MP 1,1-5,1 2009 Mac Pro CPU Tray issue

[khronokernel]

TL;DR: My MacPro4,1 was having random cryptography issues, then the CPU tray reported the CPU as missing and refused to boot. After removing the Northbridge heat sink, the machine reports the CPU as alive and well.

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Machine Specs​

MODEL:   MacPro4,1 - Early-2009 (Flashed to MacPro5,1 - 2010)
CPU:     Xeon W3520 @ 2.66GHz 
RAM:     16GB DDR3 1066Mhz (4x4GB)
GPU:     AMD RX470 (RX5700XT tested)
SSD:     WD SN750 1TB NVMe
WIFI:    BRCM94360CD
OS 1:    macOS Monterey (12.0 Beta 4)
OS 2:    macOS Big Sur (11.5.1)
OS 3:    Windows 10

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To give a bit of context, I had bought a MacPro4,1 off Kijiji locally to help out with development of OpenCore Legacy Patcher. The machine was honestly horrid to look inside with the amount of dust, so when I got her home I cleaned her out. When I looked at the CPU tray, I noticed a plastic peg had been broken. At the time I didn't think much of it and so dusted the rest of the machine off and installed macOS Monterey on an NVMe drive.

Later on, I found that this plastic peg was actually one-half of the Northbridge's heat sink.

A couple of days pass and I start getting weird NVMe issues. I believed them to be quirks of the dated 4,1 firmware so decided to firmware flash my machine to a 5,1 in anticipation of a Xeon X5670 I got off eBay (but wouldn't arrive till September). The issues persisted with the firmware flash.

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Main issues​

The main concerns I noticed (in order):

• Firmware failing to see NVMe drive in UEFI
  • NVMeDxe already loaded via OpenCore, flashing to 5,1 seemed to fix the issue
• Trying to let Fortnite (in Windows 10) auto-configure settings would crash the hardware
  • At first, seemed to be the PSU overloaded, however, the issue persisted on other cards
• Booting macOS would fail on cryptography verification relating to the APFS seal
  • This would report on every SSD I installed, including those that boot fine in other machines
• macOS USBs would start to error on mismatched BaseSystems

And finally, the CPU tray lit up reporting "CPU Missing or Overheating", thus resulting in a non-bootable machine. This was quite frustrating as I only had the machine for a week, but the Mac Pro was a tool for OpenCore development and not my daily driver. So I was ready to throw in the towel and put the machine on a shelf to mess with another day.

Cryptography errors	CPU Tray light

I assumed that the CPU itself was dead due to the weird crypto errors, so was going to wait till the new CPU arrived. I then did a lot more cleaning, looking at the socket for issues but to no avail. However, after a bit of discussion with a user on my Discord server, ylluminate, they mentioned an issue with the CPU Tray/Northbridge on one of their 4,1 (flashed 5,1) systems. They opted to replace the whole tray at the time due to time reasons but this gave me an idea, what if the Northbridge has too much one-sided pressure on it from the broken heatsink?

CPU Socket intack	NorthBridge

I followed this up by first removing the chipset heatsink and booting as is. And wouldn't you know, the thing booted! I later threw some zip ties on the heatsink and an abundance of thermal paste to aid with the thermal transfer, as I was afraid any pressure would cause the issues to pop up again.

OpenCore Boot Picker Loaded	macOS loaded

Concluding thoughts​

From this odd situation, it seems the Northbridge became quite sensitive to pressure after the last user had the heatsink broken on one side creating an unbalanced distribution. Zip ties and thermal paste did fix it though how long this northbridge will last is up for debate.

I may in the future invest in a dual-socket CPU tray however seeing the overpriced market on eBay, I might wait till someone wants to donate one for OpenCore Legacy Patcher development ;p

I would be quite curious whether others have experienced something similar with their northbridge, would love to hear other reports.

 

[dataid]

The problem with the broken MacPro Northbridge heat sink retainers is a common problem that occurs as the plastic retainers age. It is the cause of many odd MacPro behaviors. YouTube shows several methods of replacing the retainers with posts, screws with insulation and replacement plastic retainers which can be found on ebay. The important thing is to put in a permanent replacement for the retainers (always replace both) which will assure proper Northbridge temperature. Check to see that the North bridge temperature is in the correct range after the repair and a few days after the heatsink compound has been compressed.

 

[KeesMacPro]

If you still have both original springs you could mount the heatsink with 2 (metal or nylon) screws M3x16mm , nuts and washers .
This is a very effective and permanent solution for the NB rivets issue.
The Delta NB heatsink- diode after a correct repaste should be 12 degrees Celsius or less.

TBH every MP4,1/5,1 I get my hands on, the NB heatsink is one of the first things I do , so unfortunately I cant post any data about the behavior of the machine with unequaled pressure on the NB, i'm sorry ...

 

[Macschrauber]

second that, every Mac Pro 4.1 / 5.1 I get the hands on I service the Northbridge Rivets.

It's one of the standard faults, sometimes the Northbridge is fried on CPU boards and so the board is dead.

 

[tsialex]

Another thing to pay attention with used Mac Pros, the CPU trays that were overheated because of failed heatsink push pin sometimes have the northbridge die so concave, or convex, that in some extreme cases is not possible to use the CPU tray even after the heatsink repair - the delta becomes excessive (greater than the usual 10/12ºC) and the overheat LED appears frequently plus the SMI kernel panics.

A CPU tray that have a damaged die usually becomes a parts donor, it's not cost effective to replace the northbridge, unless someone is doing the replacement job for free.

 

[avro707]

My dual CPU Mac Pro 3.46ghz (2x X5690) was doing under load about 70ºC on the northbridge, but with the fans cranked up a little bit (to 1000rpm) it stays at 60ºC or under.

I was worried about this previously so I took the CPU tray out, cut off the plastic retaining pins and took that Northbridge off and re-did the thermal grease (Arctic Silver 5 now) and secured it again with new plastic pins (the little white ones off ebay):

50pcs PC Heatsink Cooling Fan Spring Rivet Fastener Push Pin Mounting Screw | eBay

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One of the Youtube videos mentioned these had to be shorted a little to fit, that's what I did. Everything seems to be running okay now.

What I'd also mention is the northbridge heatsink is a bit delicate so for anyone working in that area, do so carefully. Don't rush it. It might be worth rigging up a little Noctua fan to cool the Northbridge heatsink as well.

What I also did when applying the thermal grease to the CPUs and the northbridge was to apply a pea-sized amount and a little plastic card to spread it out very evenly. That seems to have brought the CPU temperatures in particular well down in the mid 30ºC range.

The donor computer that gave me the dual-core CPU tray needs new cooling fans - so I'll get those. I also got some brand new heatsinks and fans for the dual core tray which was a big surprise, didn't expect they'd still be around.