Charlie
Thu Feb 15 15:31:06 CST 2007
Actually, I'd disagree at the 4gb point. In most cases, you won't be able to
see past 3GB of RAM on a 32-bit OS. Windows uses a flat memory address
model, limiting 32-bit OSs to a maximum of 4GB of Virtual Memory Address
Space. (I'm deliberately ignoring /PAE for the moment.) Of that 4 GB, 2 GB
is for applications, and 2GB is for the OS. You can force 3GB to
applications, at the expense of the OS, but that has its own costs. And
finally, the BIOS sets aside a block of addresses in the 3-4GB range for use
by PCI device BIOSs. With a 64-bit OS, that BIOS address space can get
shifted up out of the way, and the underlying 2GB limit for applications
goes away. Even 32-bit applications get a full 4GB of Virtual Memory Address
Space. (Many 32-bit apps, however, don't know how to use more than 2GB, so
they will simply ignore the extra.)
My own personal experience says that at 2GB performance is a wash between
32-bit and 64-bit, but that 64-bit has a slight edge on stability. At 3GB,
64-bit is starting to edge past 32-bit. And at 4GB and above, it's clearly
64-bit.
--
Charlie.
http://msmvps.com/xperts64
"BSchnur" <BSchnur@cox.net> wrote in message
news:MPG.203e407a63b3cd83989760@msnews.microsoft.com...
> By and large I doubt you will see a performance gain - probably not
> even with 4G -- for most applications.
>
> The immediate performance winners in 64 bit will be applications
> capable of using 64 bit and those where extra memory (say 8G) really
> can be used by the application.
>
>
> --
> Barry Schnur