failing mac pro apple memory

[ihabia]

Have someone had problems with ECC 667Mhz apple memory on Mac Pro?
I had bought mine with four modules of 512MB and after an year and a half two modules were no more recognized. Looking inside my mac I saw a red light on my DIMM Riser A clearly indicating that a memory bank was broken, I suppose that just one of them is broken because I know that this memory works only in dual-channel.
After this problem I bought four banks of IBM Chipkill memory for a total of 8GB of ram and I place them in DIMM riser A DIMM 1-2 and DIMM riser B DIMM 1-2 with my my old two 512MB working Apple memory banks in DIMM riser A DIMM 3-4.
Is this a good configuration?

I ask this because after the last 10.5.3 update at reboot my system profiler showed two 1GB modules in DIMM riser A DIMM 1-2 instead of two 2 GB modules. After a shout-down this issue disappeared.
Any suggestion or similar problems out there?

 

[yeroen]

IBM chipkill?

It sounds like you bought FB-DIMMS designed for rack servers. If they don't have the big heatsinks on them, then you're going to have trouble.

 

[ihabia]

IBM chipkill?

It sounds like you bought FB-DIMMS designed for rack servers. If they don't have the big heatsinks on them, then you're going to have trouble.

Yes, I don't have the big heatsinks but I hadn't been luckier with apple memory which does have. I know that chipkill could run hotter and so maybe I will get more fans noise... This is not a problem.
I hope that my IBM memory will last more than one year and a half and I'm wondering if hotter means shorter life. I could also take off the apple heatsinks and put them on my IBM memory but I don't know if it's worth.
Someone already experienced?

 

[nanofrog]

...I'm wondering if hotter means shorter life. I could also take off the apple heatsinks and put them on my IBM memory but I don't know if it's worth.
Someone already experienced?

In short, Yes. Chips have thermal specifications that must be satisfied, or "death" will occur. It is recommended that you do use larger heat sinks if the units supplied are too small.

1. Clean both the heat sink mounting surface and chip surface with alcohol first.
2. Use thermal paste between the heat sink and chip surface. (Thin coat on aluminum surface will do).
3. Apply heat sink & mounting hardware.

The other solution would be to increase fan speed. It may be too loud to tolerate though. Best to go ahead and change to larger heat sinks anyway.

 

[yeroen]

The most sensible solution is to purchase some good, inexpensive, 3rd party memory that's designed for the Mac Pro's stringent thermal requirements. OWC is perhaps the most popular brand around here, and rightly so. It's only a small fraction of the cost of Apple's exorbitantly priced memory and is every bit as robust.

 

[ihabia]

Thanks for the suggestions.