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I saw some already asked if its possible to install more than max. specified RAM capacity. I want to go a bit further.

I have a laptop (Vaio VPCF11C5e) with currently 2x4GB 1066Mhz installed. According to this is the maximum - as well DDR3-1066 as 8GB. I want to put one (or two) 8GB SoDimms in there. (As far as I know single 8GB SoDimms have at least 1333Mhz)

In the end I don´t want to get a faster Ram or more of it - I want to use the additionally Ram as a Ramdisk. So the CPU will have only 8GB Ram to deal with, but will have to address 16GBs Ram. (as says, the Physical Address Extensions is 36bits which would be 64GB)

The biggest problem I see would be the configuration of the Ramdisk and/or booting generally with too much ram.

Does anybody have exerience with this issue - or did I make a mistake?

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closed as not constructive by Ƭᴇcʜιᴇ007, Tog, Brad Patton, afrazier, Karan May 17 '13 at 1:17

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If the manufacturer tells you that is the maximum addressable RAM for that system, then it is the maximum amount the system will ever see. It's hardwired into the MB and nothing is going to change it. – Fiasco Labs May 13 '13 at 16:39

You need the CPU to support the RAM you want to use so it can be seen/addressed/used by the system.

Your CPU supports up to 8GB, so you can only use 8GB of RAM (regardless of what you're using it for).

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Of course, but the question is also why is it limited to 8GB if its not because of addressing so much space... – Voltobene May 13 '13 at 16:45

It may well be that the CPU only has enough pins fitted for it to be able to support 8gb. If that is the case then it is a very hard limit that can only be changed by changing the CPU.

I've written about this before in another question here

Think of it this way, in order to support 4 GB of ram your memory controller needs 32 address lines pulled out, to support 8gb you need 33 lines. But modern CPUs use dual channel configurations to improve performance so each of those channels needs 32 lines for 4 GB each, giving you 64 total lines needed for 8gb of dual channel memory or 66 lines for 8 GB per channel. More lines/ more channels just means more pins on the CPU, something which can be at a premium already with several different data busses and power lines needed to make it work in the first place.

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A Cpu that supports 16Gb (or more) doesn´t (necessarily) use more pins for Memory Access than mine. See i5 2.Gen..... – Voltobene May 13 '13 at 19:14
Pin count doesn't necessarily take into account how many of those pins are actually connected either, each one of those connected pins requires a length of wire going between the pin and silicon and the cpu designer may not have thought it worth the effort. As the memory controllers are now on-CPU this is almost certainly a hard cpu limit rather than a motherboard limit. – Mokubai May 13 '13 at 19:29

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