Resolved Trying to overcome issues with my dual CPU cMP and RAM slots 1 & 5 not being detected. Help wanted.

[mikeydeezy]

I've spent the better part of this morning trying to explain my question as clearly as possible. I realize the answer to my question might not be known outside of Apple (and overall a pretty pointless question) but I know there are some brilliant minds on this forum who may be up to the challenge.

So I will refer to my two CPUs by the slots they occupy on the daughter board of my Mac Pro 4,1.

CPU A is in perfect condition. Works great. When I run it on the dual tray without CPU B it recognizes RAM slots 1-4 just fine. Fantastic.
CPU B has minor damage on the top left portion of the PCB. It seems to have been damaged in a way that impacts the RAM slots it can "see". It sees RAM slots 2-4 or 6-8 depending on it's position on the tray. I know for certain it is not the board itself because when I replace both chips (x5680s) with the original CPUs (x5570s) all 8 RAM slots are recognized and it's business as usual.

Now of course the real fix to my issue is to just replace the CPU. But outside of not being able to run my 3 sticks of RAM in an optimal configuration CPU B is working just fine for my needs.

My main point and question is this (tl;dr):

I ran CPU A alone in the dual tray. RAM slots 1-4 were recognized. Fantastic. When I added CPU B and booted the machine still saw RAM slots 1-4 just fine. CPU B being added didn't change that behavior at all. This persisted across multiple reboots/shutdowns of macOS. However once I booted into Windows and booted back to macOS slot 1 and slot 5 is no longer recognized as I can only assume CPU B took over.

Is there a way to change how macOS "assigns out" which CPU manages which slots?

 

[Snow Tiger]

Installing damaged silicon in a workstation is foolish . Toss the bad CPU into the recycle bin and go onto eBay . For $40 you can get a replacement X5680 . Indeed , this might be a good opportunity to simply grab a pair of X5677 ( Quad 3.46 GHz ) for just $20 and run your Mac at 8 Cores at 3.46 GHz . I built the first Macs with this configuration and it is still pretty robust .

 

[mikeydeezy]

Installing damaged silicon in a workstation is foolish . Toss the bad CPU into the recycle bin and go onto eBay . For $40 you can get a replacement X5680 . Indeed , this might be a good opportunity to simply grab a pair of X5677 ( Quad 3.46 GHz ) for just $20 and run your Mac at 8 Cores at 3.46 GHz . I built the first Macs with this configuration and it is still pretty robust .

I'm sure you're right. I did a Google search relating to the topic of physically damaged CPUs (from being dropped, delidding gone wrong etc.) and it sounds like some have gotten years of use out of them post accident.

But I will definitely replace this CPU.

 

[Snow Tiger]

I'm sure you're right. I did a Google search relating to the topic of physically damaged CPUs (from being dropped, delidding gone wrong etc.) and it sounds like some have gotten years of use out of them post accident.

But I will definitely replace this CPU.

Oh gosh . You don't need to install expensive delidded ( Integrated Heat Spreader Less ) processors in a factory Dual CPU Mac Pro 4,1 ( 2009 ) . You can use off the shelf retail chips . Just remember to add 2 mm ( technically 2.4 mm ) worth of nylon washers to each of the eight processor heatsink standoffs . And also add 2 mm worth of thermal gap material on each of the CPU heatsinks . And you need to release both Heatsinks fan data / power connector so they can be independently attached to the Tray's PCB connectors . I use two blacksticks for this operation . Remember to note their original position when installed at the factory . If you reverse the connectors by accident , you'll damage the PCB and the fans will permanently run very fast . And if you really used only 2 mm of washers , just undertighten each heatsink fastener by 1/4 to 1/2 a turn . Oh , use Arctic MX4 paste on everything . That's it !

 

[Macschrauber]

Imho using CPUs with Heatspreader in a Dual 4.1 is a gamble.

On eBay you will find a load of victims that lost the game.

Cutting the glue, heat the solder up a bit and using a vice to pop off the heatspreader is not too difficult.

I use a delidding tool but I do this more than once.