R420 Advanced ECC disabled for memory sockets a1,a4,b1,b4

Okay. Thanks.

If I am using optimer mode, which option will get better performance?

Option 1

A2,A3,A5,A6

B2,B3,B5,B6

Option 2

A1,A2,A3,A4

B1,B2,B3,B4

I've always been under the impression that it's because there are only 3 channels allocated to each proc.  Advanced ECC mode must reserve the channel that those slots are on, which makes them unavailable for use.  The rest of the memory slots are on the other 2 channels left.

Thanks for the good info.

I dont have many R420s but lots of R620s so I wasnt familar with the disabling of slots for advanced ecc.

I use optimer mode in all systems. To verify the banks are even and setup optimally in the R620s,  I make sure advanced ecc is an option and not read only (using syscfg.exe). This logic doesnt work for the R420s.

If you are using quad-rank DIMM's, best performance would be 1,2,3 (all white slots), but if you must use all four per processor or you are using dual-rank DIMM's, then do 1,2,3,4 (manual indicates to populate white slots first, meaning, you populate in numerical order).

I've always been under the impression that it's because there are only 3 channels allocated to each proc.  Advanced ECC mode must reserve the channel that those slots are on, which makes them unavailable for use.  The rest of the memory slots are on the other 2 channels left.

It disables the slots so that it can increase the bus width. X4 memory is capable of advanced error correction without using advanced ECC mode. Advanced ECC mode allows X8 memory to have the same error correction features, so if you have X4 Dimms you should not use advanced ECC mode.

If I am using optimer mode, which option will get better performance? Option 1 A2,A3,A5,A6 B2,B3,B5,B6

This is not a valid configuration for optimizer mode. You need to start population with slot 1 when optimizer mode is enabled. This would be the best way to populate:

1,2,4,5 with both processors.

A1 A2 A3 are one bank. A4 A5 A6 are the 2nd bank. Our 12th generation servers allow for flexible memory configurations, so you can have uneven bank populations. For best performance you want to populate the banks evenly.

In the manual on page 46 and 47 it shows the recommended memory population.

ftp://ftp.dell.com/Manuals/all-products/esuprt_ser_stor_net/esuprt_poweredge/poweredge-r420_Owner%27s%20Manual_en-us.pdf