I am using a core2duo, but I figgure for the discussion forum this is just
as good as the x86-64 code is now (or should be) the same between both
processors.

I own several copys of win2k retail professional, as such these keys allow
me to have a few pc's running without any issue. My question here today is,
would I see much of a gain in performance by moving to winxp64, I know a
lot of apps are not yet optimized for the x86-64 or dual core systems so I
hate to make the move as I know there's currenctly no software that i'll use
that would take advantage of the 64bit additions.

Comments are welcome, this isnt ment to be a flame thread so I will take
everything onboard (except GNU os's as I currently require a flavor of
windows that's 2k or greater).

On Sun, 01 Apr 2007 16:48:20 +0000, mr deo wrote:

How much RAM do you have? 32 Bit desktop Windows 2K and XP is limited to
3.5G, if you have 4G of RAM or more you'll want a 64 bit version of
Windows, if you have less than 4G then you'll see 0 difference in
performance between W2K Pro and XP64. There are many different MMU modes
available on the x86 architecture. In the Linux kernel you can select
from the various different modes, 1G addressing, 4G addressing, 64G
extended addressing (36 bit) and 64 Bit addressing. In the Linux world
the 64G 32 bit kernels are usually called Enterprise kernels. For systems
that have 4G or more or RAM that want to run 32 bits you would use an
Enterprise kernel. Microsoft used the 4G mode for their desktop kernels
and reserved the 36 bit mode for their server products. As a result Win2K
Pro and WinXP Pro can't see more than 3.5G of RAM because the IO space
has to map into a 32 bit address space and that eats .5G. I don't know if
they fixed that in 32 bit Vista, they might not have because they intend
the 32 bit version to be a low end product, but there is no limitation in
64 bit XP or 64 bit Vista because those kernels are 64 bit.

* General Schvantzkoph:

The ~3.5GB limitation has nothing to do with Windows. It's simply a BIOS
limitation (traditionally, the address space for expansion cards has to
be located below the first 4GB of memory, and this space is lost for any
operating system no matter if Linux or Windows, and no matter if 32bit
or 64bit. To avoid this most current BIOSes can move the expansion
address space on top of the physical RAM adress space. The setting for
this is often called "new adressing scheme", "modern adressing" or
something like that.

BTW: since this address space is for expansion cards the size of this
space is not exactly 512MB but varies depending on the hardware (usually
somewhere around 384MB, but sometimes also up to 700MB).

Benjamin

On Sun, 01 Apr 2007 20:44:20 +0200, Benjamin Gawert wrote:

It's not a BIOS limitation anymore, it was. Modern BIOSes have something
called memory hole remapping which moves either the IOMMU or part of the
RAM (I'm not sure which) above 4G. 32 bit Linux systems using the 36 bit
physical addressing mode will see all of the RAM. WinXP Pro doesn't
because it's physical address space is limited to 4G which means that it
can't take advantage of memory hole remapping. 64 Bit systems of any
flavor will also see all of the memory because they aren't limited to a
32 bit physical address space, so for Windows users your choice for a 4G
system is either 64 bit XP, Server 2003 (which would be silly for a
desktop because or it's price), or Vista.

* General Schvantzkoph:

Really? It's not that I already wrote that, right? ;-)

Neither the RAM nor the IOMMU is shifted (which is locical because RAM
address space is fixed and the IOMMU is a hardware part). What is
shifted is the address space that is used for expansion cards
firmware/BIOS and I/O. Nothing else.

You can find a pretty good description (made by Sun) here:
<http://techfiles.de/dmelanchthon/files/memory_hole.pdf>

You are mixing two different things here. Of course 32bit XP can't see
more than 4GB memory because it's 32bit and doesn't support PAE like
32bit Linux or 32bit Windows Server (Advanced Server and up). But that
has nothing to do with the problem that only ~3.2-3.7GB of 4GB RAM are
really available in Windowsxp, this is a pure hardware problem...

Benjamin

On Sun, 01 Apr 2007 22:49:19 +0200, Benjamin Gawert wrote:

The CPU supports PAE, XP doesn't, that makes it a software problem. 32
bit Linux sees all 4G because it uses the PAE mode, no thread can use
more than 3G but all 4G is used because there are always multiple threads
running. Microsoft chose not to use the PAE mode in XP Pro because they
wanted to increase the relative value of Server vs the desktop offerings.
In 32 bit XP the RAM is lost to the user, the total available RAM is less
than 4G no matter how many processes are running.

deo> My question here today is, would I see much of a gain
deo> in performance by moving to winxp64,

Almost certainly not, and you probably will see problems with
peripherals that don't have x64 device drivers. If you still want to
try x64, make a dual-boot machine.

--
When I die, I would like to go peacefully, in my sleep, like my
grandfather did. Not screaming and yelling like the passenger in
his car.
- Jack Handey

Hello mr!

01 Apr 07 16:48, mr deo wrote to All:

md> My question here today is, would I see much of a gain in performance
md> by moving to winxp64, I know a lot of apps are not yet optimized for
md> the x86-64 or dual core systems so I hate to make the move as I know
md> there's currenctly no software that i'll use that would take advantage
md> of the 64bit additions.

I also run a Dual 2 core specifically an E6600 so,

Couple of points:

1. Using 64 can and qill cause you problems finding 64 bit drivers. OEM
support for 64 bit Windows is still very light.

2. I'm running Linux both as 32 and as 64 bit. Performance difference is
minimal except when running heavy computations. Disk I/O bound commercial
apps. office type apps such as OpenOffice Word etc would show no improvements
over 32 bit. However running large complex spreadsheets would show better
speed throughput. I have also noted small speed improvements when doing large
compiles.

Hope it helps

Vince.





Vince