4GB Memory on T61

[Perdu]

I know windows can only use 3GB, but does this limit applications like Photoshop, or can they utilize the extra 1GB?

Sorry if it's a dumb question.

[amstel78]

Application memory access is limited by what the OS can see.

[davidhbrown]

Yup, indeed. I rationalized getting 4GB even though I have plenty of 32-bit-driver hardware I still want to use because (a) it was pretty cheap (US$157 over minimum or some such when I ordered mid-March) and (b) there's supposedly this dual-channel capability when you have matched pairs giving you a performance boost (measurable? don't know).

[erik]

The virtual address space of processes and applications is still limited to 2 GB unless the /3GB switch is used in the Boot.ini file.

source: http://www.microsoft.com/whdc/system/pl ... AEmem.mspx

this applies to windows XP and 2003.   vista may be different.   the above article is from 2005.

[SHoTTa35]

well in a 32bit environment (Vista included) all applications can address up to 2GB MAX. Even if you have 4GB it wont be able to use more than that. In a 64bit environment, they can reach up to 16GB per application.

[erik]

shotta - what about 32-bit apps in a 64-bit environment?   aren't they still limited to 2GB?

[meekus]

Both 3GB (2+1) and 4GB (2+2) configs will run in dual channel (i.e. 3GB = asymmetrical DC, 4GB = symmetrical DC). There isn't a whole lot of gain speed-wise either way in a laptop like there is in a desktop PC so pursuing 4GB for any dual channel speed gains is a waste.

That said, 3GB is more than adequate when running a 32-bit OS. Going with 4GB makes sense typically only when one's going to switch over to a 64-bit OS in the very near future or if the cost of 4GB is the same as 3GB (i.e. one's already got one single 2GB RAM stick installed).

Remember that the biggest speed gain one'll see with either 3GB or 4GB comes from not having to rely on slooooooooooooow paging virtual memory. Speaking of which, on my T60 with 3GB running WinXP Pro, I'm not even running a paging file at all, there are no problems and the performance is noticeably improved over the factory 1GB config.

[SHoTTa35]

shotta - what about 32-bit apps in a 64-bit environment?   aren't they still limited to 2GB?

i can't say i know for sure but i don't think so.

"Basically 32bit Windows is designed so that EACH application can only utilize up to half of the 4GB addressing space, or 2GB. (the other half is reserved for the system)."

http://mpan3.homeip.net/blendermemory

Apparently tho you can set the 3GB switch to allow some apps to go up to 3GB but most will still be hard locked (devs set that) at 2GB. The link above says tho that even on 64bit OS it's only still MAXED at 4GB since most apps aren't LAA (Large Adresspace Aware) or something like that.

[erik]

i know that photoshop can use up to 8GB which is why i'm using vista x64 on my work machines but wasn't sure if the 2GB per app limitation was set by the individual app or the OS.   i'm guessing it's a mix of both.

[Perdu]

Guys, sorry but I'm technically challenged so bare with me:

- Is the Boot ini default for windows to read 3GB, or does it need to be modified?
- My system info shows 3GB. Does this include the Intel Turbo Boost?

Thanks

[erik]

if you're talking about adding the /3GB switch to your boot.ini, don't do it unless you know 100% if all of your applications are compatible with the switch.   since you're asking about turbo memory, i'm going to assume you have vista anyway so the /3GB switch isn't applicable anyway.

addressable system memory does not include intel turbo memory.

[Perdu]

if you're talking about adding the /3GB switch to your boot.ini, don't do it unless you know 100% if all of your applications are compatible with the switch.   since you're asking about turbo memory, i'm going to assume you have vista anyway so the /3GB switch isn't applicable anyway.

addressable system memory does not include intel turbo memory.

Thanks, Erik.