MP 1,1-5,1 Mac Pro 4,1 flashed to 5,1 Chimes but no boot

[Fastsavage]

Ok,

So I have a friends Mac Pro 4,1 flashed to 5,1 running OCLP and can't remember to OS version.

He had a sparky working at his house who tripped a fuse and shut down the Mac (that was running obviously)
Now it will not boot.
We get the chime then just a white screen.

So far I have:
PRAM reset
SMC Reset
Replaced the CMOS Battery
Safe Boot
Recovery

5v STBY light comes on
PSU PWROK light comes on

Pressing the SYS DIAG button and
Found the GPU light was not coming on with a flashed Graphics Card (Sapphire PULSE Radeon RX 580 8GB GDDR5) but does with a GT120
EFI light does not come on

So probably a bootrom issue?

Any other ideas would be helpful please..

Cheers

 

[tsialex]

Found the GPU light was not coming on with a flashed Graphics Card (Sapphire PULSE Radeon RX 580 8GB GDDR5) but does with a GT120

GPU_OK LED requires an AppleOEM GPU to lit and does not work with PC GPUs.

EFI light does not come on

If you have a MATT card, test with it installed and see if you can boot.

If not, then you can try the NVRAM bypass / Firmware Fail-safe Mode - if you can boot, you gonna need the BootROM reconstruction service.

NVRAM bypass / Firmware Fail-safe Mode with Mavericks:

1. With a working Mac Pro, install Mavericks to a previously nuked SATA drive, you can download it from here:
   
   Mavericks Forever
   You can also use other Mac models to create the Mavericks disk, but if you have a Mac with NVIDIA southbridge, like Macmini3,1/4,1, MacBookPro5,5/7,1 and several other from 2009 and 2010, the disk will not work with the Mac Pro. If you only have one of these, do not install the SATA disk internally, connect via USB case. This incompatibility caused a lot of headaches in the past.
2. Go to the defective Mac Pro and disconnect the mains power cable from the PSU, wait a minute,
3. Remove all PCIe cards, install a real AppleOEM GPU from 2008 to 2012 (HD 2600XT, 8800GT, Quadro FX 5600, GT120, HD 4870/5770/5870).
4. Install the Mavericks SATA drive to the defective Mac Pro on SATA bay 1, remove all the other disks, disconnect the power/data cable from the ODDs (this is important, frequently overlooked failed DVD drives block the POST).
5. Uninstall the RTC battery from the holder with a lot of care to not break the positive terminal,
6. Wait at least 20s, then with the RTC battery still uninstalled, connect the power cable and see if you can boot the Mavericks disk.

Without the RTC battery installed, the Mac Pro enters a firmware fail-safe state where the NVRAM volume is ignored (also completely bypassing all the adverse effects of cross-flashing).


Notes:

• Mavericks is the last macOS that still boots, and more or less still work, with the Mac Pro while in Firmware Fail-safe Mode.
• You can try Snow Leopard to Mavericks, but Mavericks is the earliest macOS release that standard ROMTool/flashrom works and you gonna need it to dump the BootROM.
• A lot of EFI modules are ignored by the Firmware Fail-safe Mode, like the problematic APFSJumpStart, you won't access any APFS disks for two reasons - no APFS support from the firmware and no APFS support with Mavericks.
• Some other things also do not work (like BT devices) or work very poorly (like Wi-Fi, requires the RTC to be working to authenticate to WPA networks) - use wired KB/mouse and Ethernet instead.