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I've got an SE7501HG2 board in a server that currently has (unknown make) 4x1GB DDR266 ECC Registered DIMMs installed. The board has three banks, so I'd like to install another 2x2GB.

The following statement appears in the technical specs document for the board:

Note: Intel does not test, recommend, or support mixing of memory types within the same server system. Functionality issues may occur if mixed memory types are installed in the same server system. Intel recommends that memory modules of identical size, type, banking and stacking technology, and vendor are installed in each server system. Intel will not provide support for issues encountered when mixed memory configurations are in use.

Now my gut tells me that this is just one of "those things" they always say to minimize the chance of strange little glitches. The memory I'll add will be from Crucial or some other well-known vendor and be specifically compatible with the board. If this registered stuff was cheaper I'd just replace the existing DIMMs, but at $150+ for 2GB I'd rather just add more.

I'm just reaching out to you guys in case somebody has actually had a problem doing this. Thanks.

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Generally speaking you can pretty much mix and match memory speeds these days and the memory controller will cope, running all at the speed of the slowest. But no manufacturer is going to support this as there are effectively an infinite number of combinations and you can bet that some of them would introduce instability through odd timing issues.

You are much less likely, I think, to get away with mixing registered RAM with unregistered or EEC with non-EEC on the same board though.

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Yeah that's pretty much been my experience as well. The memory I'll be adding will be of the same type, just a different size and manufacturer. I just wanted to make sure there weren't any gotchas with these fancy pants server boards. – Boden Oct 2 '09 at 16:07

I've had nothing but hassles with mixed memory chips, everything from just not acknowledging the additional memory through to full on failure to boot, whilst using the memory separately is fine. Biggest problems came when dealing with HP servers when even the slightest difference caused problems (not sure if it's changed but HP's memory model numbers differentiated Mhz size and form, not cas,ras etc.)

The main thing to be conscious of is which memory channels are paired together, and make sure each pairing is the same brand/speed and for the most part you should be good.

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As long as you use the same memory types it should be okay. After all, multiple memory module vendors (think Corsair, Kingston) use memory chips from the same few chip manufacturers (think Infineon, Hynix). Unless you buy the modules at the same time, you may even end up with different memory chips. However, if you do end up mixing chips of different performance, thay may screw things up a bit.

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