RAM upgrade on Acer Aspire laptop

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I have an Acer Aspire 5535 laptop, which is running Vista at the moment. I plan to buy Windows 7 Home Premium when it is released which has a RAM limit of 16GB. My laptop has 3GB and I want to upgrade it as much as I can (futureproofing) , but I read online that the maximum is 4GB. Is the limit 4GB because it came with a 32-bit OS, or due to a hardware limitation, and what would happen if I installed more than 4GB?

When it comes to your laptop, it's a limitation made by the motherboard itself. A lot of them don't go past 4GB. Netbooks don't go past 2GB. Attempt to add more than the limit and the laptop will not POST and freeze. Personally I don't see why you'd need more than 4GB though, 2GB is plenty for these days already.

4GB is also the limit for 32-bit versions of Vista, but you only get around 3GB of it.

There are rumors that Microsoft has removed the ~3GB limit on 32-bit Windows 7. If that's true and you don't have drivers that can't handle 36-bit PAE, then even a 32-bit OS can handle >4GB RAM. But seriously, it's about time to switch to 64-bit and forget all these 32-bit limits.

Cloudwalker, the limit comes from hardware. PAE is simply a stop-gap measure. Software cannot defeat physics.

The laptops hardware is 64-bit, and the software will be as well when I get it

It's set by the binary size of the addressable bits; 32-bit is 4G. Since the addressable bits doubles with 64 bits, the actual limit for is somewhere in the terabyte.

Also, some programs as written can't see past 3G, or only with a patch or handle added to make them see 4. 64-bit stuff should.

But as mentioned previously, your system board is what will set the actual limit for you. I've seen more than the actual memory put on a system board once(5G), but the extra Gig isn't seen by the hardware, or the software.

ok, I guess I should have been more specific. There's actually 2 issues at hand here. One hardware, one software.

The hardware limit is mainly determined by the memory controller of your system. On your laptop, that controller is located inside the CPU. Unfortunately, the only spec on memory AMD published for their mobile parts is the speed and number of slots. They do however list their desktop parts as supporting 128-Mbyte to 8-Gbyte DIMM. So it's all guess works whether you can use higher density so-DIMMs on your laptop. Acer's homepage clearly say that the max supported is 2x2GB, but I've seen similarily configurated HP Turion that supports 2x4GB. On the other hand, it's hard to tell if HP used a different steppings CPU or chipset. It's also possible that a BIOS update is needed that Acer simply didn't bother to write. So, if you intended to buy from somewhere that you can't return the goods, you better stick with Acer's limit. Otherwise, it may worth trying. My dad actually asked the salesman in our local computer store to upgrade his laptop to the max amount of memory without knowing how much it can handle some time ago. The thing is if you end up going from 3GB to 4GB only, it may not worth the hassle.

On the software side, if you are ready for 64-bit OS, then there's nothing to worry about except driver and software compatibility. If you want to stick with 32-bit though, only the server versions of Windows will use PAE to address 36-bit of memory. Each process can still only use 2GB directly (3GB if the program supports it and the /3GB switch is enabled). Indirectly, any program can use memory mapped file (this is Windows specific, I've no idea if other OSes has the same effect) and AWE (ie PAE window) to effectively use more memory. Adding Windows itself, the file cache, all those drivers and applications that start automatically together, you won't waste much memory even if you go to 4GB.

With the client versions of Windows though, Windows will only use the first 4GB of memory address. That includes all memory mapped I/Os too, so you can actually use less. But the HD3200 on your laptop don't have its own memory, so on those OSes, you may be able to uses 3.5 or 3.75GB of memory.

Sometimes I suspect MS of coming up with new OS's just to get people to buy new hardware, but wait...that's crazy paranoid talk...

My paranoia joins yours.

And to the person that said MS is making a software 'patch' to make 32bit see more than 3.2-3.75 GB of ram... Yea, then it's not 32 bit anymore. It's a function of the memory controller. The patch forces the software to pretend it's a higher bit than it is, which really all that does is slow the comp down.

I don't think you really understand the situation. PAE is a hardware feature of the CPU. Both Intel and AMD had implemented it on their CPUs long before x64 came out. There is no need to pretend there's more bits, it's actually there in the memory management unit.

The thing that's restricted to 32-bit is the virtual address space. Each process can only see 4GB at a time, of which Windows usually reserved 2GB for itself while Linux usually reserved 1GB. The remaining 2 or 3GB is private for each process. Put it simply, if you have 10 processes running, they can actually use up 20GB (30GB under Linux) of virtual address together. I'm not saying they are but they could. In case you think this is added work, all protected mode 32-bit OSes do this, with or without PAE. It's just that with PAE, they could be backed with physical memory, not just the harddisk.

The real slow down appears when one process needs to use more than 2 or 3GB. It has to ask the OS to move the 4GB window, and those operations are relatively expensive. Note that it's still a lot faster than using the harddisk.

And it's not a 'patch' that Microsoft has to write either, Windows has PAE support since Windows 2000, and all major Linux distro have PAE versions too.

As for the ever increasing hardware requirements of Windows, well I think it takes some real talent to develop software to such a bloat. I mean if Linux can pack so much in a DVD, how come Windows's DVD contains nothing but the OS? And it's not like there's a lot empty space on their disc either.

I was speaking strictly in a hardware sense, no virtual memory.

You don't need anything more than 4GB. Even on a 64-Bit OS I would only go for 6 to 8GB Max. However if you would go beyond 4 GB that will start problems with your model,

Agreed there. In fact, I think there is a lot more on a linux CD than a windows dvd. Probably a big part of it comes from MS' business model of not sharing internally.

Go to crucial.com and put in the make and model of your laptop. They'll tell you how much the hardware can take.