So CAN XP 32 Bit utilize the whole 4GB? Or only 3.5GB?

[dclive]

Originally posted by: pallejr
I also believe that runnings multiple heavy applications will benefit from pae, they don't need to be coded differently. Only if a single app needs to address more than 2/3 GB must it be coded differently

If you have one app on the box that can do PAE, naturally every other app would benefit a little bit since lower memory thrashing would drop a little bit.

If you have no apps on the box that can do PAE, then no applications would benefit. The apps literally won't be able to use the RAM.

 

[pallejr]

applications don't address physical memory, only virtual. And virtual addresses always lies in 0-4G no matter where in physical memory it points to. So no special coding is needed for that

 

[tcsenter]

Originally posted by: dclive
I don't see how going to RTM or SP1 will fix anything. The same limitations are there too.

XP Professional RTM and SP1 support 36-bit PAE, but are soft limited to 4GB total physical RAM - not physical address space. This means you can access all 4GB via 36-bit PAE on XP Professional RTM or SP1. Perhaps not without glitch-galore, but 36-bit PAE is intact nonetheless (though soft limited to 4GB total physical RAM).

As of SP2, both editions of XP were hard (kernel) limited to 32-bit total physical address space (which implies 4GB physical RAM but is not the same thing).

 

[dclive]

Originally posted by: tcsenter

Originally posted by: dclive
I don't see how going to RTM or SP1 will fix anything. The same limitations are there too.

XP Professional RTM and SP1 support 36-bit PAE, but are soft limited to 4GB total physical RAM - not physical address space. This means you can access all 4GB via 36-bit PAE on XP Professional RTM or SP1. Perhaps not without glitch-galore, but 36-bit PAE is intact nonetheless (though soft limited to 4GB total physical RAM).

As of SP2, both editions of XP were hard (kernel) limited to 32-bit total physical address space (which implies 4GB physical RAM but is not the same thing).

Didn't know that - thanks for the update!

 

[dclive]

Originally posted by: pallejr
applications don't address physical memory, only virtual. And virtual addresses always lies in 0-4G no matter where in physical memory it points to. So no special coding is needed for that

http://msdn2.microsoft.com/en-us/library/Aa366796.aspx

states (among many other things🙂

"AWE does not require PAE or 4GT but is often used together with PAE to allocate more than 4 GB of physical memory from a single 32-bit process."

And yes, I'm aware PAE isn't AWE, but since we're on the topic, it's fair to say the memory can be addressed.

I freely admit I'm no expert on the details of AWE vs. PAE and the overall benefit, but the above is my understanding; can you post a few URLs (from Microsoft) of additional information?

 

[Nothinman]

And yes, I'm aware PAE isn't AWE, but since we're on the topic, it's fair to say the memory can be addressed.

But even when using AWE the addresses that a process sees are virtual and not physical. AWE is just a method for quickly remapping a group of virtual addresses.

 

[nova2]

"And you can watch and see what else breaks when you do that."
if you can, an example would be appreciated, or a hypothetical scenario.

Originally posted by: dclive

Originally posted by: nova2
"unfortunately only applications that are enabled with "IMAGE_FILE_LARGE_ADDRESS_AWARE" header can utilize more than 2GB of the space."

however, you can modify the exe to enable this.

you need editbin from microsoft visual studio
editbin /LARGEADDRESSAWARE filename.exe

i saw people doing this and having success with the supreme commander game exe.

you will also need to edit your boot.ini
add this in: /3GB /Userva=2900

And you can watch and see what else breaks when you do that. There are still drivers out there that make all kinds of assumptions. With Vista (and especially Vista64) that should go away, but still, it's annoying.

 

[dclive]

There are drivers that make assumptions on how Windows will be set up and how the 2GB kernel / 2GB user mode will be set up (that's broken when you switch to 3GB user mode).
There are drivers (nVidia's get picked on a lot, but that's not the only one) that have issues with PAE being turned on.
For examples, Google is your friend. Here's one to get you started: http://forums.nvidia.com/lofiv.../index.php?t19028.html

I'd like to know exactly what changes in the game experience when they make the above modification to the exe. Benchmarks?

 

[nova2]

@dclive:
http://forums.gaspowered.com/v...2&highlight=memory+fix
to prevent crashing due to the limit being reached on the big maps, basically

http://forums.gaspowered.com/v...3&highlight=memory+fix
(FA expansion pack) - You no longer need to use the "MadBoris tool" to address more memory, the largeaddressaware flag was used in linking. This means if you run in a 64 bit OS, you'll get a full 4 GB, and if you tell 32 bit windows to use more than 2 GB, you'll get it.