A simple visual method to distinguish ECC from Non-ECC server memory modules.

Tekmart Data Center Team/ October 26, 2021/ Datacenter Infrastructure News, Expert Advise and Opinion, Industry News and Expert Advice, Tekmart Enterprise Hardware Tips, Tekmart Partner Content, Tekmart Support: Storage Systems' Implementation Tutorials

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ECC (and parity) memory modules have a chip count divisible by three or five. … Non-ECC (also called non-parity) modules do not have this error-detecting feature. Any chip count not divisible by three or five indicates a non-parity memory module.

By Tekmart Enterprise Support

By far and large, RAM today comes in the form of DRAM with DDR, DDR2, DDR3, DDR4 interfaces. These standards define the size and pinout connection of the chip, and the electrical interface. They also further define modules known as DIMM – Dual Inline Memory Modules – which line up multiple DRAM chips in parallel so as to present a 64-bit wide memory bus to the memory controller. It could be narrower, it could be wider, it happens it’s defined as 64-bit wide.

That’s for a non-ECC DIMM. An ECC DIMM will have 8 extra bits for every 64 bits, and be 72 bits wide.

A normal memory transaction has 64 data bits traveling between the RAM and the memory controller. If any of those bits are received incorrectly, your computer could crash, causing lost work, or worse, result in silent data corruption that gets rewritten to your disk.

ECC (Error-Correcting Code) adds an additional 8 bits which are generated by the CPU when data is written to RAM, then checked later when the data is read back. The encoding used for these extra bits can identify which bit is wrong if a single bit is flipped, or at least flag the problem if a certain number of multiple bits are bad.

If the data can be corrected, the repaired data is used by the CPU. If it can’t be corrected, the memory controller can ask the memory to send it again, in case it was an error in transmission. If the data is still not usable, the system can report the error.

Its very easy to distinguish whther the modules in question are ECC or Non-Ecc as the Figure 1 below shows.

If you are unsure whether you have ECC or non-parity, count the number of small, black, IC chips mounted on one of your existing sticks of memory. 

• If the number of chips on one side is even, as in 4 or 8, you have non-ECC.
• If the number of chips on one side is NOT even, as in 9, you have ECC.

Figure 1:

It’s that easy ! Visually !