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michaelGR

macrumors newbie
Original poster
Jun 15, 2017
18
4
My Cpu upgrade was very straight forward; EFI firmware upgrade, no problem. I bought a 3x16 Gig Ram kit but the system only recognizes two of the modules (only 32 Gig not 48 gig)

I've tried the usual fixes:
-moved them around and ran them individually
-tried another CPU board
-blew out the ports with compressed air
-did a PRAM and SMC reset

Everything I've read says 48 Gigs shouldn't be a problem.

Thanks for your time,
Mike

Model Name: Mac Pro
Model Identifier: MacPro5,1
Processor Name: 6-Core Intel Xeon
Processor Speed: 3.46 GHz
Number of Processors: 1
Total Number of Cores: 6
L2 Cache (per Core): 256 KB
L3 Cache: 12 MB
Memory: 32 GB
Processor Interconnect Speed: 6.4 GT/s
Boot ROM Version: MP51.007F.B03
SMC Version (system): 1.39f5
SMC Version (processor tray): 1.39f5
Serial Number (system):
Serial Number (processor tray): J50030180BY0A
Hardware UUID: 8FCBB874-26B8-578A-9F91-3318F18C2694
 

h9826790

macrumors P6
Apr 3, 2014
16,615
8,547
Hong Kong
You may have to try reseat the CPU.

Anyway, did you try to put the RAM in a lot 1,3,4 for diagnosis purpose?
 

michaelGR

macrumors newbie
Original poster
Jun 15, 2017
18
4
Can you expand on the diagnosis process? What software do I need, for example?
 

h9826790

macrumors P6
Apr 3, 2014
16,615
8,547
Hong Kong
As expected, slot 3 is the problem.

At this moment, it's hard to tell if it's the slot or the CPU. However, by considering you just did the CPU upgrade. The very 1st thing to try is to reseat the CPU.

If still the same, then reinstall the old CPU back in.

If problem fixed, then you better contact the seller ask for a replacement or refund. It's clearly the CPU's problem.

If old CPU still the same, then pull out the CPU and carefully check the tiny pins inside the socket, if any pin baned, mostly that's the cause.
 

michaelGR

macrumors newbie
Original poster
Jun 15, 2017
18
4
I tested the DDR3 Ram on two identical cpu boards. The results were the same so I think the Ram slots are ok.

I also plugged the 1333 MHz Ram into one of the boards before I upgraded the EFI firmware and all 3 modules registered but just at the lower speed (1066MHz)

Note also that when slots 3 and 4 were populated in the 1,3,4 test that 4 was not recognized either.
 
Last edited:

h9826790

macrumors P6
Apr 3, 2014
16,615
8,547
Hong Kong
If no RAM in slot 3, slot 4 won't work.

You tested the RAM on 2 tray only means the DIMMs are good. I never say they are bad.

The problem is either the slot / socket / CPU.

You tested the tray before upgrade, doesn't mean that you can't damage it during upgrade.
 

flowrider

macrumors 604
Nov 23, 2012
7,246
2,967
I have a dual CPU 5,1. When I upgraded to X5677s, I had the same issue with one of my RAM slots, slot 3. I switched CPUs and the problem followed the CPU. Also there was a red light on RAM slot 3. I exchanged the CPU with the suppler and the problem went away. Obviously a CPU issue.

And has been stated, RAM slot 4 won't work unless slot 3 is populated. However, for the fastest operation, leave slot 4 MT.

Lou
 
Last edited:

Silencio

macrumors 68040
Jul 18, 2002
3,466
1,578
NYC
I recently picked up a CPU tray I had left sitting on the shelf for a while that had a non-functioning memory slot 2. I replaced the CPU with a different one, populated the memory slots again, put it in a Mac Pro, powered it on, et voila — all the memory slots were functional again.

It's a good idea to try reseating your CPU. I haven't re-seating my other CPU or installing it in another tray yet, so I can't say whether my own issue was caused by the CPU being defective / having a bent pin, or just wasn't seated properly in the socket.
 

michaelGR

macrumors newbie
Original poster
Jun 15, 2017
18
4
Ok h9826790, I reseated the CPU and I'm up and running with 48 Gigs of Ram and a 3.46 processor.

I put the old CPU back in to prove the board, the ram and the slots. Everything was fine so it had to be the CPU.

I think the biggest problem with this job is making sure the heat sink mounts squarely on the cpu (like screwing down a head gasket on the old Buick). The heat sink screw should be tightened in an x pattern. When I was getting close to 'contact' I only advanced the screw one turn at a time as I moved through the 'x' pattern. The third time around I was more careful.

Thanks for your time and advice.

All the best,
Mike Reynolds
[doublepost=1497664024][/doublepost]Something else I noted that may or may not be an issue. There was a slight discoloring on a few of the contacts on the underside of the CPU. 3 or 4 pins in diameter. I cleaned it off with some Isopropyl on a Q-tip. This removed it.
 
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