4GB RAM physical limits and Readyboost

Most consumer laptops have a 4GB hard limit on physical RAM, I'm wondering if you can circumvent that limit using RAM sticks and Vista Readyboost feature. Although it seems unnecessary now it might come in handy for games which need 4GB or more RAM recommended which most laptops simply cannot manage.

 

ReadyBoost is only really for PCs that have 512MB-1GB of RAM and need a boost to work effectively under Vista. If you have 4GB of RAM you really are not going to notice any performance increase at all.

 

What specific laptop are you considering? Most laptops with this limit will not be able to use readyboost to circumvent it.

 

I'd like to hear why you would want to attempt this "circumvent." Are you trying to make a server out of your laptop or something?

 

There's no need to be snide, when I do get a new laptop I want it to last approximately 5 years and increasing the RAM available for games does make a difference even if the GPU is unlikely to get upgraded.

The two models of laptop I'm considering are the Inspiron 1520 and Asus G1S.

 

Neither of those models has a hardware 4GB limit. There is however a practical 4GB limit (due to 2GB sticks being the largest available), and there may be a software 4GB limit (if you have a 32-bit OS). There may also be a BIOS 4gb limit.

 

I know about the practical limit (even worse for my region since Asia-Pacific only goes up to 1GB sticks) and the software limit (I plan for Ultimate x64 eventually) but I don't know how to check the BIOS limit. How does one go about finding that out?

 

You don't. You wait until 4GB sticks are available, plug two of them in, and see if it recognizes all 8GB .

 

Which probably won't happen for me until my planned purchase is halfway down the road of obsolesence. Isn't there an easier way of finding out other than trial and error?!

 

Nope. Officially most laptop's manufactured today have a 4GB limit, however the 965M chipset they're based on should be able to go up to at least 8GB, however that could require BIOS support for 4GB DIMM's, and unless you know how to reverse engineer your laptop's BIOS, then trial and error is about all you have.

 

Could the BIOS support for 8GB RAM be added using a BIOS update?

 

If you want to jump into theory, in the future our HDDs would be as fast as our RAM in memory functions, so you could wait for that to happen.

Otherwise, you aren't going to be getting more than 4GBs worth of RAM anytime soon, nor will you likely need it. Five years is a long time for a laptop, and no amount of RAM is going to make an 8600mGT place Crysis 3 with DX11 well, if at all.

So stick with trying to get yourself two 2GB sticks, and tough it out



Yes the support could be added in most cases, but it would be up to the creator to add that, and they may not, hence the reverse engineering Odin mentioned.

 

Good thing I'm not a fan of the hardware-crushing fps games then. The thread was something I was thinking about and might be useful knowledge to remember in the future.

 

As to the original post-----You're forgetting that 32bit applications have another limitation, of 2GB max for each app.

This limitation is seperate from the 4GB system RAM limit thing.

So even if you run a 32-bit application (like say, Crisis) on a Vista 64-bit box with 16GB of RAM, Crisis can still only use 2GB.

 

woops, double post

 

I've never heard of this limitation, care to back it up or give a reference as to where you read about it? It sounds like something I should know and remember for questions like this.

 

Every 32-bit application exits in a virtual space that includes only 4GB of addresses. Half of those are kernel addresses and half of them are application addresses. Thus any application can only utilize 2GB of memory. A more complete explanation can be found by googling "32-bit limitation". Here's one of the first results:
http://www.brianmadden.com/content/article/The-4GB-Windows-Memory-Limit-What-does-it-really-mean-

 

Ah, so that's what it means. I take it then if games are ever written as 64-bit applications this completely changes yes?

 

Yup, if a game was written as a 64-bit application it would have no practical limit on memory usage (technically it could only use 2^63 bytes, but as that's a ****load of memory, it will be a while before anyone bumbs up against that limitation).

 

I don't know exactly how ReadyBoost was implemented, but I imagine it's more or less like a pagefile. In which case no, it won't help you circumvent this limit. The CPU can only deal with 4GB's worth of memory addresses. Some of them might be mapped to external hardware instead of RAM (typically a harddrive pagefile, or in the case of Vista, a USB stick), but it can never handle more than 4GB.

It's true (for Windows, anyway).
You have a total memory space of 4GB, but obviously, not all of it can be given to your game. Windows needs memory too. Partly for the OS itself, but also for all the services it handles for the game (mapping the GPU memory to system RAM covers up a good chunk of memory addresses, and providing various frame buffers and other directx stuff takes up another chunk)
So for convenience, Windows just divides it 50/50.
By default, I believe Linux uses a 25/75 split, so the OS gets 1GB, and the application 3. In both cases, it *can* be manually adjusted (but I wouldn't do so, you risk system crashes because Windows really does not like running out of memory)

With 64-bit Windows, this changes.
A proper 64-bit game can obviously use all the memory it likes.
But more surprisingly, even a 32-bit game is better off. On a 64-bit platform, it's still limited to 4GB memory addresses total, but this time, there's no reason why Windows should hog the first two. Windows could use GB4-6 instead, and leave 1-4 to the game.
So a 32-bit application, running on 64-bit Windows, can use up to 4GB of RAM before running out of memory.

 

Wow! So that's another benefit of x64. If I read correctly with sufficient onboard RAM an application can use as much as 4GB RAM instead of 2GB for x86 windows right?

 

Yes, exactly. I was mistaken about the 2GB Windows limit carrying over to 64bit versions of Vista/XP (it is "raised" to 4GB there)

 

Anandtech had a fantastic 3 part article explaining this situation.

I suggest reading it.

Part 1
Part 2
Part 3