[November 2024] Last year I acquired a Mac Pro 2006 (A1186). It was seemingly in full working order besides a couple of minor issues/gripes (the case had some minor damage seemingly from being placed down too heavily, and the one remaining optical drive couldn't get past the failing to retract door).

The system was not only supplied to me with a whopping 32GB of RAM but a full compliment of hard drives (4) (4TB in total), but I elected to sell those drives off and I cloned the main system drive to an SSD*. Ultimately though, I wanted to install a variant of Linux of this system**, and have Einstein@home running on the dual Xeon CPUs.

I failed to get the Mac to boot from my USB drive so I swapped in an SSD that I had previously installed Ubuntu on in another computer. The Nvidia GeForce 7300 GT didn't like the desktop environment though and appeared glitchy so I proceeded to download and install a couple of others to try. During the process however the system abruptly crashed and then would no longer start up or chime.

Up until this point I had occasionally had to reseat the RAM trays and in doing so I found them to be quite warm. After much troubleshooting however, followed by some (not so easy) dismantling, I suspected one of the Xeons had perhaps failed as there was a lot of dust built up in the heatsinks which was not obvious from the outset due to the rest of the system appearing clean.

Some things I had tried:

- Reading the DIAG_LEDS [link]: Only Standby (Trickle Pwr) and Power Good LEDs lit when I pressed the button, none of the ones relating to CPU temps, but I'm suspecting the CPUs have been struggling under high temperatures for a while but perhaps not tripping the high temp cut-off while in my possession.

- Clearing the CMOS/replacing the battery.

Dismantling:

Gaining access to the CPU heatsinks took much effort and head-scratching.

Firstly, there are two noticeable variants:

Mine is the left, notice the different RAM bays (lower-right)

Secondly, take note of the 5 labelled screws in the image below, the lower four to be removed after removing the RAM trays (and ideally the graphics card):

The lowest two screws posed a problem for me (and researching online indicated I'm not the first to encounter this); the screws had been installed with thread lock and thus the heads stripped out when I tried to remove them. To overcome this I used my not-a-Dremel tool to cut slots into the heads, being careful to vacuum up any metal particles). I was then able to use a slotted screwdriver to remove the screws (the standoffs below might come out with them). It took care and patience.

With the screws removed and the three shrouds loose, the left most one housing the front fan can be tugged out (it takes some force so just make sure you have removed that single screw holding it down. If you just wanted to gain access to the front fan and to clean the dust built up at the front of the CPU heatsinks (highly recommended***) you could probably get away with only removing that one screw and tugging out the housing.

If you want/need to remove the CPU heatsink towers then you will need to tug off the cover of those. A long (20cm) hex/torx driver will be required to reach in to the 8 screws. Technically a 3mm(?) hex driver is required but T15 (torx) drivers of the necessary length appear to be more available/cheaper and can do the job.

There is temperature probe attached to the base of each heatsink so be sure to unplug those from the mainboard before lifting out the heatsinks. Also make note of which heatsink is which as there are rubber pads on certain sides.

I tried a few other things at the stage to try and coax some more life out of my system while I awaited delivery of a pair of replacement CPUs, but with no luck.

I'm was suspecting (hoping) I had a dead Xeon (rather than some other fault I am not able to pinpoint or fix). Since mine are only dual-core 2.0GHz variants I would have liked to take this opportunity to swap these with a pair of quad-core ones. They need to be LGA 771 versions and according to ChatGPT there are only a few CPUs that are drop-in replacements. Since there were limited options, I went with the cheapest and thus lowest spec I could find, a pair of Quad Core E5320 @ 1.86GHz.

I swapped these in and reinstalled the now dust-free heatsink towers and powered on... the system chimed! Yay.

However... I then powered down the system, connected my SSD and switched it back on... and... no chime. The fans went into "panic mode" and that was it, once again I couldn't get the system to start up.

So what had gone wrong, or what had I done wrong? Ideas:

• There is some other fault and that it worked once was just a hiccup (I hadn't tried the system immediately prior to putting the replacement CPUs in.
• I didn't renew the thermal paste for this brief period of testing; did the replacement CPUs immediately fail because of this? (this seems unlikely)

Options:

• Give up and sell the system on as spares or repairs
• There are some replacement mainboard & CPU bundles, but what if my system's PSU is the issue and causing CPUs to fail? The system isn't really worth spending more money on but I don't like the "what if?"

Other stuff:

*In order to properly mount my SSD in the original caddy/sled I will need a suitable 3.5" to 2.5" bracket that positions the SATA sockets in the same place as on a hard drive.

**I'm still wondering how I might boot the system from a USB drive... Which Linux distro should then use? I prefer to keep the desktop environment as Mac-esque as possible.

According to ChatGPT (which has helped me with CPU options), this Mac is equipped with a PSU rated at 980W - I'm hoping this is accurate and I can perhaps tap into this to provide power for a more modern graphics card.

***ChatGPT also told me that my current CPUs have a TDP of 65W each. If I've had one fail due to the build up of dust discovered in the heatisinks, this doesn't actually bode well for a pair of quad-cores which would have a TDP of 80-120W each and thus a greater heat output... I'll just have to periodically check those heatsinks!