MP 1,1-5,1 RAM Slots not Working on Mac Pro 4,1

[KingCornWallis]

I have a Mac Pro 4,1 (flashed to 5,1) Dual CPU Tray and booted it up after being in storage for the last 3 months to find that Slots 3 and 4 of tray are not working; RAM installed in these slots are not detected by macOS.

It is my understanding that slots 3 and 4 are connected, and if one is defective the other won't work.

I am using 8 sticks of Hynix 16GB 1333MHz ECC HMT82GV7MMR4A-H9 D8 AB

Here is list of troubleshooting attempts conducted

1. PRAM/SMC Reset
2. Compressed Air in the two sockets
3. Swapping in different working sticks into the slot(s)

Here are some further troubleshooting details:

1. With Sticks in Slots 3 & 4, LED's DSD710 and DSD711 light up
2. With Stick in Slot 3 LED DSD710 lights up
3. With Stick in Slot 4, no LED lights up

Here are my possible diagnosis's, though I am still uncertain why this issue appeared out of nowhere.

1. Bad CPU/CPU Installation
2. Bad RAM Slot(s)
3. Faulty 5,1 Flash installed

Please help.

 

[tsialex]

I have a Mac Pro 4,1 (flashed to 5,1) Dual CPU Tray and booted it up after being in storage for the last 3 months to find that Slots 3 and 4 of tray are not working; RAM installed in these slots are not detected by macOS.

It is my understanding that slots 3 and 4 are connected, and if one is defective the other won't work.

I am using 8 sticks of Hynix 16GB 1333MHz ECC HMT82GV7MMR4A-H9 D8 AB

Here is list of troubleshooting attempts conducted

1. PRAM/SMC Reset
2. Compressed Air in the two sockets
3. Swapping in different working sticks into the slot(s)

Here are some further troubleshooting details:

1. With Sticks in Slots 3 & 4, LED's DSD710 and DSD711 light up
2. With Stick in Slot 3 LED DSD710 lights up
3. With Stick in Slot 4, no LED lights up

Here are my possible diagnosis's, though I am still uncertain why this issue appeared out of nowhere.

1. Bad CPU/CPU Installation
2. Bad RAM Slot(s)
3. Faulty 5,1 Flash installed

Please help.

#1 or #2, #3 is not related to memory slots not working. Most probable is #1, also look for oxidation on the Xeon contacts and bent pins on the CPU socket.

If was #3 your Mac Pro wouldn’t boot.

 

[mattspace]

I have fixed red light on RAM slots, which seems to depend on where RAM is installed, with a Real Time Clock reset (and from storage, maybe battery is dead?), which is a thing you haven't tried yet;

Real Time Clock (RTC) Reset

The Real Time Clock (RTC) is a chip on the backplane board that controls the date and time functions of the computer. If the computer is experiencing an issue booting, resetting the RTC may resolve it. Follow these steps to reset the RTC:

1. From the Apple menu, choose Shut Down (or if the computer is not responding, hold the power button until it turns off).
2. Unplug the AC power cord.
3. Remove the battery for at least 20 seconds. You may need to remove a PCI Express card to have access to the battery.

Alternatively, you can reset RTC by pressing the RTC reset button (small button located next to the battery). Press the button for one second when the computer is shut down but still connected to AC power.

 

[KingCornWallis]

I have fixed red light on RAM slots, which seems to depend on where RAM is installed, with a Real Time Clock reset (and from storage, maybe battery is dead?), which is a thing you haven't tried yet;

Real Time Clock (RTC) Reset

The Real Time Clock (RTC) is a chip on the backplane board that controls the date and time functions of the computer. If the computer is experiencing an issue booting, resetting the RTC may resolve it. Follow these steps to reset the RTC:

1. From the Apple menu, choose Shut Down (or if the computer is not responding, hold the power button until it turns off).
2. Unplug the AC power cord.
3. Remove the battery for at least 20 seconds. You may need to remove a PCI Express card to have access to the battery.

Alternatively, you can reset RTC by pressing the RTC reset button (small button located next to the battery). Press the button for one second when the computer is shut down but still connected to AC power.

Thanks, put in a new 2032 battery but it did not help.

 

[KingCornWallis]

#1 or #2, #3 is not related to memory slots not working. Most probable is #1, also look for oxidation on the Xeon contacts and bent pins on the CPU socket.

If was #3 your Mac Pro wouldn’t boot.

Took a look at the CPU's and sockets...some corrosion one one of the CPUs, and some dust in one of the sockets. Cleaned and reinstalled. Got an additional LED light; the problem was quite clear now.

Tightened all of the Hex Screws further and all 128GB of RAM returned. Thanks

 

[mode11]

If the pressure on the CPU is not sufficient / even, the pins won't make proper contact. RAM channels not showing up is a classic symptom of this. As you've got an upgraded dual-processor 4,1, you've presumably gone from lidless CPUs to regular ones. If so, you'll have been careful when torquing down the heatsink bolts, and perhaps were just on the edge of sufficient pressure (before it went into storage).

 

[KeesMacPro]

you've presumably gone from lidless CPUs to regular ones.

IMO this could be caused by several things:
- insufficient/uneven pressure
- thermal glue residu on the CPU
- dirty plastic spacer

 

[KingCornWallis]

If the pressure on the CPU is not sufficient / even, the pins won't make proper contact. RAM channels not showing up is a classic symptom of this. As you've got an upgraded dual-processor 4,1, you've presumably gone from lidless CPUs to regular ones. If so, you'll have been careful when torquing down the heatsink bolts, and perhaps were just on the edge of sufficient pressure (before it went into storage).

Nope, I went from lidless to lidless again. When I was taking the heatsinks off to investigate, tension was clearly insufficient on some of the screws. I am very hesitant to screw these down hard from what I have read, so I try to do it by feel.

 

[mode11]

Nope, I went from lidless to lidless again. When I was taking the heatsinks off to investigate, tension was clearly insufficient on some of the screws. I am very hesitant to screw these down hard from what I have read, so I try to do it by feel.

If you installed lidless CPUs, there's no need to be hesitant. Obviously, don't go crazy, but with any reasonable amount of tightening there's no need to be worried - the mounting hardware is designed to seat everything properly.

You only need to be super careful if you use lidded CPUs, since you're then able to exert a lot of force on the socket. The heatsink in that scenario makes no contact with the structure surrounding the CPU, so there's nothing to stop it bearing down.