alt Hacker NewsRight. Everyone agrees that real ECC is more robust, and production servers of course run it. But it seems to me that if most RAM bitflips are in the module itself (rather than in transmission to CPU), then on-die ECC could in theory make the probability of a bitflip in practice so low that for things like home servers it isn’t worth the price premium for real ECC. But without data on this, everyone is just speculating.
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No.
On-die ECC was added in DDR5 because the error frequency has increased too much.
Its only effect was that now DDR5, as seen externally, has a reliability similar to that of the older memory generations. On-die ECChas not brought any serious improvement in reliability. It has just prevented the degradation of the reliability.
The errors generated internally are caused mostly by the ionizing radiation from the environment, which discharges the storage capacitors.
However there are many errors that appear during the communication between memories and the CPU, which are caused by the electrical noise from the environment.
These external errors are much less likely to appear for soldered DRAM. Because of this, for soldered LPDDRx memory it is less important to have end-to-end ECC than for socketed modules, which are much more vulnerable to noise.
The DDR5 standard has some options for using some error detection for the communication link, but it is impossible to know whether a given computer or motherboard has implemented such options or if they are enabled by the firmware when the motherboard has the physical support.
The only way to be certain that the memory works fine is to use ECC that covers completely the circuit from the CPU memory controller to the values stored in the DRAM and back to the CPU memory controller and your operating system has the appropriate device driver for obtaining the error reports.
This is the attitude that needs to change. If RAM is 25% of the system cost (say for a home server in your example), then the cost for ECC is 3% of the system cost. There is no world where accepting data corruption in order to save 3% cost is a reasonable tradeoff. ECC should be standard, period.