64-bit MacBook Pro notebooks may take up to 16GB of RAM | Hacker News Reader

64-bit MacBook Pro notebooks may take up to 16GB of RAM

powerpage.org

21 pointsdavethenerd11 comments

This has only ever been a chipset limitation. Not that long ago there were 64-bit capable Nvidia chipsets that could still only address 3GB of physical RAM due the way they mapped device memory into the system address space [1].

Sandy Bridge processors contain their own memory controllers that can address 16GB-32GB of RAM. True for any system they're in, as long as all channels are linked to physical DIMM slots [2].

[1] http://blogs.msdn.com/b/hiltonl/archive/2007/04/13/the-3gb-n... [2] http://ark.intel.com/

Hmm, your links imply that my old Inspiron 6400 might be able to take two 2 GB modules (the manual says it can handle a 2 GB module) and have access to something more than 2GB of addressable RAM. Anyone happen to try this with this or a similar model Dell? (The 6400 is equivalent to the 1505, IIRC. Its manual says it's limited to 2 GB of RAM.)

EDIT: Answering myself, it appears it can take 2 x 2 GB sticks. The following Dell forums thread describes this, although this particular post linked claims that the configuration will disable dual channel memory access (but then again, other posters are happy and view the expansion as an improvement).

http://en.community.dell.com/support-forums/laptop/f/3518/p/...

EDIT2: I've seen some other comments that dual channel remains enabled (with matched 2 x 2GB sticks). I guess I'll give it a go.

Well known. Here are kits for MacBook Pros:

http://eshop.macsales.com/shop/memory/Apple_MacBook_MacBook_...

I recently found out that I could upgrade my late 2008 MacBook Pro to 8GB of RAM. The specs say only 4GB will work, but soon as I found out that 8GB should work I upgraded for just $50.

You need an EFI firmware update that you may have already installed. Read more: http://www.macrumors.com/2011/03/07/secret-firmware-update-u...

If I understand correctly, more RAM draws more power.

Anyone have an idea of the hit to battery life caused by going to 16GB?

The biggest draw on a battery is current. I don't believe that RAM draws very much current, otherwise they would need fans to dissipate heat. Your screen's brightness likely has more of an effect on your battery life than doubling your RAM from 8GB to 16.

What's the second biggest draw on a battery?

no, more ram means less power consumption because you are accessing hard drive less often.

For what it's worth, the OpenBSD team is working on improved buffering for high-RAM machines:

"Computers today have immense quantity of unused memory. This new software almost works, we still have some minor bugs to fix, but the results so far are incredible. On computers with 16GB of RAM we can dedicate as much as 13 GB to buffering and almost no data is read from the hard drive, everything is in the RAM. It performs even faster than SSDs. We only have to write to the disk anymore and that’s mainly for reliability reasons. I estimate we’re a year away from the whole thing working flawlessly. From this aspect the 6 month release cycle is a bit limiting."

http://undeadly.org/cgi?action=article&sid=2011101806163...

seriously, you think OpenBSD invented the buffer cache?

Pretty sure that's wrong except in contrived disk-heavy workloads. RAM needs power in proportion to its storage size.

My 2009 MBP, which I immediately upgraded to 8GB RAM on purchase, has never come close to the stock advertised battery life. And, supposedly a reason Apple optimizes iOS devices for such small RAM sizes (sizes which are never emphasized in published descriptions) is that minimizing RAM is an important factor for their long battery life.

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