iM 4,1-14,4 EnableGop: Pre-OpenCore GOP support for EFI-era iMacs and Mac Pros

[jaksemasch]

But there are obviously 2 EFI signatures 0E F1 (read from right to left - little endian).
The enableGOP-patched vBios shows one at offset 67584 (byte) and the other at 81920.

It's confusing to make heads and tails here due to the right to left reading, which afaik also applies to reading the file. Hence the first image, telling from the end of the data, is actually the last image and appears to be enableGOP. If the notion is correct, that the last image takes precedence, than this could explain why the Mac boot screen works, but PC GOP is a miss. Unless enableGOP is PC compatible, how can this possibly work?

Why even bother to have 2 GOP images in the file, if only one is used? I must also admit that I do not understand the swapping of the original NPDE header and image length. Could there be some confusion in the order?

How is this supposed to work, say if I want to install enableGOP myself?

I don' t see the difference in patching any of the vBios files that won't show a VGA boot screen after the enableGOP patch, compared to those that do.

 

[BadAxe80]

Hi,
I have a MacVidCards flash Sapphire RX580 which is not giving a boot screen on a EnableGOP flashed MP5,1.
I get display once it loads Mojave. I understand this can happen. However, it also won't load Sonoma with OCLP. I dont get the OCLP boot screen and it actually just boot loops.

So basically, if I backup the firmware of the MacVidCards RX580 and flash it back to stock, can I go back to the MacVidCards rom later if I need to? Will a ROM dump capture everything it needs? and will flashing the stock rom remove all trace of MacVidCards tinkering? I have access to a PC for flashing.

Realistically, with EnableGOP I'm unlikely to ever need the MVC rom again but I don't like to burn my bridges.

Thanks

I can't believe I missed the most obvious solution. Flick the dual bios switch!
Done and all working now.

 

[Bmju]

But there are obviously 2 EFI signatures 0E F1 (read from right to left - little endian).
The enableGOP-patched vBios shows one at offset 67584 (byte) and the other at 81920.

They are EFI drivers. They are all loaded, in the order they appear in the ROM. The GOP driver, which needs to be in the card for it to work with (U)EFI at all, is what was in there anyway. EnableGop is a driver to run some code from OpenCore, which modifies how GOP is set up to get it into the very specific format of GOP which is all that will work with Apple.

 

[Borowski]

Why even bother to have 2 GOP images in the file, if only one is used? I must also admit that I do not understand the swapping of the original NPDE header and image length. Could there be some confusion in the order?

Not every present image is mandatory and will be executed by host hardware.
For example, some modern cards (i found it on AMD Navi and up) have 2 UEFI GOP-images, one for x86- (code type 0x8664) and one for ARM-architecture (0xAA64).

NPDE-string in EnableGOP-header seems to be needed to avoid "invalid firmware image"-error with nvflash: https://forums.macrumors.com/thread...om.2388570/page-2?post=33530665#post-33530665
If you program with SPI, it isn't not needed and it works, i "forgot" it as i'm doing mods with hex-editor and it worked anyway. So it is only nvflash restriction.

 

[jaksemasch]

They are EFI drivers. They are all loaded, in the order they appear in the ROM. The GOP driver, which needs to be in the card for it to work with (U)EFI at all, is what was in there anyway. EnableGop is a driver to run some code from OpenCore, which modifies how GOP is set up to get it into the very specific format of GOP which is all that will work with Apple.

Image or driver, are these different words for the same thing?

When using GOP_Updater, it usually shows:
EFI is NOT last image! Fixing ID, last-image bit and checksum for EFI image.

Why bother with "last image" logic?

When I analyze an original vBios or vBios processed by GOP_Updater, I can only see one GOP section (55 AA .. F1 0F). After the enableGOP insert, I see 2.

You wrote: "they are all loaded in the order they appear in the ROM". Considering the little-endian architecture, I suppose that means first becomes last. I would think that whatever drivers loads last prevails, which I suppose should be the EnableGOP driver, hence the original GOP image or driver is out of the picture, or not?

After inserting the EnableGOP driver, which has apparently been designed to work for a Mac Pro, I therefore conclude that the card will no longer work with PC/UEFI. Is this correct?

 

[jaksemasch]

Not every present image is mandatory and will be executed by host hardware.
For example, some modern cards (i found it on AMD Navi and up) have 2 UEFI GOP-images, one for x86- (code type 0x8664) and one for ARM-architecture (0xAA64).

NPDE-string in EnableGOP-header seems to be needed to avoid "invalid firmware image"-error with nvflash: https://forums.macrumors.com/thread...om.2388570/page-2?post=33530665#post-33530665
If you program with SPI, it isn't not needed and it works, i "forgot" it as i'm doing mods with hex-editor and it worked anyway. So it is only nvflash restriction.

That sounds reasonable, but how does the system know which GOP-image (or driver?) to use? Isn't this managed by the PCIR (PCI Configuration Information Record), beside containing vendor and device ID, indicating where images are located in the vBIOS and which mode to use? My understanding is, the system's firmware (BIOS/UEFI) is responsible for interpreting the PCIR. The PCIR structure may include a "last image" bit, which indicates whether additional images follow. If multiple PCIR entries are present, the firmware prioritizes the last valid entry based on this bit.

If there are multiple NPDE (NVIDIA PCI Data Structure Extended) sections, doesn't there need to be some logic or rational which one will be used?

 

[jaksemasch]

Anyway, I suppose there are some compatibility issues. For example, enableGOP 1.4 only works after GOP_Updater. Perhaps due to the last image bit set by GOP_Updater? From what I understand, vBiosInsert seems to swap the order of the original GOP and enableGOP, while retaining the header, but I'm not sure. Depending on the original vBios, enableGOP 1.1 seems to break the PC part, but it's not that anything seems wrong with the original vBios.

 

[fhturner]

Hey Everyone—

Been a minute since I've done much w/ my Mac Pro 5,1s. I'm working on injecting EnableGOP into the Boot ROMs. Actually, I've done that part on 2 of them, and it seems I'm having trouble w/ a Sapphire Pulse RX 580 that still won't show a boot screen/picker. I bought the 580 years ago new (AFAIK). Is there something else I need to do to fix or troubleshoot? I've looked but cannot find the Gaming/Compute switch on this one. I've got a Biostar Gaming RX 550 that works just fine in the other Mac Pro after the "EnableGOP enabling", and the machine with the 580 does show the boot screen too if I swap in a spare RX 550 for the 580. So it seems like the 580 is the problem here. Thanks for any suggestions!

 

[Borowski]

Check if active gpu-bios has UEFI.
If yes, the BIOS may have been modded. This will break signature and deactivate GOP functionality. Check techpowerup for a marching bios.

 

[fhturner]

Check if active gpu-bios has UEFI.
If yes, the BIOS may have been modded. This will break signature and deactivate GOP functionality. Check techpowerup for a marching bios.

Okay, thank you. I have been pulled away from the office where I have this machine, but will investigate further when I get back there. I bought the card new, so I would hope it hasn't been modded.

I'm not very up on looking at GPU firmware and BIOSes...can you point me to a good reference (or if there's a post in this thread) on what tools to use and how to check?

Thank you!

 

[fhturner]

I'm not very up on looking at GPU firmware and BIOSes...can you point me to a good reference (or if there's a post in this thread) on what tools to use and how to check?

I have tested this RX 580 in a second Mac Pro w/ working EnableGOP boot picker screen, and the RX 580 still does not show any screens prior to the login window.

So, what do I do to "check if active gpu-bios has UEFI"? I've searched "gpu-bios" in this thread, but have not found any particular instructions about how to look. Can someone please point me in the right direction?

 

[Macschrauber]

I have tested this RX 580 in a second Mac Pro w/ working EnableGOP boot picker screen, and the RX 580 still does not show any screens prior to the login window.

So, what do I do to "check if active gpu-bios has UEFI"? I've searched "gpu-bios" in this thread, but have not found any particular instructions about how to look. Can someone please point me in the right direction?

As a role of thumb: if OpenCore (Legacy Patcher) displays the OpenCore boot menu, the GPU's vbios GOP is valid.

If it is invalid and displays no OpenCore menu, there is an option in OCLP Patcher app: preload nvidia / amd gop. If its displaying the OpenCore boot menu after this tweak, the GPU's vbios GOP is invalid.

This changes nothing with the native boot picker, but is a diagnose step.

If a GPU's vbios is invalid, some needs to find the unaltered original vbios. Also check out a bios switch, some have original and tweaked bios selectable.

 

[fhturner]

As a role of thumb: if OpenCore (Legacy Patcher) displays the OpenCore boot menu, the GPU's vbios GOP is valid.

If it is invalid and displays no OpenCore menu, there is an option in OCLP Patcher app: preload nvidia / amd gop. If its displaying the OpenCore boot menu after this tweak, the GPU's vbios GOP is invalid.

This changes nothing with the native boot picker, but is a diagnose step.

If a GPU's vbios is invalid, some needs to find the unaltered original vbios. Also check out a bios switch, some have original and tweaked bios selectable.

Ok, thank you! I did this (added the OCLP option to preload the AMD GOP), and was able to get the OCLP picker and boot screen. Without it, I get nothing until the login window.

So the GPU's vbios GOP is invalid. How would that be on a (supposedly) new/unused card? Is there any relatively easy and straightforward way/guide to flash the original vbios? I see suggestions about finding the right one on Techpowerup. Do I have to go "around the world" to accomplish the flash process? Thanks again!

 

[Macschrauber]

Ok, thank you! I did this (added the OCLP option to preload the AMD GOP), and was able to get the OCLP picker and boot screen. Without it, I get nothing until the login window.

So the GPU's vbios GOP is invalid. How would that be on a (supposedly) new/unused card? Is there any relatively easy and straightforward way/guide to flash the original vbios? I see suggestions about finding the right one on Techpowerup. Do I have to go "around the world" to accomplish the flash process? Thanks again!

Check twice, if you don't got a bios switch. That darn thing is really tiny. If it is set to computing, you got the culprit.

 

[Macschrauber]

I need a confirmation with MVC / MacVidCards flashed RX580:

a) EnableGop in the Mac Firmware prevent those cards from booting native MacOs [yes/no]
b) EnableGop in the Mac Firmware prevent those cards from showing OpenCore boot menu [yes/no]
c) Those cards are not showing OpenCore boot menu in original Mac firmware [yes/no]


are there workarounds for MVC RX580 GPUs, when using OpenCore?