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Xeons just let you use ECC RAM if you want to, there is no actual requirement.

not all non-ECC RAM is compatible. I've tried Mushkin Silverline, which didn't work, and now I use Crucial.
 
Non-ECC RAM will work fine as long as all modules are non-ECC. You cannot mix ECC and non-ECC RAM

That would explain the RAM check fails then. 😀

Has anyone compared the speed difference between ECC and Non ECC RAM in their Mac Pro? I assume Non ECC should be quicker.
 
That would explain the RAM check fails then. 😀

Has anyone compared the speed difference between ECC and Non ECC RAM in their Mac Pro? I assume Non ECC should be quicker.

3x2GB unbuffered ECC is around 2% slower than 3x2GB unbuffered non-ECC.

While there are optimum configurations for memory on the Mac Pro, really the best course of action is get as much capacity as you can utilize properly for a budget you feel comfortable with. The speed differences aren't worth worrying about.
 
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