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What limits a motherboard from supporting more memory?

I have a netbook (HP Mini 110) with limited RAM. It shipped with 1 GB and according to HP that's all it can handle. Yet I've read here that it's possible to upgrade at least some models of the series to 2GB.

This raises a question: How can one determine the true hardware- and/or BIOS-imposed limit on the amount of RAM, and what factors contribute to said limit? I'm specifically excluding OS-imposed limits, as such issues can be worked around for people who are willing to switch OSes as necessary. Please also bear in mind that I don't know too much about hardware; I'm a software guy.

EDIT: According to the comments, the motherboard is a potential limiting factor here. Why? What makes the motherboard (or some other component) consider a 2 GB stick to be OK, but not a 4 GB stick? Basically, I'm trying to understand the technical reasons behind memory limitations.

Info about my specific situation: I'd like to upgrade to 4 GB if possible, but I don't want to waste money. However, this question isn't really about my specific hardware; it's more general than that. While I'd be interested in hearing any personal experience with my particular hardware, I think that kind of stuff is best for the comments, as this question is the one in bold above.

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marked as duplicate by studiohack Nov 30 '11 at 22:06

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

It would be based on which motherboard they used. Can you tell us how many memory sticks it currently is using? – Ramhound Nov 28 '11 at 15:48
You will want to purchase a single 2GB stick of PC6400 which is the max your netbook will support. – Ramhound Nov 28 '11 at 16:45
@Ramhound: Thanks for your comments. I haven't opened the case, but judging from the size of the RAM compartment, it appears that there's only room for a single stick. – Scott Severance Nov 28 '11 at 23:23
@Ramhound: I'm updating my question to clarify it a bit. See above, please. – Scott Severance Nov 28 '11 at 23:23
Found a similar question: What limits a motherboard from supporting more memory? – Hand-E-Food Nov 29 '11 at 23:07
up vote 2 down vote accepted

As a software developer, you can't design software for Windows 9 or Mac OS 11, because neither of those operating systems have any released specs. When the operating systems do come out, they might run your software, but you certainly can't design your software to support those operating systems.

One of the main limiting factors is that the interface for a larger capacity memory chip, or any other piece of equipment, must be designed in the motherboard. It's likely the motherboard was designed to only use memory chips that existed at the time and could be tested thoroughly with the system. Even if better chips were released before the motherboard was released, the motherboard's design phase happened long ago.

Supporting a wider range of chips also increases design costs, manufacturing costs, testing costs, and ultimately, consumer costs. The motherboard can only support a so-good processor, so there's little point supporting RAM that isn't within similar specs of the processor. No one is going to use 8 Gb of RAM with a slow processor, or 1 Gb with a turbo processor.

It's a waste of money to design a motherboard with overly-broad capability.

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Thanks for your answer. I find it surprising that all memory sticks of the same type don't use the same interface. For example, consider a stick of DDR2 running at a given speed. Is it necessary to change the interface simply because the capacity is different? Can't the interface have some way of reporting the capacity? Or am I missing something fundamental here? – Scott Severance Nov 29 '11 at 6:48

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