MP 1,1-5,1 Why Is RAM Dying Then Coming Back to Life?

[danallen]

Just last night, two were out. Now 3 are out.

Questions:
1. Can the replacements be any 1333 MHz DDR3 ECC 8GB sticks?
2. What causes memory to die like this?



UPDATE: Since first posting, I have done two restarts, moving the sticks around to reseat them each time. Different numbers of sticks come online each time. Why the variation. All these screen shots were made in the last hour.

How did some sticks come back to life?

 

[danallen]

Deleted, content merged into OP

 

[ZombiePhysicist]

That’s weird. My guess is one of the sticks is dying. Have you tried removing the 4 sticks and maybe cleaning the contacts/connections and re-seating them?

Also running the apple/memory diagnostics.

 

[ReanimationLP]

I recommend as well checking the northbridge heatsink and making sure the plastic pogo pins haven't let go.

 

[mattspace]

I had a recalcitrant RAM stick settle down after performing an RTC reset. Might be worth a try.

 

[Matty_TypeR]

Some times its just a poor connection, I use a soft tooth brush with IPA to clean ram slots, let it dry out. Then the same with a soft cloth with IPA clean the ram where it slots in. Oxidation of the pins with dust and dirt can cause bad contact.

After cleaning do the above mentioned RTC reset. remove power lead from back of mac, wait a min and re connect. if the ram sticks are ok they should now work, if not then bad ram. also make sure when you re seat the ram its even push down both side's at same time or the stick of ram can go in wonky.

 

[danallen]

Have not opened the computer since last posting. Back to full memory.

Gotta be a problem with the contacts. The plastic heat sink screws have were replaced with metal before I got this computer. I tend to assume that means they won't pop the way the plastic ones can.

 

[ToniCH]

I see you have upgraded CPU's. According to various posts on the forum: if the processor cooling towers are too tight or unevenly tightened it can cause memory problems just like yours. I guess the CPU-tray bends when the towers are tightened too much.

However, I do not know if this applies to your 5.1 too or if it applies only to those machines with 4.1 CPU-trays though. More wiser ones will comment on this, I am sure.

 

[Macschrauber]

The memory controller is inside the cpu. If not all contacts make good contact this could be a reason.

Another reason could be oxidation of the ram sticks / ram slots.

Plug the machine off and carefully reseat the ram sticks 5 times.

one could also clean the contacts of the sticks with isopropyl. Avoid aggressive sprays.

 

[danallen]

I see you have upgraded CPU's. According to various posts on the forum: if the processor cooling towers are too tight or unevenly tightened it can cause memory problems just like yours. I guess the CPU-tray bends when the towers are tightened too much.

However, I do not know if this applies to your 5.1 too or if it applies only to those machines with 4.1 CPU-trays though. More wiser ones will comment on this, I am sure.

The CPUs were in the computer when I bought it in 2014