Member Avatar for ashikkalam123

I have heard of 72 bit and 64 but memory but haven't understood what the big difference is.

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Short version: the “72‑bit” label refers to the physical width of a DIMM (64 data bits plus 8 extra bits), not to a 72‑bit CPU. The extra eight bits store check/correction information so the memory subsystem can detect—and in common implementations correct—bit errors that would otherwise corrupt data. This is why server and workstation modules are often wider than desktop modules.

A little more detail: modern ECC for 64‑bit words uses a Hamming‑style scheme plus an overall parity bit (commonly called SECDED: single‑error‑correct, double‑error‑detect). That combination requires 8 check bits for each 64 data bits, which is why modules and the memory bus appear as 72 bits wide. Parity memory (detection only) historically used a similar extra‑bit layout but cannot correct errors. @tech‑master was on the right track; and were right to be puzzled—“72‑bit” shows up rarely outside server contexts and can be confused with CPU bitness.

How to tell in practice and what to watch for:

  • Physically, ECC DIMMs commonly have an extra chip per rank (with x8 chips you often see 9 per rank).

  • Not all motherboards/CPUs support ECC; some support ECC only in registered/buffered DIMMs (RDIMM/LRDIMM). Mixing ECC and non‑ECC typically disables ECC.

  • Quick checks:

    sudo dmidecode -t memory   # Linux: look for "Error Correction Type"
    wmic memorychip get DataWidth,TotalWidth,DeviceLocator   # Windows: TotalWidth = 72 indicates ECC

Operational notes: a few corrected errors logged occasionally are normal; growing counts of corrected errors or any uncorrectable errors indicate failing memory or other hardware issues and merit replacement and testing. If this was the quiz question, the concise answer is: a 72‑bit memory module carries the extra 8 bits used for parity/ECC in addition to the 64 data bits.

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Member Avatar for coolraj003

Are you sure you heard about 72 bit not 32 bit memory as i never heard anything on 72 bit memory?

Raj

Member Avatar for ashikkalam123

yeah its 72 bit I am talking about,I hadn't heard about it till I came across it in an IT Quiz in TV.I couldn't get hold of the answer but the question certainly was "what is the difference between 72 bit and 64 but memory?".

Member Avatar for coolraj003

Most generic answer wud be in the question itself...the 72 bit memory is a "72 Bit memory" and 64 bit is....you guessed it "64 bit memory"...bravo!!!;)

But i d say it might be some new development which might be able to handle 72 bit programming. Never heard of it. Do share with us if you find more information on this.

Regards
Raj

Member Avatar for ashikkalam123

One of my friends is of the opinion that in 72 bit memory there is an extra 8 bits which is set aside for some particular purpose,not sure of what it is though.

Member Avatar for tech-master

72bit memory is ECC memory the ECC is for error correcting.

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