Over the past few years there have been a number of developments in the desktop computer world regarding 64-bit computing. Many of Lumerical's customers have been asking how this impacts photonic design software and how they can take advantage of this technological advancement. This article attempts to answer these questions and get you on your way to employing 64-bit computing to your advantage.

What is a 64-bit computer?

64-bit refers to the number of binary digits inside the processor that are used to represent numbers and memory addresses. Using more bits allows the processor to work with larger numbers and larger amounts of memory. 64-bit computers have been around for a long time, but only recently have they been introduced into mainstream desktop and server processors sold by Intel and AMD. For the remainder of this article, when we refer to 64-bit processors we are referring to the x86_64 architecture processor sold by Intel and AMD, which does not include Intel's Itanium processor.

What are the benefits of a 64-bit computer?

The main benefit of 64-bit processors is that they can handle larger amounts of (RAM) memory than a 32-bit processor. Previous generations of 32-bit processors run into difficulties when the total amount of RAM exceeds 1 GB, an amount that is now routinely found on current desktop systems. Various workarounds allow the 32-bit processors to handle in excess of 4GB of total RAM, but with restrictions. Under Microsoft and Linux operating systems, a single application can not access more than approximately 1-2GB of RAM when using a 32-bit processor, even if the system contains more than this amount of RAM. With 64-bit processors, it is possible for applications to access amounts of RAM that are thousands of times larger than that currently commercially available, effectively removing these problems for the foreseeable future.

There may also be a performance benefit to 64-bit processors when running some applications which can be attributed to legacy issues in the 32-bit processors. As the 32-bit processors evolved, optional performance extensions were introduced periodically such as MMX, 3dNOW, SSE, SSE2, etc. While these extensions can offer significant performance benefits, they often are not used in 32-bit software in order to maintain compatibility with older processors. The introduction of 64-bit extensions has essentially reset the clock on some of these legacy issues since support for most of these extensions is required in 64-bit operation. Software targeting the 64-bit processors can now exploit these extensions to obtain maximum performance without sacrificing compatibility.

Is a 64-bit processor beneficial to photonic design software?

In many cases, 64-bit computers are very useful for photonic design software. Engineering design software often requires processing of large datasets to obtain accurate results. In the past, photonic design software was limited to attacking problems requiring less than 1-2GB, otherwise the software was required to distribute a calculation in parallel across multiple computers in order to gain access to enough RAM memory. Using 64-bit software, it is now possible to solve much larger problems. Note that this does not make parallel computing obsolete; it just separates the problem of accessing large amounts of RAM from parallel processing. Parallel processing is still the most cost-effective way to boost the speed of computations.

Fast Facts

• Current 64-bit desktops and workstations can hold anywhere from 8GB to 64GB of RAM in a single system. Using the 64-bit versions of Lumerical's design tools, you can solve problems that are more than 10 times larger than that which were previously possible with 32-bit computing systems.
• For FDTD Solutions users, larger data sets can now be handled during post-processing analysis, allowing the use of more monitors and more frequency points in broadband simulations.
• MODE Solutions users enjoy an immediate and obvious benefit in that more complex and larger waveguides are now solvable via the removal of the memory limitations for a single calculation.

Which processors are 64-bit?

Fast Fact

Many people who have purchased a new computer in the last couple of years may already own a 64-bit processor, and anyone who purchases a new computer will almost certainly get one

What is required to exploit 64-bit computing?

In addition to a 64-bit processor, you also require a 64-bit operating system and 64-bit application software. The deployment of 64-bit operating systems has lagged the release of the processors, but today most current versions of Linux and Microsoft Windows operating systems come in a 64-bit version. A 64-bit version of your application is also required to perform 64-bit computing.

Need to upgrade your system?

In many cases, it is possible to upgrade a system with a 64-bit capable processor running 32-bit software to a full 64-bit system. This normally requires that you install a 64-bit operating system from scratch, which also means reinstalling all of your applications. Depending on which operating system you are using, you may have to purchase an upgrade from the 32-bit operating system to 64-bit. People who own Windows Vista can change to the 64-bit editions for free, although you may have to order a new media kit from Microsoft.

Fast Fact

Given the importance of 64-bit computing in exploiting current hardware and operating systems, all of Lumerical's products (including FDTD Solutions, and MODE Solutions) are available in 64-bit versions and support all popular 64-bit operating systems.

How can I tell if I own a 64-bit system?

There are various ways to see whether your operating system is 64-bit.

Linux: Check the output of the command "uname -m" if it says x86_64 then you have a 64-bit operating system.

Windows: Open your system control panel. If you are running Windows XP, then under system type you should see "Professional x64 Edition". If you are using Windows Vista, under system type you should see "64-bit Operating System"

If you are running a 32-bit operating system, you may still want to check whether your processor supports the 64-bit extensions. To do this you should determine the model number of your processor and consult the manufacturer's website. Under Windows you can find information about your processor model number in the system control panel. Under Linux you can print information about your processor with the command "more /proc/cpuinfo".

What if I have applications that are not 64-bit?

While all of Lumerical's applications are available in 64-bit versions, not all software vendors have migrated to this technology. In principle, 64-bit operating systems are able to run these 32-bit applications natively, so there should be no performance penalty compared to running on the same processor under a 32-bit operating system. However, there may be other operating system compatibility issues running your 32-bit applications under a 64-bit operating system, so you may want to check with your application vendors before upgrading.

Fast Fact

It is important to note that running a 32-bit application under a 64-bit operating system is no different than running it on a 32-bit operating system as the same 32-bit memory and performance limitations still apply.

Why do vendors sell 64-bit processors with 32-bit operating systems?

When purchasing a new computer, you may find that the default operating system is a 32-bit edition even though the processor supports 64-bit. This is especially true for desktop systems. The reason for this is that many desktop applications don't benefit significantly from the extended memory support on 64-bit systems, and there is some risk of some compatibility issues with 32-bit desktop applications. You may have to specify to your vendor that you would like a 64-bit operating system for your new system. It is more common to find 64-bit operating systems offered on servers and workstations since applications for these systems have migrated more rapidly to the 64-bit platform.