Adding more RAM than there should be??

[JDN]

I didn't really know what to title this thread. I have a couple of questions, one for my own personal knowledge and another leading from that.

1) What limits the amount of RAM that a computer can hold? I know there is the physical limit of slots, but what else limits the amount of RAM?

2) Is it possible to *hack* (i don't like that word) or modify a computer in some way to allow it to take more RAM?

So to hypothisise, i have a MBP CD 2GHZ 1Gb RAM 80GB HD. Now on the fact sheet, it says the maximum RAM you can put in is 2Gb, but would it be possible to put more in? By using 2Gb RAM cards or some other combination.

I know nothing about this side of computers, so if someone could explain it simply that would be really great.

Cheers.

 

[mattscott306]

Macbook pro's can handle 3 gigs of ram. I beleive it has something to do with the software as to why they couldn't handle four. I'm thinking four is probably gonna be the limit on the current revision of these babies.

 

[JDN]

Macbook pro's can handle 3 gigs of ram. I beleive it has something to do with the software as to why they couldn't handle four. I'm thinking four is probably gonna be the limit on the current revision of these babies.

I thought CD could only handle 2Gb and C2D 3Gb???

 

[mattscott306]

I thought CD could only handle 2Gb and C2D 3Gb???

Misread that, thought you said C2D. You are Correct.

 

[plinden]

Macbook pro's can handle 3 gigs of ram. I beleive it has something to do with the software as to why they couldn't handle four. I'm thinking four is probably gonna be the limit on the current revision of these babies.

It's to do with the address space that can used by the Intel chipset. It has a maximum of 4GB, but close to 1GB of the address space is reserved for other system components. http://blogs.zdnet.com/Apple/?p=321

 

[yippy]

In the Macs case it has nothing to do with software. The Mac Pros run the same software and can handle 32Gb.

That said, it is a combination of both hardware and software. A 32bit processor can only handle 4Gb of ram total. This a theoretical limit and other things can limit it below that. In the case of the MacBooks (Pro) the limit is in the memory controller on the mother board. For whatever reason, power and/or cost, they have been built with an addressing system that can only handle 2 or 3Gb of ram.

Some systems, like the PowerMac G5 and a few models of the original iMac, were limited simply by the size of available ram chips at the time. When denser ram chips became available it was found that the systems could hold more than Apple claimed they could. Unfortunately this is very rarely the case.

 

[Sherman Homan]

Thousands of years ago the Mac Plus had an address space limit of 2.5 megs out of the box. If you wanted to spend hundreds of dollars and get 4 one meg 32 pin ram chips you had to clip a resistor on the logic board.

The ability of a computer to handle ram is a combination of the operating system software and the logic board hardware. Sometimes the applications can impose their own limits.

 

[JDN]

So what would happen if i put 3/4Gb of RAM in my MBP CD? Would it just not get recognised?