Windows 32-bit

An address space is the set of virtual locations on your root drive that an operating system makes available to processes. A fresh 32-bit Windows install right out of the box with 4GB of RAM allows a maximum addressable memory space of 4GB.

On Windows 32-bit the default setting for RAM use is that only 2 GB are made available to processes. The other 2 GB are used by the operating system (virtual address space or virtual RAM). One of the benefits of this separation of allocated RAM for processes/virtual RAM/system hardware* is that if something goes wrong, with RAM allocation types being separated there is security through isolation, e.g., if Photoshop crashes, your operating system and hardware devices will not be affected.

On an operating system with 4GB of RAM the operating system will usually report there is around 3.5GB. Technically one could install 8GB of memory in a Windows 32-bit OS and the system will even acknowledge that that much RAM has been installed but one will still only be able to actually use around 3.5GB of that RAM.

*There will always be about 500MB – 750MB, the kernel portion of your disk, reserved for the use of system hardware devices, i.e., if you’ve installed 4GB of RAM and your system says there is 3.5GB available, your system has reserved 500MB. When you max out your system, the resulting increase in kernel memory overhead can actually reduce the total available RAM to around 3GB. This is why it’s important to shut down unnecessary applications when running RCT3.

Why this 4GB limitation? 32-bit numbers go up to 4 billion. To address each byte of memory the computer needs to have a unique 32-bit number by which to address all the memory that comes in 4GB. So if one has installed 8GB of RAM on Windows 32-bit, 4GB of that RAM will be ignored simply because after the system has addressed the first 4GB of memory it ran out of 32-bit numbers when it reached 4 billion, and the remaining 4GB cannot be addressed because it's already used all the 4 billion 32-bit numbers in existence.

Exploding the 4GB Myth with PAE

Physical address extension (PAE) can allow 32-bit x86 versions of Windows to break the 4GB RAM barrier and support up to 64GB of RAM.

PAE expands 32-bit virtual addresses to 36-bit physical addresses as a result of which there are a great deal more addresses available for the system to use. With PAE your computer ‘thinks’ the physical address space is larger because the page table entries contain longer page addresses. Your system’s API enables this with swap-ins (virtual memory moved into physical memory) or swap-outs (physical memory moved into virtual memory). All this works within 4GB of physical RAM so you won’t need to install more physical RAM to enjoy the benefits of PAE. Your system’s virtual addresses will remain the same though, ensuring that everything in Windows works as it’s supposed to. Notwithstanding this it will still use a maximum of 2GB for each individual active process (although this author has read one report of this figure being as large as 4GB).

As a matter of interest, x86 refers to a family of processors and the instruction set they use. PAE is only used on 32-bit versions of Windows running on x86-based systems. It is not necessary to separately and specifically enable PAE if you have Data Execution Prevention enabled on your system. Let's briefly explore DEP.

According to Windows Help and Support: DEP is a security feature that can help prevent damage to your computer from viruses and other security threats. DEP can help protect your computer by monitoring programs to make sure they use system memory safely. If a program tries running (also known as executing) code from memory in an incorrect way, DEP closes the program.

As it says in the quote, viruses and spyware usually attempt to get around Windows’ process/virtual RAM/system hardware separation of allocated RAM. After launching, sometimes a legitimate application will be shut down by DEP before the process even shows up in Task Manager: addressing this and fixing it is a common way most of us are introduced to the fact that we have DEP on our operating system.

The simplest way to access DEP is to click Start, open Help and Support, and do a search for Data Execution Prevention. You can open DEP from there.

The most convenient way to set up your game in DEP is to select the option to turn on DEP for all programs and services except those I select, and then browse to and add your RCT3.exe file to enable it for PAE.

If it turns out you can't set up DEP in your OS you’ll need to check your BIOS to be sure it’s enabled there.

One can also check if DEP based PAE is enabled by opening a command prompt window and typing in

wmic OS Get DataExecutionPrevention_Available

If enabled you’ll get this response in command prompt:

DataExecutionPrevention_Available

TRUE

If you are unable to set up DEP on your system, to take advantage of PAE you’ll need to download the PAE2 Patch for Windows 7 and Windows 8. Instructions for setting up PAE via patch are available here.

Do keep in mind that patched PAE has had some difficulties in running properly with NVIDIA graphics cards, so if your graphics card is NVIDIA there’s an increased likelihood that you’ll experience problems after setting up PAE with the patch.

Patched PAE also has a problem with some Intel HD Chipsets (Intel iCore) which have finicky drivers.

Remember, although PAE can extend your RAM up to 64GB it will still use a maximum of 2GB for each individual active process, which means that after you have set up PAE either with the patch or through DEP, RCT3 can still only access 2GB of your RAM, whether physical or virtual.

Large Address Aware

If you want specifically to give RCT3 a boost with more than a 2GB limit on RAM or if you have concerns about your NVIDIA graphics card or your chipset, Large Address Aware is another PAE option.

LAA is a third party application that will allow you to easily set up a physical address extension for specific applications.

No installation is required. Simply launch the .exe file and use the dialog to browse to your RCT3.exe file. Check the box to enable RCT3 to use more than 2GB of memory, click on save, and you’re done.

To run Large Address Aware you’ll need Microsoft.NET 3.5 or higher installed.

It is not recommended to use Large Address Aware on systems with less than 3GB of RAM installed; in such instances your operating system will see the changes made by LAA as a mis-allocation of memory which will make your computer laggy.

Memory Remapping

Whether using patched PAE, DEP enabled PAE, or Large Address Aware, your game can be further boosted by with a graphics card that comes with it's own on-board RAM.

Computers less than around ten years old have come with memory remapping enabled by default in the BIOS.  To be sure you're getting the most out of your graphics card RAM you'd do well to check your BIOS to be sure this is so.

With memory remapping enabled your game can access the additional RAM on your graphics card along with along with the additional RAM that has been set up with PAE.

The download link to Large Address Aware is below.