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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


and then I have some Crucial memory labeled


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.

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
Can an RDIMM work in Ubuffered system – A. Moore Nov 1 '15 at 22:39

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