So Vista can’t use the memory it insists on hogging? Why? No wonder it’s under-performing.
64 bit versions of Vista can access massive quantities of memory. The 32 bit version can address 4GB of memory.
3GB is the practical limit for 32 bit Vista since 1GB is reserved for video memory, bios, etc.
It is just like the 640kB limitation under DOS. DOS could address 1MB of memory, but had to reserve 360KB for video and bios.
The amount varies with hardware. There is no "hard" number of how much is wasted due to peripheral addresses.
I would also assume Linux is under the same restrictions as Windows and other 32bit operating systems.
Actually, it’s 2GB. There is a boot option to allow you to use 3, but it won’t work. But Dell will sell you 4 GB. Ask me how I know :)
IIRC, the Windows NT kernel beginning with Win2k can address up to 4 TB of memory.
64-bit Vista can handle 16 exabytes, so it's really only limited by how many chips you can put on a motherboard. However, it's artificially capped for the Home versions (8 and 16 GB, thanks Microsoft for breaking your OS to achieve market segmentation).
While 32-bit Vista can handle up to 4 GB RAM, various devices like video cards are counted as addressable memory, so they eat into it. Count on losing the ability to address about 512 MB of your RAM because of this (maybe more depending on your hardware), so 3.5 GB is really the limit of usable memory for your applications. In any case, no one application can be assigned over 2 GB RAM.
But, (there's always a "but" in computers), some hardware can let 32-bit Windows use more than 4 GB RAM through physical address extensions (sort of an extended memory hack). This setup is common on 32-bit Windows Server 2003 implementations. I don't know whether regular 32-bit Vista does this too.
In any case, you really need to be running a 64-bit machine, OS and software if you want to use that much memory.
You can access a maximum of 4GB RAM on a 32 bit machine. 64 bit will take you higher.