be great if you could! Having the EFI attached would make it perfect. The only thing that worries me is it says about it only working if you have a second card installed? Also EEPROM size, Im not sure how to check!

[Fl0r!an]

You should be able to restore in Windows through VNC, without additional GPU.

I also think that it's unlikely to end that bad. 2011 iMac EFIs are known to work in cMP, so I guess / hope the same applies the other way around.

[richardhancock]

Right ok, thats good news! Yes definitely sounds hopeful if thats the case. The EFI between the 660 and 680 should be relatively similar as well hopefully! 
Thanks

[Fl0r!an]

Alright, I attached the (only slightly modded) GTX 680 EFI to the 660M UEFI ROM (didn't use the non-UEFI one because it has a strange structure - security cert is within VBIOS section, not sure if this is a bug?) and PM'ed it to our brave guinea pig (no interest in feeding the eBay guys).

The good news: It does NOT produce a brick and shows something at boot time on internal screen!

The bad news: The boot screen is scrambled:



A simple PRAM reset might fix it, but I think there's a bigger issue. Maybe the Mac Pro EFI doesn't support the internal DP connection? Or Apple customized it somehow?

[richardhancock]

I have now done a couple of extra tests!

Done PRAM reset.

No scrambled image on the external screen (still remains on iMac internal), just a very slight flickering with the normal loading bar. I think somehow the iMac DP needs to be set to be the master display. Shut down fine (bit slow) with normal swirling.

Its detecting the iMac internal display as a cinema display so no brightness controls!