Hacker News Reader

Comment by Alex3917 | Hacker News Reader

The reason you can't get 32 gigs of memory is because Skylake (and Kaby Lake) don't support mobile DDR4 memory, which is necessary to make power consumption low enough for a laptop. This isn't Apple's fault. Short of making a 7 pound windows-style gaming laptop, there's not really much that they can do until 2018 when Cannonlake comes out.

View on HN

Bologna. Dell and system 76 offer current and last gen Intel processors in excess of 16 GB of RAM going up to 64 in the case of system 76.

Yeah, but what sort of battery life are they getting? It's not that you can't have more RAM with those processors, it's that you can't have more energy efficient mobile RAM.

Is it possible for a machine to dynamically turn the power to RAM blocks on and off?

In periods of low use, the OS may choose to swap most of the RAM to disk and switch it off to save energy.

You can't turn off blocks of memory in a single RAM chip AFAIK, it's all or nothing. And I think enabling and disabling different RAM chips wouldn't be very viable since you'll need to move memory from one chip to another when turning one off, there would be a lot of potential issues when that happens.

However enabling and disabling RAM chips and rebooting the laptop, like a low-power toggle, would be possible.

Hot swapping RAM has been possible for a very long while in software, though originally built for servers. Apple, with their tight control over the hardware, could likely have also modified the power management controller and whatever other hardware that needed modifying to pull something like that off.

It's rumored that the Surface Book 2 will use Kaby Lake and have a 32GB option. So does this mean the only way MS can support that is by increasing size and weight to 7lbs+?

Well either they need to use a lower TDP cpu/gpu or else make it bigger. Either way, TANSTAAFL.

Any reason why they couldn't use SODIMM DDR4? It's 1.2v of DDR4 vs 1.2v of LPDDR3.

I would like to see some hard facts instead of everyone simply quoting what a marketing person from Apple had to say.

IMHO, it's just that they didn't really didn't want to go through the trouble - the % of their target users requiring 16GB+ isn't that large.

Razer's Blade Stealth is on Kaby Lake now, and it's basically a macbook air form factor with excellent battery life http://www.razerzone.com/gaming-systems/razer-blade-stealth

So? The Blade Stealth maxes out at 16GB.

Do you have a link about the technical properties of "mobile DDR4" memory? Lenovo T460p has 32GB RAM, DDR4 RAM and a quad-core Skylake i7 CPU with 4lb weight and a claimed 10h of battery life.

Just google Skylake LPDDR4. Or Kaby Lake LPDDR4.

For whatever reason, Skylake doesn't support LPDDR4. And the Kaby Lake refresh isn't going to include chips suitable for the MBPs, but even if it did they also won't support LPDDR4.

Mobile DDR4 == LPDDR4.

Apple went with LPDDR3 which those chipsets do support to increase battery life. I would have rather they'd gone the other way.

Reply on news.ycombinator.com