MP 1,1-5,1 Mac Pro 2,1 Powers On but No POST, No Chime, No USB — EFI_GD LED Lit

[Hil_]

I’m troubleshooting a Mac Pro 2,1 (Late 2007, 8-core) where the CPU sockets are soldered directly to the main logic board — so there is no separate CPU tray like in the standard tower model.

The system powers on via the front panel button and can be forced off with a long press. However, it shows:

• No chime
• No video output
• No USB response (Caps Lock unresponsive) (though powering the mice red light)
• No HDD activity

Already replaced:

• Power supply (PSU)
• Logic board (backplane with CPU sockets)
• CPUs (both replaced in the sockets)
• Both memory risers and all RAM
• GPU (using known-good Mac-compatible NVIDIA card)
• CMOS battery
• Front panel with power button (edited)

Observations:

• EFI_GD LED lights green after powering on
• TRICKLE LED lights only while holding DIAG or RTC reset buttons
• CPU A/B Overtemp LEDs flash briefly (normal POST signal)
• GPU spins at max fan speed
• USB ports have power, but Caps Lock never lights
• RAM riser LEDs flash once when powering on
• No 5V standby LED remains lit at rest
• No signs of POST continuing beyond EFI

Tested with: Minimal config: only 2 FB-DIMMs in correct paired slots on Riser A, no GPU, no drives — still no chime

Question:

Since EFI firmware loads (EFI_GD LED confirms), but the system halts before USB init, what could still be preventing full POST?

Could this be:

• Bad logic board even after replacement?
• Deep CPU socket issue despite both CPUs and logic board being replaced?
• PSU voltage sag under load? (unlikely...)
• Corrupted firmware/SMC/NVRAM state?

Worth mentioning: prior to this issue, the machine experienced sudden shutdowns (as if the power was cut off). Later, it entered complete silence. I cleaned and replaced all the components listed above, but with no results.

Thanks in advance for any kind of advice!

 

[reader50]

With every major component changed, it's hard to fault any of them. There's not many common elements left.

Are you using the same keyboard / mouse for testing, and were they plugged in during minimal-config testing?

Any secondary boards that weren't changed, like an airport/bluetooth board? (I've never worked on a 2,1)

Is the power cord the same one all along? How about the outlet it's plugged into (or UPS).

 

[Hil_]

thanks for response. Small correction: the power on switch wasn't replaced.

Same keyboard and mouse (Apple) tried front and back panel ports. Caps lock is unresponsive, but mouse sensor (red light) is on.

Airport and Bluetooth cards were removed.

PSU is identical, though i also tried it with the original. Power cord is the same all along.

At the beginning, I assumed the logic board had failed, soi replaced it with no response, after that, the memory modules, then the memory risers, then the CPU (x2) units, and at each step there was no change.

My next step is to detach one of the CPU for each attempt. (I also tried booting without a graphic card and with an ATI card)

I wonder what else I can try...

 

[reader50]

Try a different keyboard and mouse, tested good on another computer. A bad USB device might lock up the boot process - though I'd expect it to muck things up after POST. And try a different power cord for good measure. Desktop Macs typically use office-style power cords. You can borrow one from a printer, copier, etc.

If those don't do it, you're into testing each component in a working Mac Pro.

 

[Hil_]

Thanks, I will give it a try.

 

[dubman99]

I also have the same machine a 2007 8-core which also has a very similar issue. Originally mine started beeping on boot and flashing quickly which appeared as a ram error.
I cleaned the whole thing hoovered the slots out and cleaned all contacts with alcohol.
The beeping error then went away but since hasn't booted up. Interestingly I don't even get the ram error beeps even when no ram or riser boards are inserted which I think is a bit strange.
My diagnostic LEDs are exactly the same as yours except my EFI_GD led only flashes during boot if you're holding down the diag button; it doesn't stay lit. Trickle and Power are OK.
I tried a minimal hardware boot up and it's the same. I even disconnected as much peripheral hardware to the board as possible including the front panel and booted it from the jumper at the top middle of the board. I disconnected as many cables as possible to see if it made a difference. I also did a SMC reset and PRAM reset (my keyboard is also like yours no Caps lock).
Like you I tried the original GPU to see boot and again no response. I removed the processors cleaned them repasted them too and put them back and still the same.
I also tried booting from CDs and where you'd normally hear the CD drive spin up momentarily at boot I don't even hear that and the eject button on the drive itself does not work (it used to before although not always) and my F12 key won't eject it either.
I'm suspecting some kind of faulty EFI. Just now i unplugged the data ribbon on back of CDrom drive and when I started the system I heard it spin. When I plug my ribbon back in no spin. I have also adjusted the jumper on the CD to see if it made any difference but no originally it was set to CS cable select I selected master but it also made no difference.
For yours seeing as you have changed absolutely everything apart from the stuff in the case you could try disconnecting the front panel completely and booting off the jumper perhaps something remaining in your case faulty.
The other odd thing that has happened on mine was after I fixed the ram error beeps I was trying different GPUs and sometimes the GPU present led was lit, other times flashing and now it's off completely. All my diag leds work. Ive also checked the 5v and 12v rails they look alright when idling (havent checked 3.3v... if there even is one). Ive also used a watt meter plug to see what it might be up to it draws 2.4watt when off and 125watt when booting rises to about 130w after a few seconds and then just stops.
I currently have no idea but if i find the answer I'll post it here. Mines been down for about 6 months I've tried about 3 times to repair it now and no luck.

 

[dubman99]

By the way don't mix and match your CPUs - Xeon processors are "Matched pairs" you're not supposed to use them as part of another set someone told me before - im not sure how true that is. I don't know if it's a good idea to mix them ive never looked into it. Also, as previous person mentioned unless you saw your new logic board working it's not impossible for you to have two faulty logic boards but it's a little unlikely.