Why Skylake MBPs max out at 16GB - an answer

[BarracksSi]

In case you missed the MR post in the News section:
https://www.macrumors.com/2016/10/28/new-macbook-pros-no-32gb-ram-battery-life/

Following up:
http://www.loopinsight.com/2016/10/31/more-detail-on-the-reason-the-macbook-pro-is-limited-to-16gb/
https://www.reddit.com/r/apple/comments/59yrxg/the_true_reason_the_mbp_doesnt_come_with_ddr4_or/

From Reddit:

So, a lot of people have been disappointed at the lack of a 32gb option.

Apple's statement is true, but lacks detail.

The true reason behind the lack of 32gb or ddr4 is intel. Skylake does not support LPDDR4 (LP for low power) ram. Kabylake is set to include support, but only for the U category of chips. So no LPDDR4 support for mobile until 2018 I think.

One example is the del XPS 13.

On the dell XPS 13 version, you cannot go for 32gb of ram. Meanwhile, the 15 inches does give you that option, but you have to sacrifice battery life for it.

Another example is the surface book, they can't include 32gb. Only goes up to 16gb.

These computers use LPDDR3 which is supported. Many mite make the argument that apple could have used the LPDDR3 version, but how would they look if they did that for the 15 inch MBP only?

Sort of, kind of, a repost, since it was already here at macrumors.com, but I see enough of you guys here in the MB Pro sub forum shouting at Apple for something that Intel is doing (or failing to do).

Anyway, back to your regular bitching and moaning...

 

[tubeexperience]

Sort of, kind of, a repost, since it was already here at macrumors.com, but I see enough of you guys here in the MB Pro sub forum shouting at Apple for something that Intel is doing (or failing to do).

Anyway, back to your regular bitching and moaning...

Sorry to burst your bubble.

Dell XPS 15 with Skylake supports up to 32GB DDR4 2133.

 

[MF878]

Sorry to burst your bubble.

Dell XPS 15 with Skylake supports up to 32GB DDR4 2133.

But it's not LPDDR4, one of the many factors that results in the XPS 15 having much less battery life than the MBP.

 

[tubeexperience]

But it's not LPDDR4, one of the many factors that results in the XPS 15 having much less battery life than the MBP.

DDR4 operates at 1.2 V

LPDDR3 operates at 1.2 V

DDR3L operates at 1.35 V

DDR3 operates at 1.5 V

BS from Phil don't pass the smell test.

 

[MF878]

DDR4 operates at 1.2 V

LPDDR3 operates at 1.2 V

DDR3L operates at 1.35 V

DDR3 operates at 1.5 V

BS from Phil don't pass the smell test.

Yeah, so when you double to 32GB RAM, you basically double power consumption of the RAM, so if LPDDR3 and DDR4 have the same consumption, the point still stands as to why they are choosing not to offer 32GB until LPDDR4 is supported.

If we say for example (I have no idea what the real numbers are) that 8GB uses 2.5W, and 16GB uses 5W, then 32GB would use 10W, and you can see how that starts to become significant.

I find it hard to believe that Apple would've passed up the opportunity to make some margin on 32GB RAM upgrades without there being some technical reason as to why they don't want to offer it yet.

 

[Murgatroyd314]

DDR4 operates at 1.2 V

LPDDR3 operates at 1.2 V

DDR3L operates at 1.35 V

DDR3 operates at 1.5 V

BS from Phil don't pass the smell test.

But that's only half the equation. That's the voltage, what's the wattage?

 

[tubeexperience]

Yeah, so when you double to 32GB RAM, you basically double power consumption of the RAM, so if LPDDR3 and DDR4 have the same consumption, the point still stands as to why they are choosing not to offer 32GB until LPDDR4 is supported. I find it hard to believe that Apple would've passed up the opportunity to make some margin on 32GB RAM upgrades without there being some technical reason as to why they don't want to offer it yet.

LPDDR4 operates at 1.1 V

Are you saying that the memory needs to operate 0.1 V less in order for Apple to put 32 GB RAM?

 

[spacebro]

We know "why" there cant be more ram. The resentment is that they have mislabeled the macbook the "macbook pro" and appear to have killed the real macbook pro.

 

[0388631]

Yeah, so when you double to 32GB RAM, you basically double power consumption of the RAM, so if LPDDR3 and DDR4 have the same consumption, the point still stands as to why they are choosing not to offer 32GB until LPDDR4 is supported.

If we say for example (I have no idea what the real numbers are) that 8GB uses 2.5W, and 16GB uses 5W, then 32GB would use 10W, and you can see how that starts to become significant.

I find it hard to believe that Apple would've passed up the opportunity to make some margin on 32GB RAM upgrades without there being some technical reason as to why they don't want to offer it yet.

Err no. It doesn't work that way. Increasing the size of each chip, not physically but internally, won't change the voltage draw. We're talking the difference of a couple hundred milliampere per hour. Not enough to make a huge difference.

 

[MF878]

LPDDR4 operates at 1.1 V

Are you saying that the memory needs to operate 0.1 V less in order for Apple to put 32 GB RAM?

Voltage isn't the be all and end all, LPDDR4 is also expected to offer more dynamic clock speeds so it only has to ramp up to the frequency required at any given moment.

 

[0388631]

But that's only half the equation. That's the voltage, what's the wattage?

In the days of 1.35 and 1.5 volt banks, they used less than 2.5-3 watts under 100% system load.

 

[MF878]

Err no. It doesn't work that way. Increasing the size of each chip, not physically but internally, won't change the voltage draw. We're talking the difference of a couple hundred milliampere per hour. Not enough to make a huge difference.

It would be the case if 32GB required two modules instead of one, but if not, then your point stands.

 

[Pentium]

Standard DDR4 operates at lower voltage than LPDDR3 (1.20 vs 1.35)

so if LPDDR4 is not supported yet, they should have at least let the 15 inch model uses DDR4!

 

[tubeexperience]

Voltage isn't the be all and end all, LPDDR4 is also expected to offer more dynamic clock speeds so it only has to ramp up to the frequency required at any given moment.

...compare to what?

 

[MF878]

Standard DDR4 operates at lower voltage than LPDDR3 (1.20 vs 1.35)

so if LPDDR4 is not supported yet, they should have at least let the 15 inch model uses DDR4!

View attachment 669518

Oh yeah, I'm not defending their use of LPDDR3 vs DDR4 or whatever, just that it wouldn't have made a difference in their decision to offer 32GB of RAM or not.

 

[0388631]

It would be the case if 32GB required two modules instead of one, but if not, then your point stands.

Depending on the voltage and speed, it may not. In the days of DDR2, the highest performaing RAM which required to overclock the bank, it would draw a head of 7 watts an hour under 100% load. 4 banks would be 28 watts. Boards with more banks could top out at around 50 watts under full system load. A single 32 GB module wouldn't make sense on paper let alone in testing. It's called double data rate for a reason.

 

[Trahearne]

The packages and spec for LPDDR3 and DDR4 are different. If you choose to stick with one type of memory, you are bound to it unless you would like to do two different circuit boards. So now you are asking Apple to design and validate a variant of the circuit board just for an option that perhaps less than 1% of customer would pick.

Moreover, to offer 32GB in MacBook Pro, four 8GB LPDDR3 devices are necessary (LPDDR3 I/O width: x32 or x64). But no one is making these. 4GB is the max in market.

In case people do not know, LPDDR3 is positioned as being more expensive for even lower power consumption than DDR4 (although the gap isn't as large as DDR3-LPDDR3), and LPDDR4 is its successor. The last digit isn't the key here, the LP prefix is.



[doublepost=1477966807][/doublepost]

Standard DDR4 operates at lower voltage than LPDDR3 (1.20 vs 1.35)

so if LPDDR4 is not supported yet, they should have at least let the 15 inch model uses DDR4!

View attachment 669518

Fun fact: LPDDR3 is not DDR3.

 

[Pentium]

[doublepost=1477966807][/doublepost]
Fun fact: LPDDR3 is not DDR3.
Fun fact 2: LPDDR3 is not DDR3L.

yeah my mistake, I though the table talking about LPDDR4/LPDDR3.

 

[leman]

Sorry to burst your bubble.

Dell XPS 15 with Skylake supports up to 32GB DDR4 2133.

Yes, thats exactly what OP wrote. Your point again?

 

[tubeexperience]

Yes, thats exactly what OP wrote. Your point again?

At the bottom, he/she blames not having 32GB memory on Intel.

I just want to point out a counter example.

 

[FrozenDarkness]

At the bottom, he/she blames not having 32GB memory on Intel.

I just want to point out a counter example.

i don't feel like you read the topic at all

 

[evec]

Do you thing Apple don't want your huge upgrade money for 32GB ?

It is 100% because no space for additional memory IC.

 

[clangers23]

I thought Skylake does not officially support LPDDR4, nor does Kaby Lake (except the ultra-low power CPU's)?

Apparently they do work but as it's not an official channel OEM's are not going to support it. Dell have just updated their XPS 13" to Kaby Lake and it has LPDDR3.

I bought a Dell Precision 5510 (workstation version of the XPS 15) a couple of months ago, it came with 2x8 gb low voltage DDR, I purchased 2x16gb DDR4 (which is supported) and it's happily running with 32gb.

Having the ability to swap out socketed RAM over soldered to the board is still a nice to have feature.

 

[FrozenDarkness]

I think fact of the matter is apple didn't prioritize 32gb of ram over battery life and margins. that's just the fact of it. apple does not feel like you need 32gb of ram on a laptop.

 

[jeremiah256]

Do you thing Apple don't want your huge upgrade money for 32GB ?

It is 100% because no space for additional memory IC.

Not sure about that. Apple always seems hesitant to increase RAM, even across product lines. Look at iPhones vs other vendors for example. Why? Could be anything, but I believe it's more that they don't feel the need to pay for costs associated with catering to the 1% who would put out the money for 32GBs.