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azranath

macrumors newbie
Original poster
Aug 19, 2023
4
0
hi all, new here, does anyone have a link to what the diagnostic led's in a mac pro 4,1 mean? i'm having problems with mine, in that i get a green light and amber light at the top 2 lights, a solid green in the next bank, but then it goes through the next few lights, than just keeps repeating that sequence.
I don't get a picture,no chime but the fans are normal, i tried a different cpu tray and changed the cpu a few times but with no luck, can anyone help with this? i#ve looked everywhere i can think of, but i can't seem to get an answer to this issue
Many thanks in advance if you can help me with this
 

tsialex

Contributor
Jun 13, 2016
13,454
13,601
See the Apple Technician Manual, pages 28 to 38 have the full description of the Diag LEDs.

If you don't have EFI_DONE lit, you have a brick. From what you describe, it's probably one.
 

tsialex

Contributor
Jun 13, 2016
13,454
13,601
There are two banks of LEDs, the first bank LEDs are:

  • OVTMP CPUA (RED)
  • OVTMP CPUB (RED)
  • PSU PWROK (AMBER)
  • 5V STBY (AMBER)
  • 3.3V (AMBER)
  • 1.5V (AMBER)
  • 1.05V (AMBER)

The second bank LEDs (not all PCBs pads have LEDs installed, just the three below) are:
  • SYS_PG, (AMBER)
  • EFI_DONE (GREEN)
  • GPU_OK (GREEN)

If you don't have EFI_DONE lit, you can't boot at all, but even if EFI_DONE LED is lit, the BootROM could be corrupted in a way that you can't boot.
 

tsialex

Contributor
Jun 13, 2016
13,454
13,601
This will reset a lot

It's not a reset, nothing is modified inside the BootROM, it's just temporarily NVRAM bypass.

When the PEI detects that the battery is not present on the backplane RTC battery socket, the NVRAM is completely ignored for the current initialisation/POST process.

If the OP can boot without the RTC battery and the Mac Pro stops booting again with the RTC battery present, it's confirmed that the NVRAM is corrupted (EFI_DONE off already indicates it). This will be relative good news, also a more economical repair requiring just a replacement BootROM or a MATT card.
 
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azranath

macrumors newbie
Original poster
Aug 19, 2023
4
0
many thanks for the replies, i've looked into both solutions and will try and work out a solution, but with my rubbish eyesight it could be easier buying another mac :)
 
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