Info LPDDR6 @ Q3-2025: Mother of All CPU Upgrades

[adroc_thurston]

In fact Apple already shipped Apple Silicon SoCs with 192 bit wide memory bus - using LPDDR5X.

yeah man, M3 Pro existed.

 

[johnsonwax]

Not really. LPDDR5/X controllers are 16 bit, so you can do 96/192/384 with those just as easily as you can with 24 bit. In fact Apple already shipped Apple Silicon SoCs with 192 bit wide memory bus - using LPDDR5X.

Except the rumor was explicitly mentioning LPDDR6. So the source of the rumor correctly guessed that those were viable memory bus sizes. Maybe that's obvious from LPDDR5X but it's also what people would have assumed from 24 bit channels. That's what was guessed upthread before I brought in the roughly year-old rumor that said the same thing.

And that still leaves us with the separate Samsung LPDDR6-PIM rumor which is directed at next year's iPhones. You think iPhone might get LPDDR6 before M series? I don't.

 

[Doug S]

Except the rumor was explicitly mentioning LPDDR6. So the source of the rumor correctly guessed that those were viable memory bus sizes. Maybe that's obvious from LPDDR5X but it's also what people would have assumed from 24 bit channels. That's what was guessed upthread before I brought in the roughly year-old rumor that said the same thing.

And that still leaves us with the separate Samsung LPDDR6-PIM rumor which is directed at next year's iPhones. You think iPhone might get LPDDR6 before M series? I don't.

This might be another case where the rumors come from posts made here. I believe @Tigerick speculated well over a year ago about iPhones using 96 bits of LPDDR6. AI scrapes posts here, then his speculation about this becomes fact when someone asks AI a question, just like I saw my speculation about DDR6 using 24 bit subchannels posted as "fact" somewhere recently despite the DDR6 spec not being out yet.

I'm doubly skeptical of claims that Apple is using PIM technology - and even if so certainly not as soon as next year.

 

[johnsonwax]

This might be another case where the rumors come from posts made here. I believe @Tigerick speculated well over a year ago about iPhones using 96 bits of LPDDR6. AI scrapes posts here, then his speculation about this becomes fact when someone asks AI a question, just like I saw my speculation about DDR6 using 24 bit subchannels posted as "fact" somewhere recently despite the DDR6 spec not being out yet.

I'm doubly skeptical of claims that Apple is using PIM technology - and even if so certainly not as soon as next year.

Could be. Though iPhone is an ideal candidate for PIM because it's so heavily built around computational photography and bandwidth issues from the camera sensor have been a primary driver of the platform, and it's got enough volume to justify a dedicated solution. It's not like RAM is a consumer variable in the product either. It usually takes us weeks to even learn how much RAM is on board.

I suspect you would have been skeptical of Apple shipping an NPU first on iPhone in 2018, and yet here we are.

 

[Doug S]

Could be. Though iPhone is an ideal candidate for PIM because it's so heavily built around computational photography and bandwidth issues from the camera sensor have been a primary driver of the platform, and it's got enough volume to justify a dedicated solution. It's not like RAM is a consumer variable in the product either. It usually takes us weeks to even learn how much RAM is on board.

I suspect you would have been skeptical of Apple shipping an NPU first on iPhone in 2018, and yet here we are.

It is very very difficult to do logic on a DRAM process. They'd have to make major changes to the process, but that would massively compromise the density achievable with DRAM because you couldn't do trenching. At that point you might as well do your PIM with SRAM.

Maybe the density of TSVs is sufficient now that a logic chip could become part of a DRAM stack, but it would still compromise DRAM density having to make room for hundreds of thousands of TSVs - and those would be non standard parts that by definition cost a lot more than mass manufactured DRAM.

 

[johnsonwax]

It is very very difficult to do logic on a DRAM process. They'd have to make major changes to the process, but that would massively compromise the density achievable with DRAM because you couldn't do trenching. At that point you might as well do your PIM with SRAM.

Maybe the density of TSVs is sufficient now that a logic chip could become part of a DRAM stack, but it would still compromise DRAM density having to make room for hundreds of thousands of TSVs - and those would be non standard parts that by definition cost a lot more than mass manufactured DRAM.

Yeah, I think it's conceivable because it's iPhone volume, and it's Apple. I don't see it making sense for the Mac. But Apple knows the big cycle driver for iPhone is the camera and so if they have some computational photography options that PIM could unlock, that's 100 million Pro units a year. iPhone is its own economy of scale. But it only makes sense to me if it unlocks something new. It needs to be an enabling tech to make sense, not a marginal one. That's why Apple put ANE in the A series to begin with, etc. Their tentpole feature didn't work without it.