I'm upping the RAM in one of our servers from 2GB to 4GB. Looking around in the BIOS, I see the following settings:

DRAM ECC Enable (Enabled)
MCA DRAM ECC Logging (Disabled)
ECC Chip Kill (Disable)
DRAM Scrub Redirect (Disable)
DRAM BG Scrub (Disabled)
L2 Cache BG Scrub (Disabled)
Data Cache BG Scrub (Disabled)
IOMMU Mode (Disabled)

Should these be turned on? And for the background scrubbing options, various times are in nano and microseconds; how would one go about calculating the optimal time to use?

Additionally, IOMMU has an options for Best Fit and Absolute, and then allows me to set the aperture size in MB. What should this be set to? We're running VMWare Server on this box, so my basic understanding is that IOMMU is helpful, but don't know what the ideal aperture would be.

2 Answers 2


Sounds like the server your using is AMD based; here is some information on i/o virtualization and AMD's IOMMU option that might help. -> http://developer.amd.com/documentation/articles/pages/892006101.aspx -> Specifically under "What's an IOMMU."

Some more info related to chipkill and scrub modes in bios related to ECC with detailed information on ECC Scrubbing and performance when using some of these options -> http://episteme.arstechnica.com/eve/forums/a/tpc/f/77909774/m/346009152831

  • 1
    The AMD link is broken, can you please summarize per normal Stack Exchange guidelines? Feb 13, 2016 at 7:54

For everything before the IOMMU option, a look at http://forums.aida64.com/topic/1102-is-my-ram-running-in-ecc-mode/ and the links therein could gain some insight.

Coarsely spoken: enabling all the ECC stuff enhances your data integrity for the price of a bit of performance.

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