[Wowfunhappy]

When I last looked at this (a couple of years ago), it wasn't just the cost difference—the ECC memory available to purchase was also slower than non-ECC offerings, or at least cost significantly more if I actually wanted the same speed. At least for me, going ECC simply didn't make sense.

Caveat that I was building a gaming PC at that time, I might have gone differently for a home server. And, this was before the memory market went nuts for unrelated reasons.

[adrian_b]

Yes, ECC DIMMs are available only for the memory speeds guaranteed to work by the manufacturers of CPUs, like Intel and AMD, e.g. for up to DDR5-5600 in UDIMMs or DDR5-6400 in RDIMMs.

The "gaming" DIMMs are available in much greater speeds, which are "overclocked" speeds, i.e. there exists absolutely no guarantee from Intel or AMD that they work at the advertised speed, even if they frequently do work.

However, with such overclocked DIMMs, you do not know how well they work. They might work most of the time, but e.g. in a hotter room they might have an error or two per day without you noticing, especially if the computer is used mainly for games.

For someone doing anything professional on a computer, overclocked DIMMs are not an acceptable choice.

[jmb99]

> ECC DIMMs are available only for the memory speeds guaranteed to work by the manufacturers of CPUs, like Intel and AMD, e.g. for up to DDR5-5600 in UDIMMs or DDR5-6400 in RDIMMs.

This is not true[1]. These DIMMs are not guaranteed to work with all Threadripper CPUs, but they are guaranteed themselves to be stable at their advertised frequencies, which are higher than JEDEC. (And from my experience, 9000-series threadripper is perfectly happy to drive 8-channel 1Rx8 at 7200MT/s.)

AMD (and possibly Intel, I don’t have any experience with their recent offerings) also lets you overclock memory completely on WRX90. So if you buy JEDEC sticks, you’re welcome to try to push them as hard as you can.

[1] https://v-color.net/products/ddr5-ocrdimm-amd-wrx90-workstat...

[zargon]

AMD, Intel, and motherboard manufacturers do qualify the CPUs and motherboards for "overclocked" (above JEDEC) memory speeds. The systems are designed to work at the overclocked transmission speeds. They need to be paired with memory modules that are capable of functioning at those speeds. With ECC presently being a datacenter thing, companies only make it according to JEDEC specs. If ECC were standard for everyone, then the pre-qualified overclocked "gaming" memory modules would be available in ECC configuration as well.

Without ECC, nobody knows if their memory is working or not. Regardless whether it is running a standard JEDEC speed or an overclocked one.

[adrian_b]

The motherboard manufacturers test their motherboards, to ensure that they typically work with overclocked memory modules.

If you buy a complete gaming computer which includes overclocked memory, then hopefully the vendor has done a burn-in and has tested for some time the computer, as sold.

However, if you buy the CPU yourself, neither Intel nor AMD provides any guarantee that the CPU will work with overclocked memory.

It is upon you to test your assembled computer, but true tests would require a very long time and a climatic chamber, to offer any kind of certainty that the combination CPU-DIMMs works at the desired speed.

If you have ECC memory, you can try to overclock it and at least in this case you will know for sure if the memory works at the higher speed, or not.

Overclocking ECC memory is actually a method frequently used to verify whether the hardware ECC support and also the operating system EDAC driver work OK.

[willis936]

The ECC on the GTX 1080 let me figure out the optimal overclock with the only feedback mechanism being benchmarked throughout.

[zargon]

> However, if you buy the CPU yourself, neither Intel nor AMD provides any guarantee that the CPU will work with overclocked memory.

There's no guarantee that it works with standard clocked memory either.

[adrian_b]

Both AMD and Intel publish on their site, for each CPU model, the maximum supported memory speed.

If the CPU does not work at that speed, you are entitled to a replacement or a refund.

For instance, AMD Ryzen™ 9 9950X3D is guaranteed to work with DDR5-5600, but with nothing faster. No AMD non-server CPU goes above this limit for DDR5.

Some of the Intel CPUs are guaranteed to work with faster memories, e.g. Core Ultra 9 285K with up to DDR5-6400, and the very recently launched Core Ultra 7 270K PLUS with up to DDR5-7200.

[undersuit]

So as I was overclocking my AMD Ryzen 7 2700 I discovered that the Infinity Fabric has ECC because if I tried to run my fancy DDR-3466 ram at full speed I started getting logged errors from it. Those failed transactions slow down the system because the data needs to be corrected or even re-sent. The RAM runs fine overclocked at DDR4-4200 in a newer system, but my old Ryzen 7 2700 couldn't handle anything past DDR4-3266 without the errors creeping in.

Without the reported ECC on Infinity Fabric I would have had no idea that the errors were happening and affecting performance.

[jmb99]

There are absolutely fast DDR5 ECC DIMMs[1]. Just break out your wallet (and piggy bank, and rainy day fund, and..)

The main reason there aren’t more options here is that a) high-frequency memory usually isn’t sufficiently stable, unless binned, and b) there’s very, very, very little demand.

[1] https://v-color.net/products/ddr5-ocrdimm-amd-wrx90-workstat...

[Wowfunhappy]

Right, my point was that it's no longer 3% of the system cost.

[pseudalopex]

Intel and AMD segmented the market. Workstations and servers use registered memory. Desktops use unregistered memory. Most desktop motherboards or CPUs do not support ECC. And most people who want ECC want reliable more than fast. So ECC unregistered above standard speed memory is made and priced for a niche. But this would change if ECC was standard.

[justsomehnguy]

The same reason your utility trucks isn't rated for 200KM/H speeds.