Question How does the CPU know which RAM is installed ?

[miha2]

The real question is... not quite that, although heavily related.

(This is only out of curiosity and I'm not saying that anyone should even attempt to do this.)

Let's imagine a (hypothetical) situation where someone (for simplicity, I, but it doesn't matter who, and in reality, it's much simpler for some robot hand to do it all, so... let's change that to someone's robot hand) takes, say, DDR3 and DDR5 sticks. Same capacity, same voltage. And... Unsolders capacitors, chips, voltage regulators, and everything else. On both. And puts DDR3 stuff onto DDR5, and DDR5 stuff onto DDR3. Will the (say, 14900K or whichever) CPU recognize that the "new" DDR5 is in fact DDR3? Will, say, 4770K recognize the "new" DDR3 as... not DDR3? Would both power on? Would either work?

I understand that the two may have completely different parts and everything. But would it still be possible under certain circumstances? If so, under which?

 

[Lutfij]

You're forgetting that controllers are involved in all of this. Said controller won't speak to IC's just like that unless they're programmed to. First controller would be on the processor since the memory controller was moved from the North Bridge to the CPU's die hence why it's now known as the IMC or integrated memory controller. The other aspect would be practicality/feasibility. You're wasting an awful amount of resources to transplant IC's onto a platform that doesn't support it.

Will the (say, 14900K or whichever) CPU recognize that the "new" DDR5 is in fact DDR3?
No

Will, say, 4770K recognize the "new" DDR3 as... not DDR3?
No

Would both power on?
No

Would either work?
No

If it were possible, you'd see a post on the www and everyone would be writing articles around it.

Moved thread from Components section to Memory section.

 

[_D_D]

BIOS reads SPD data.

IIRC Core2 could support DDR2 or DDR3 and X99 boards could come with DDR3 or DDR4 with different types to boot but the board itself would support one or the other.

 

[SkyNetRising]

Will the (say, 14900K or whichever) CPU recognize that the "new" DDR5 is in fact DDR3?
Will, say, 4770K recognize the "new" DDR3 as... not DDR3?
Would both power on?
Would either work?
But would it still be possible under certain circumstances? If so, under which?

No, No, No, No and No.
DDR3 and DDR5 chips have completely different pinouts. They use different voltages.
Attempting something like that would most likely cause irreparable damage to cpu.

 

[USAFRet]

The real question is... not quite that, although heavily related.

(This is only out of curiosity and I'm not saying that anyone should even attempt to do this.)

Let's imagine a (hypothetical) situation where someone (for simplicity, I, but it doesn't matter who, and in reality, it's much simpler for some robot hand to do it all, so... let's change that to someone's robot hand) takes, say, DDR3 and DDR5 sticks. Same capacity, same voltage. And... Unsolders capacitors, chips, voltage regulators, and everything else. On both. And puts DDR3 stuff onto DDR5, and DDR5 stuff onto DDR3. Will the (say, 14900K or whichever) CPU recognize that the "new" DDR5 is in fact DDR3? Will, say, 4770K recognize the "new" DDR3 as... not DDR3? Would both power on? Would either work?

I understand that the two may have completely different parts and everything. But would it still be possible under certain circumstances? If so, under which?

I smell smoke...

 

[miha2]

(I'll just comment on quotes from everyone here in one reply)

You're forgetting that controllers are involved in all of this. Said controller won't speak to IC's just like that unless they're programmed to.

So... Is it possible to reprogram it to "accept" the "new" RAM?!

The other aspect would be practicality/feasibility.

(This is only out of curiosity...)

DDR3 and DDR5 chips have completely different pinouts. They use different voltages.

I understand about different pinouts, so if you were to (re-)read my post more carefully, you'd see that what I'm saying is that if you were to unsolder everything from DDR3 and DDR5 and swap components from one stick to another, would that in some way make it work on the respective CPU? That is, say, DDR3 on i7 14700K and DDR5 on i7 4770K

About voltage - there are quite a few 1.35, 1.5, and other voltages on both DDR3 and DDR5. Since there may be a lot of technicalities over "how" RAM gets it, that may be another factor. But either way, is it possible to make voltage regulator work like the same way as the one on the other RAM?

BIOS reads SPD data.

OK... still, would the computer start with the swapped components on the RAM sticks?

IIRC Core2 could support DDR2 or DDR3 and X99 boards could come with DDR3 or DDR4 with different types to boot but the board itself would support one or the other.

I think there was the same situation with 10-series CPUs or something like this, where a CPU had IMC for both DDR4 and DDR5, allowing users to choose either DDR4 or DDR5 motherboards, but there was no way it could support a mix of DDR4 and DDR5 on one mobo. It's just unpractical. What I'm asking is not about practicality or reasoning or whatever else that may be smart, it's... to some extent, the opposite, just out of curiosity.

I understand about pin layouts and everything, and that you can't put a DDR3 into a DDR5 slot, and so this is not like "let's do it and test it" type of situation. It's cumbersome to unsolder all these small capacitors and stuff, and there's no real need to, unless you're doing it for an experiment (just like what I'm asking about; asking questions, not to do it). This wouldn't work with a CPU, that is, if you were to remove a die from the same 4770K and 14700K and swap those... that would never work because of different LGA pins and pin layout, like, if there's one pin (or land, or whatever) is ground on the die and the same pin is power... so that's a bit more complicated (and by 'bit' I mean 'everything') so... but with RAM... I understand that they are different types of RAM and everything, but chips are chips, capacitors are capacitors... Or not? Say, if the capacitors on DDR5 can store more and upon soldering them onto DDR3 they blow up because of storing excessive amount of whatever... that's one thing. If it can work (in theory) then... What happens? Does it just take all the energy it can (or whatever it capacitates) and work the same way as on DDR5? Same with voltage regulator and other components.

Finally, here's what I found on Wikipedia: When the memory controller is not on-die, the same CPU may be installed on a new motherboard, with an updated northbridge to use newer memory. (I understand now with IMC's it's irrelevant, but still...) So in theory, at least, say with DDR and DDR3... Would this work?

Again, I understand that with each new generation RAM, as well as any other component, becomes more and more complicated, and while DDR3 may utilize, say, 16 chips for 32 GB, DDR5 may utilize, for example, 4, so that does make it a bit more complicated, but... can it work?! If, say, there are both DDR3 and DDR5 with the same amount of chips and capacity and voltage

Either way, to finally finalize this reply, @Lutfij 's words make the most sense so far... Yet they didn't say much either...

 

[SkyNetRising]

but... can it work?! If, say, there are both DDR3 and DDR5 with the same amount of chips and capacity and voltage

What are we still talking about? It all was answered.

TLDR - your idea is "bad" (really meant something stronger, but moderators might object).
Still clinging to it?
Learn bga chip re-balling. Try your idea and watch your cpu go up in smoke or explode.
Then make a youtube video about it. Might be entertaining. 😊

 

[CountMike]

"Again, I understand that with each new generation RAM, as well as any other component, becomes more and more complicated, and while DDR3 may utilize, say, 16 chips for 32 GB, DDR5 may utilize, for example, 4, so that does make it a bit more complicated, but... can it work?! If, say, there are both DDR3 and DDR5 with the same amount of chips and capacity and voltage"

Is not the reason, with advance in RAM architecture,more transistors could be packed in smaller space and in more layers and work at higher frequencies.
Number of pins is also different and printed circuit too because pins are in different order so you can't just solder different chips to it. What you quoted from Wikipedia doesn't apply any more, IMC is now in the CPU. North bridge (reduced in functions) is part Chipset without physical connection to RAM. Memory sticks do not have dedicated control chip but each chip has own and just provides information (JEDEC and XMP/EXPO) to BIOS without ability to change anything.
Look up the expression "Flogging a dead horse"

 

[miha2]

Number of pins is also different and printed circuit too because pins are in different order so you can't just solder different chips to it.

Believe it or not, that answers my original question in the first place. If you can't just install the DDR3 chips on a DDR5 stick, it's guaranteed not to work. That's exactly what I wanted to hear (or read, in this case). I'm not an expert in what RAM consists of, and I was just curious if this could work, and why or why not. Just "no" doesn't really answer it.

Now, I could go a bit up a level and ask if you were to resolder with copper cord, for example, each pin individually, but then again, different amount of pins, so that will not work, so congrats, you satisfied my curiosity. Thank you