UDIMM and RDIMM use the same DRAM chips. And my understanding is that the fabs can switch between DDR5, LPDDR5, and maybe HBM as needed. This means high demand for one type can create a shortage of the others.

> This means high demand for one type can create a shortage of the others.

Wouldn't that mean that a shortage of DRAM chips should cause price difference in all of them? Not sure that'd explain why RDIMM prices aren't raising as sharply as UDIMM. That the fab and assembly lines have transitioned into making other stuff makes sense why'd there be a difference though, as bradfa mentioned in their reply.

It's a valid question if you're not familiar with the RAM market. Sorry you're getting downvoted for it.

The manufacturers make the individual chips, not the modules (DIMMs). (EDIT: Some companies that make chips may also have business units that sell DIMMS, to be pedantic.)

The R in RDIMM means register, aka buffer. It's a separate chip that buffers the signals between the memory chips and the controller.

Even ECC modules use regular memory chips, but with extra chips added for the ECC capacity.

It can be confusing. The key thing to remember is that the price is driven by the price of the chips. The companies that make DIMMs are buying chips in bulk and integrating them on to PCBs.

> Even ECC modules use regular memory chips, but with extra chips added for the ECC capacity.

Quite a few unbuffered designs in the past had a "missing chip". If you ever wondered why a chip was missing on your stick, it's missing ECC. Don't know if it's still the case with DDR5 though.

I have not seen that yet DDR5, I think the signal integrity requirements are too high now to even have unused pads open. Most sticks don’t appear to have many traces at all on the top/bottom sides, just big power/ground planes.

Also with DDR5 each stick is actually 2 channels so you get 2 extra dies.

There's some new half assed ECC type of RAM, not sure the name.

Was reading a series of displeased posts about it. Can't seem to find it now.

On die ECC for DDR5. Which corrects locally but does not signal the host or deal with data between the die and the CPU.

Presumably this is being marketed indistinguishably from regular ECC RAM?

If so, that's terrible news. It was already difficult enough to find ECC RAM for "workstation" class machines (i.e.: High end, non-server CPUs that support ECC such as AMD Threadripper).

It's not - ECC RAM still means real, between the RAM and CPU ECC. It's literally an extra 8 bits per channels, for an extra 16 bits per dim. 40 bits vs 32.

Thanks, drove me bananas trying to find that again.

There's 9 bits in an ECC byte.

Because manufacturers transitioned fab and assembly lines from low margin dram to higher margin products like hbm, hence reducing dram supply. But the demand for consumer grade dram hasn’t changed much so prices for it go up.

The chips come from same factory. And difference betweeen those two is... a buffer chip. And extra ram die for ECC

wait, are you saying that there's no difference between regular and premium gas?

The “regular” and “premium” label at the pump is misleading. The premium gas isn’t better. It’s just different. Unless your car specifically requires higher octane fuel, there is no benefit to paying for it. https://www.kbb.com/car-advice/gasoline-guide/

You get slightly better mpg on premium, just not enough to justify the cost.

Not unless you’re adjusting timing. Premium gas has lower energy per unit mass and per unit volume than standard gas.

> Not unless you’re adjusting timing.

Which, every modern ECU will do automatically based on output from the knock sensors.

Only if it has the physical ability to use more octane.

In theory, your average Camry running on 87 is pulling spark timing to ride the edge of knock for best fuel efficiency by being lean, but how much? It was designed to be safe on even kinda shitty gas, that has lower than 87 octane at points, and the ECU is going to err on the side of caution.

That naturally aspirated 2AR-FE in a Camry does not have the ability to compress harder, so if you put 93 in it, it may only be able to "utilize" the extra knock resistance up to say 89 by advancing spark timing.

Meanwhile your average Golf TSI probably can, and the VW GTI I have demonstrably gets better gas mileage on 93 octane, even though it is "rated" for 87 octane (and therefore has a lower mpg claim than it is capable of), but this was an engine that previously was rated at 91 octane and nerfs itself so hard on 87 that it is dramatically easier to stall, and the power figures are rated on 91 octane anyway.

You are almost certainly spending more money on gas even if you eke out a percentage point or two extra mpg on higher octane fuels, as they are priced at higher margins and have lower scale.

This may surprise you, but gas stations typically only have two grades of fuel stored in tanks. Mid-grade gas is mixed at the pump from the other two.

no, but made in same place with mostly same ingredients, just different ratio to hit higher octane (and in some cases some extra additives).

Also vary a bit between winter a summer, basically in winter they can get away with putting a bit more volatile compounds coz it's colder