Cheat Engine

SFP+ · Last edited by SFP+ on Mon Nov 28, 2016 5:05 am; edited 7 times in total

Seeing as I've seen quite some threads / posts regarding this matter, I thought I'd just let you know;

How graphics cards and other devices affect memory limits
Devices have to map their memory below 4 GB for compatibility with non-PAE-aware Windows releases. Therefore, if the system has 4GB of RAM, some of it is either disabled or is remapped above 4GB by the BIOS. If the memory is remapped, X64 Windows can use this memory. X86 client versions of Windows don’t support physical memory above the 4GB mark, so they can’t access these remapped regions. Any X64 Windows or X86 Server release can.

X86 client versions with PAE enabled do have a usable 37-bit (128 GB) physical address space. The limit that these versions impose is the highest permitted physical RAM address, not the size of the IO space. That means PAE-aware drivers can actually use physical space above 4 GB if they want. For example, drivers could map the "lost" memory regions located above 4 GB and expose this memory as a RAM disk.

Dark Byte · Posted: Tue Mar 31, 2009 11:23 pm Post subject:

Actually, there are tools that do make it possible to access the lost memory
If you enable PAE paging you can address up to 36-bit of memory (64GB ram)
As you said, the videocard memory is in the lower 4GB ram, but the extra ram isn't lost. It's remapped to above 4GB.
With certain api's you can actually map this physical memory in 32-bit and make use of it (vista) .
On older os's like xp you don't have those api's BUT with some playing around in the kernel you can still make use of it. (Just edit the pagetable directly and set physical address to point to the memory above 4GB, just like the RRamdisk tool does, which is a nice tool and useful as a place to store the swapfile)

Sure the process itself won't be able to use more than 2 or 3GB ram, but at least you won't be having to deal with memory getting swapped out and losing performance. Just adjust the memory window if you need to access another part of the upper 4GB of ram

I have 6GB of ram and actually use the lost 2.7GB of ram as a Ramdisk when using 32-bit windows

superweapons · Posted: Wed Apr 01, 2009 9:25 am Post subject:

I believe Microsoft still put restrictions on the 36-bit PAE extended memory mapping area to 4GB, up by a few hundred megabytes. The limitation is for XP as far as I'm concerned, system RAM should still report about 3.5GB with PAE enabled, alongside the other memory on your computer. Windows Server Editions PAE map up to 64GB.

Last time I checked, Vista didn't have any kind of PAE support. But SP1 patches x86 versions to display up to 4GB of RAM, although the amount of usable RAM is still limited.

Jani · Posted: Tue May 19, 2009 7:26 am Post subject:

http://www.geoffchappell.com/notes/windows/license/memory.htm

powerfear · Posted: Mon Jun 29, 2009 8:59 am Post subject:

well i think this could clarify maximum ram for every windows version...

http://msdn.microsoft.com/en-us/library/aa366778%28VS.85%29.aspx

Polynomial · Posted: Mon Aug 10, 2009 2:59 pm Post subject:

Whilst the physical memory limit for a 32-bit OS is in fact 4GB, the OP fails to take into account that there is a 2GB memory barrier for user-mode processes. Each process in 32-bit Windows can only access 2GB of physical memory.

However, as Dark Byte stated, if PAE is enabled on a 32-bit operating system the maximum amount of physical memory that can be addressed is 64GB. Normal processes will still stick to the default 2GB barrier (unless 4GB Tuning is enabled, see below), but specially design applications will be able to take advantage of the Address Windowing Extensions API to increase the amount of memory that they may access.

You can also specify the /3GB switch in boot.ini to enable 4GB Tuning. This allows applications compiled to be large address aware (using the IMAGE_FILE_LARGE_ADDRESS_AWARE flag in the image header) to access up to 3GB of physical memory. The downside is that this reduces the amount of memory available to the system down from 2GB to 1GB.

noko_112 · Posted: Mon Sep 07, 2009 10:46 am Post subject:

What is the max for a 64 bit sys. I know it high, but how high?

superweapons · Posted: Mon Sep 07, 2009 2:40 pm Post subject:

Windows Vista Ultimate (as well as a few other high-end editions and some Server 2008 offerings) x64 is 128GB I believe, and Windows 7 Ultimate/Enterprise/Professional x64 is 192GB. Home Premium for both W7 and Vista is 16GB.

I'm not sure about Linux, but Snow Leopard (running 64-bit EFI and enabling the 64-bit kernel components) is 16TB.

yadsendew · Newbie cheater Reputation: 0 Joined: 25 Jul 2007 Posts: 10

oh my god why would you ever need 16 TB of ram

Karakawe · Posted: Tue Sep 08, 2009 1:09 pm Post subject:

It would be a complete waste anywhere. It was just the logical step from 32-bit architecture, which actually does have an easy-to-reach limitation on memory.
Also, Linux is 16TB as well, as far as I know. Although in theory, you could be able to access more...

hcavolsdsadgadsg · Posted: Tue Sep 08, 2009 4:32 pm Post subject:

CPU's generally only allow up to 40-48 bits of memory to be accessed, probably for die space savings among other things as the amount of ram you can actually access goes from FUCKING SILLY to merely LUDICROUS.

Slugsnack · Posted: Sun Feb 28, 2010 7:35 am Post subject:

paupav · Posted: Wed Sep 21, 2011 8:06 am Post subject: Re: Regarding RAM space at 32bit

so i'm upgarading my old PC... because its fun...
i ve bought 1 gb ram (omg ddr1 is 3x more expensive than ddr3 why?) and i will buy new gpu and i need example 512mb to run game and if my new gpu takes 512 mb i will not be able to run it... why gpu doesnt take it from virtual memory instead of RAM memory?

Dark Byte · Posted: Wed Sep 21, 2011 10:33 am Post subject:

It doesn't TAKE ram, it just moves the available ram to over the 4GB limit. See it like a fat guy cutting in a row pushing the last guy of the row into an abyss

So if you have 1GB ram and buy a 512MB video card you will have 1.5GB RAM, of which 512MB is videocard ram only (so only 1GB available)
basic memory setup: (does not include the other special regions like APIC and ROM's)
0-1.0GB=available RAM.
1.0GB-1.5GB=Videocard RAM
1.5GB-> Does not exist

4gb example:
If you have 4GB ram and buy a 512MB videocard, you will have 4.5GB RAM.
basic memory setup:
0-3.5GB=available RAM.
3.5-4.0GB=videocard RAM
4.0-4.5GB=available RAM (but to access that in 32-bit you must have a 'special' license with microsoft)
4.5GB->Does not exist

paupav · Posted: Sun Oct 02, 2011 5:15 am Post subject: