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I am using a HP DL 160 G6 server that according to specs takes PC3 Registered or Unbuffered. When I combine the two types of memory below the system will not POST. When I use just the first type of memory listed the system will POST.

I have two pieces of HP memory that came with the server labeled

PC3-10600E-9-10-E0

and then I have some Crucial memory labeled

PC3-10600R-9-10-B0

I wager that the R means Registered memory and the E means ECC - then shouldn't the crucial memory boot with the system according to the HP specs? Or does the E mean it is Unbuffered and therefore I shouldn't mix and match as according to this HP memory config doc?

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up vote 2 down vote accepted

The difference between the RAM modules you have is UDIMM (unbuffered) versus RDIMM memory; unregistered versus registered. They cannot be mixed in the same server. So you are correct, the memory guide states not to mix the two. http://h18000.www1.hp.com/products/quickspecs/13344_na/13344_na.HTML#Memory

Do not mix Unbuffered memory (UDIMMs) with Registered memory (RDIMMs).

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That is what I was beginning to suspect. My next question is that since the Crucial memory is labeled E for ECC does it stand to reason that ECC and Non-ECC fall into the Unbuffered category? –  Jeremy Hajek Jan 13 '11 at 21:05
    
UDIMMs can be ECC. There are just greater restrictions on them with Nehalem-based systems. I have plenty of servers using the UDIMMs that come standard on the HP 100-series servers. You're just limited to population of 2 slots per DIMM bank and a total of 12GB ram on the server you're dealing with. –  ewwhite Jan 13 '11 at 21:09
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