Did you ever get this resolved?  I need to do the same thing.  I actually BOUGHT Non-ECC ram and replaced the ECC ram in my workstation but it wouldn't boot.  Did you find that ECC is in fact required?

Judging from the fact that Crucial and Dell both only list ECC memory in their 'compatible with the 670'-list, I'd say you're pretty much stuck with having to buy relatively expensive ECC memory. Also the fact that chipsets that support dual processors are commonly used in high end workstations or mid range servers, ECC memory isn't unusual to see as a requirement of those chipsets.

Hello dears,

Well i have Precision Workstation 380, I bought it in 2005 and i love this macine very much! It has 2 Sticks of 512MB DDR2 (ECC). Now one 512MB Stick having issues and i want to replace it. I have 2 questions in this regard.

1st Question: May I replace both 512MB ECC sticks with 1 OR 2 GB Non-ECC Memory? Will it work well with Dell Precision 380 Workstation?

2nd question: If I can't replace ECC with Non-ECC, I would like to buy 1GB ECC Memory, will it work with my remaining 512MB Stick? That would be 1.5GB of ECC Memory. (1 stick of 512 and 1 stick of 1GB).

I now dont live in USA, so i need to get the memory from some of my friends in USA, that will take time. so the prompt reply will be highly appreciated.

Thanks

I realize this is an old post, but since i googled and this is where i ended up i thought i would contribute for informations sake.

the Precision 380/390/t3400 WILL work with ECC or non-ECC, but you cannot mix them. i have in front of me right now a 390 booted with 2x non-ecc A-data sticks with no problem. I also have 2x unbuffered ecc sticks that came with the system that also work. I cannot mix the memory or i receive an error at boot.