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I have an old Mac Pro I decided to upgrade. I found a company on eBay selling "16GB 4X4GB DDR2 MEMORY RAM PC2-5300F 667MHz ECC FB-DIMM" for a good price so I bought two units (32GB total). (Kingston PN# F51272F51)

I installed the memory and all 32GB of the RAM is showing in System Report, but it does not show as ECC.

Here's about the Mac itself:

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Here's the memory section:

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According to Wikipedia, most Registered ("Buffered") RAM is also ECC, but Buffered RAM can also be non-ECC RAM.

Is the RAM I purchased ECC?

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    What's the make and model of the RAM? – Allan May 10 '18 at 14:56
  • Kingston F51272F51. – Swisher Sweet May 10 '18 at 15:07
  • My Mac Mini has the legend ECC Disabled when the Memory Slots section is selected. Individual RAM slots do not indicate ECC. In your second screen-shot, you've selected the first RAM riser. Select Memory Slots (above) and see what is reported. – IconDaemon May 10 '18 at 15:10
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It's not showing as ECC because it's not ECC.

According to Wikipedia, most Registered ("Buffered") RAM is also ECC, it isn't always the case.

That's not exactly correct. Registered memory has ECC functionality, but not all ECC is registered. Kingston goes on to explain the difference in the FAQ: What is the difference between registered, unbuffered, ECC and fully buffered memory?

Secondly, the memory you specified, the Kingston F51272F51 is not listed anywhere as being ECC. It is listed as being Fully Buffered, however.

Finally, looking at the "supported systems" for this memory on Kingston's website, Apple is nowhere to be found. So, while is technically works, it's not "correct."

enter image description here

Unfortunately, what you purchased on eBay was not accurately described. The actual memory that you need from Kingston is KTD-WS667

  • No, the OP is correct. Buffered/registered means there's a chip(s) in the data or command path that regenerates the signal between the DRAM and the motherboard. ECC means the memory returns 72 bits per address instead of 64 bits. Those are independent functions. (The confusing wording that Kingston uses is a quirk specific to FB-DIMMs; the AMB serializes all data, so the bus always has the capability to handle ECC bits. Registered RAM doesn't care about ECC, Buffered RAM just requires one extra buffer chip for the added width) – user71659 May 15 '18 at 5:13
  • @user71659 - I don't think you read/understood the FAQ I linked clearly. You just repeated what it said. – Allan May 15 '18 at 12:07
  • No, I understand completely. Only FB-DIMMs always have the "functionality" of ECC, because of their unique architecture. FB-DIMMs are completely different from any other memory bus. Any other non-ECC platform is missing the bus wires (DIMM pin count) and controller hardware for ECC, regardless of registration or buffering. Kingston is nitpicking one specific obsolete memory architecture by mentioning an ill-defined "functionality". The Wikipedia quote is 100% correct. – user71659 May 15 '18 at 15:50

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