cMP 5,1 - Stuck at Apple Logo after 8x8GB RAM Upgrade

[n8ballz]

I just upgraded the RAM in my cMP to 8GB DIMMs. They are all 8GB 1333 DDR3 Registered DIMMs.

• I am able to see the Apple logo and an empty progress bar.
• I am able to boot to USB or CDROM. I ran a full 4-cycle memtest on all 64GB on the MacPro (Test PASSED)
• I did PRAM and SMC reset and tried reseating the RAM.
• It works with 6x8GB DIMMs

Any other suggestions?

 

[Darmok N Jalad]

When you say 6x8GB, you're booting with not all the RAM installed? Maybe one stick is the problem.

 

[n8ballz]

When you say 6x8GB, you're booting with not all the RAM installed? Maybe one stick is the problem.

I ruled out that case by putting those DIMMs into slots 1&2 and removed the other 8GB DIMMs that were working as well.

 

[h9826790]

Which OS？

 

[Darmok N Jalad]

I ruled out that case by putting those DIMMs into slots 1&2 and removed the other 8GB DIMMs that were working as well.

What model of cMP is it? CPUs?

 

[vetruvian]

I ruled out that case by putting those DIMMs into slots 1&2 and removed the other 8GB DIMMs that were working as well.

Any chance there is a problem with one of the slots, not the sticks?

 

[devon807]

I also believe that it may be a DIMM slot. Try blowing out the slots with compressed air. Sometimes dust can get shoved in to the slots when freed.

 

[ActionableMango]

What is the brand and model number of the RAM?

 

[barmann]

I once had to reseat RAM modules several times before all of them were recognized .
Had no startup issues though, that might point to a motherboard connection problem .

Either way, my rule with Macs is try again , and again, and again .
It's a stupid rule, but works for me .