Graphics hardware requirements and recommendations


General recommendations

The summary here is just for your reference, so you can get a feeling on what to expect with specific hardware. If you buy new systems, go for the latest generation hardware of NVidia or ATI. Currently, stuff that claims to support Direct3D-10, OpenGL-3 or ShaderModel 4, does support all functionality of Psychtoolbox in the most optimal way. All cards of the NVidia GeForce 8 series and later (e.g., 8600, 8800, 9600, 9800, GTX 280 etc.), as well as all cards of the ATI Radeon HD series and later (HD 2400, 2600, 3000 series, 4000 series etc.) and their corresponding counterparts from the NVidia Quadro series and ATI FireGL / FirePro line of cards are technically state of the art and Psychtoolbox can take full advantage of their useful new features. Expensive high-end models differ from cheap low-end models almost only in raw performace, i.e., drawing speed, not in functionality, unless stated otherwise below.

Mobile graphics chips (in Laptops) are almost always slower than discrete graphics cards in desktop computers. This is a design tradeoff to accomodate the stricter requirements for cooling, space and power consumption in portable computers.

So called “integrated graphics chips” (aka “onboard graphics chips” or “chipset graphics” or IGPs) are usually cheaper and consume less power and space in a computer, which is why they are often found in Laptop computers and cheap desktops. Their disadvantage is usually much lower performance. The latest onboard parts from NVidia and ATI provide the same or almost the same features as dedicated graphics cards, so there isn’t a limitation in functionality per se. The raw processing power is lower though, because these chips often don’t have dedicated fast VRAM memory, but share slow RAM system memory with all other parts of your computer. They usually also have less processing units (so called shader processors or stream processors). All in all they may be sufficient for many not too demanding tasks. Very compute intense, image processing intense or memory intense tasks may not be feasible in practice because although they are doable in principle with the given feature set, the raw performance is just pathetically insufficient for research grade realtime behaviour. They are usually perfectly sufficient for designing and debugging your experiment scripts, where absolute realtime performance doesn’t matter.

Tested graphics hardware + operating system configurations

The following combinations of graphics hardware and operating systems are used by the developers for development of PTB-3’s Screen function and therefore tested and known to work well within their respective feature set. This doesn’t exclude other similar or more advanced system configurations which likely will work equally well or maybe even better. It just happens to be the equipment that is accessible to us for development and testing. As a rule of thumb, a specific feature of a specific piece of graphics hardware that works well on MS-Windows will likely work equally well on GNU/Linux and vice versa due to the unified drivers used for these operating systems (drivers for Windows and Linux by ATI and NVidia are derived from the same code base). This is not necessarily true for Win/Linux vs. Mac OS X, because the OpenGL drivers for OS X are developed by different development teams from a different code base - Apple imposes a much stricter control over their implementation of OpenGL, with different priorities wrt. feature set. This means that the same gfx hardware may expose different functionality, performance, limitations and bugs on OS X vs. Win/Linux due to fundamental driver differences.

The following setups are used for development and testing of PTB, so they get tested for compatibility at least once for each beta release

  • ATI Radeon X1600 mobile chip in a Apple Intel MacBook-Pro, currently running OS X 10.4.11. Dual display support tested. This is the current main development system for PTB, so it gets tested on a daily basis and for each beta release. The same system gets tested for each beta release under Linux Ubuntu 7.1.
  • NVidia GeForce 8800 Ultra in a Apple Intel Mac Pro, currently running OS X 10.5.6. This is one of the main testing and productive systems.
  • NVidia GeforceFX-5200 desktop graphics in a single processor PowerMac-G5, under OS X 10.4.11. This is one of the main testing systems.
  • NVidia GeForce 7800 Ultra in a Dell PC running Windows XP SP-2/3. This is one of the main testing systems.
  • NVidia Geforce2Go/GeforceMX mobile graphics chip: Regularly tested under Windows 2000 and GNU/Linux in a Dell Inspiron 8000 laptop. Dual display support tested under Windows.

These cards get tested infrequently, i.e., if significant changes inside Screen() indicate need for testing and if the systems are available for testing:

  • NVidia GeForce 8800 Ultra under Windows XP.
  • Quadro FX 4500 under Windows XP. Dual display support tested.
  • NVidia QuadroFX-5800 under Ubuntu Linux 8.1.
  • Radeon HD 2400 under OS X 10.4.11 in a Intel Mac.
  • Intel GMA 950 of Apple MacBook. Tested once under OS X 10.4.
  • Nvidia Geforce 6800 mobile chip in a high end Dell Laptop under Windows XP and GNU/Linux tested once. Dual display support tested.
  • Intel GMA 945 onboard GPU: Tested exactly once in single-display mode on a Dell PC under Windows XP, also tested once under GNU/Linux. A similar class would be the ATI Rage 128 / Pro in very old Apple Macintosh computers.
  • NVidia Geforce4 desktop graphics chip tested once under GNU/Linux. Geforce3 series hardware should behave the same. Also tested once in a standard Intel PC under GNU/Linux and Windows XP. Dual display support also tested.
  • ATI Radeon 9600 under Intel laptop with Windows-XP, tested once.

Rough lineup of different generations of graphics hardware with their respective features

Basic OpenGL 1.2 compliant hardware

These provide the minimum amount of functionality for use with Psychtoolbox:

  • Frame accurate stimulus onset timing, animation timing and high precision stimulus onset timestamping generally works well, as long as you don’t try to overtax the hardware.
  • Some of these cards do provide full dual-display output support, e.g., for binocular stimulation.
  • All basic 2D and 3D drawing functions work with useable performance for simple tasks.
  • Limitations: Drawing of image textures works, but drawing speed may be rather low and use of texture memory inefficient (so you can use less textures or offscreen windows simultaneously). Drawing to and handling of offscreen windows is rather slow and inefficient. Precision for scrolling of textures (e.g., for drifting gratings) may be rather low. Image anti-aliasing is functionally limited to points and lines, slow and of low quality.
  • Psychtoolbox imaging pipeline and support for procedural textures completely unsupported.

The limitations are due to lack of programmable shader support, lack of support for framebuffer objects and lack of support for rectangle textures. Typical examples of such hardware are: All ATI Rage 128 (Pro) and older, all Intel chips older than the GMA-950, all NVidia chips before GeForce-2.

Hardware with additional support for rectangle textures

  • Improvements: These support efficient storage and fast drawing of textures and offscreen windows, incremental speed and quality improvements in anti-aliasing and general performance.
  • Remaining limitations: No support for imaging pipeline, no support for procedural textures, rather slow drawing into offscreen windows. Only point and line anti-aliasing.

Typical examples are all NVidia GeForce hardware from GeForce-2 series upto GeForce-4 series, all ATI Radeon hardware upto Radeon 9200.

Hardware with support for framebuffer objects and programmable shaders (Shader model 2.0)


  • Fast, efficient support for offscreen windows: Efficient use of memory, fast drawing of and into offscreen windows and textures.
  • Basic support for the imaging pipeline, e.g., geometric display undistortion, and almost all stereo display modes (dual display, very flexible and high quality anaglyph stereo, interlaced stereo).
  • Support for simple procedural texture stimuli via GLSL shaders.
  • CLUT palette animation and image data conversion via simple mathematical functions or lookup tables. Basic GLSL Vertex and Pixel shader support (Shader model 2.0).
  • High quality multisample anti-aliasing on all non-Intel graphics chips. Frame-Sequential stereo under OS X on all graphics cards except Intel chips.

Typical examples are all NVidia GeForceFX cards (5200, 5800 etc.) and all Radeon 9600, 9700, 9800, X400, X600, X800 cards. Intel GMA 950 and X3000 series.

Hardware with support for Shader model 3.0 shaders and limited support for floating point textures and framebuffer objects

  • Improved support for imaging pipeline and procedural textures due to higher precision and more complex shader programs.
  • Provide additional support for complex image processing operations, e.g., 2D convolution, local and neighborhood operations on images, thresholding and classification. (Shader model 3.0).
  • Advanced support for Vertex and Pixel shaders for 3D stimuli.
  • Support for floating point framebuffers and floating point blending operations, e.g., high dynamic range rendering and processing, precise execution of iterative image processing algorithms, computer vision and scientific stream computing algorithms.
  • This is what you minimally want if you need high bit precision color or luminance displays, e.g. in conjunction with devices like video attenuators, or Bits++ and similar high precision display devices.
  • Simple and fast creation of complex stimuli like procedural gabor patches, sine gratings, complex composited stimuli via alpha blending.
  • Remaining limitations: Stimuli are limited in precision to 16 bit floating point (effective 10-11 bits of linear precision) if you want to employ alpha-blending for stimulus creation. Drawing of high precision 32 bit floating point (effective 23 bits of linear precision) textures and offscreen windows is possible, but limited in speed.

Typical examples are all Radeon X1000 series GPUs (e.g., X1400, X1600, X1950) and all NVidia GeForce 6 and 7 series GPUs (e.g., GeForce 6800, GeForce 7800 etc.).

The Intel X3100 series chips and later (e.g., some Apple MacBooks) and its siblings are special in the sense that feature-wise they are Direct3D 10 cards with support for Shader model version 4 - they can do most of what the most recent state of the art cards of NVidia and ATI can do. However, they lack any support for frame-sequential stereo, anti-aliasing and high precision HDR framebuffers and due to lack of dedicated fast VRAM memory, they only have a low computational performance. So although theoretically “state of the art” cards, they are too restricted and weak for the typical applications of such state of the art cards.

State of the art hardware with support for Direct3D 10, ShaderModel 4.0 and fast full precision floating point textures and framebuffers

These cards remove the remaining limitations of the previous generation hardware mentioned above. They can store and handle stimuli (and any kind of drawing or image processing operations on that stimuli) at full speed without any restrictions at full 32 bit floating point precision, that is with at least 23 bits of effective linear precision. Shading operations, e.g., for post processing, or procedural drawing of complex stimuli can be even more complex.

This is the hardware you want for simple, efficient and fast generation of high precision contrast or color stimuli, complex compositing and post-processing of stimuli and for display on high precision devices like 10 bit framebuffers, 12/13 bit video attenuators or 14-16 bit devices like Bits++, or high dynamic range displays.

These graphics cards are also fully equipped for future GPU stream computing applications - They are capable of supporting some planned exciting future PTB features which wouldn’t be possible with previous generation GPUs.

Typical examples are all NVidia GPUs of type GeForce 8000 and later (e.g., 8200, 8400, 8600, 8800, 9200, 9600, 9800, GTX-2xx series and later) and all Radeon HD GPUs (HD 2000 / 3000 / 4000 series and later).

Choice of operating system and graphics card vendor

For most visual stimulation applications, choice of GPU vendor and operating system won’t be crucial. The different systems do however have some specific strength and weaknesses that may be important for some selected applications. This section summarizes a few of these considerations for different applications:

Relative strengths and weaknesses of Apple hardware + OS X

  • Choice of graphics hardware options for Apple hardware is rather limited and Apple exerts rather strong control over both hardware components and selection of features for the OS X OpenGL graphics system implementation. This allows Apple for good integration and performance tuning, as well as testing of the limited set of available graphics hardware with the available implementations of OS X. Our past experience is that this leads to rather high quality drivers with relatively few bugs and surprises (although they still have their fair share of bugs and we may have just been lucky so far) and a generally consistent feature set across different models of Apple hardware. Reliability of OS X graphics is high (compared to MS-Windows) and timing precision for visual stimulation with full screen displays (as typical for cognitive science experiments) is so far excellent.
  • Apple provides excellent graphics driver support for its mobile computers (MacBook, MacBook Pro), an area where users of Laptops under MS-Windows are accustomed to miserable vendor support and lots of pain.
  • One downside is higher costs for graphics hardware compared to plain PC hardware, as well as limited choice.
  • Apple most of the time doesn’t provide the most high-end GPUs as options, so if you’d need the last bit of performance you’d likely find better options for Windows or Linux on standard PC’s.
  • In some specialized areas, OS X graphics system lags behind the corresponding systems on Windows and Linux, sometimes by up to 1 or 2 years. In very few other areas it leads. Weak points of current OS X:

    • Dual display support is implemented in a much more inefficient way than on Windows or Linux. Therefore Psychtoolbox needs to work much harder “behind the scenes” to provide dual display stereo functionality, likely at a significant performance penalty when fast stimulus redraw and animation is needed for dual display stereo. For reasons beyond our understanding, displays on a dual display setup are not synchronized on OS X wrt. their video refresh cycles. This can cause severe flicker and tearing artifacts or limited synchrony in stimulus onset timing for dual display stereo stimulation, at least when NVidia GPUs are used. For selected ATI GPUs we provide a special workaround to solve this problem (type help PsychtoolboxKernelDriver in your local PTB installation for more information), but it would be much more admirable and pain free if Apple would take care of this problem. MS-Windows users can take well working and efficient dual display stereo stimulation for granted. In addition, OS X 10.5.3 to 10.5.6 have serious bugs in the drivers for NVidia GeForce 8000 hardware, which makes these setups unuseable for dual display fullscreen stereo!
    • In extension, OS X provides no support for genlock or framelock hardware, making reliable synchronization of more than two displays almost impossible. On Windows and Linux, a wide range of technical options exists for such special demands.
    • When drawing high precision stimuli (by use of floating point framebuffers), OS X has some low level technical limitations compared to MS-Windows and Linux: Again, Psychtoolbox implements some special workarounds to eliminate the problem for you, but again at a performance penalty in drawing.
    • Stimulus timing in windowed mode is unreliable to the point of being unuseable on OS X. This however is not a major limitation as experiment stimuli are usually not displayed in windowed mode.
  • A strong point of OS X is frame-sequential stereo presentation: This is supported on all ATI and NVidia GPUs under OS X out of the box. If you want similar functionality on Windows or Linux, you’ll need to buy expensive professional graphics cards like NVidia Quadro, or ATI FireGL / FirePro for the same functionality. The exception is OS X 10.5.6, which has serious bugs in the drivers for NVidia GeForce 8000 hardware, which makes these setups unuseable for frame-sequential stereo!

Relative strength and weakness of standard PC hardware under GNU/Linux and MS-Windows

In terms of graphics capabilities and support, Linux and Windows are usually on par with each other, due to the fact that the Windows and Linux graphics drivers are usually written by the same companies and therefore often share large amounts of internal code across these operating systems. Choice of graphics hardware is the same for Linux and Windows as well, as these operating systems run on the same set of PC hardware (including Apple Macintosh hardware). Therefore actual support for graphics features and graphics performance is no discriminating factor when choosing between Windows or Linux on PC hardware. There are other non-graphics related reasons to choose one OS over the other though.

Both systems provide generally feature rich, high performance, mostly reliable graphics drivers and GPUs. Both systems are strong in dual display support and for dual display stereo stimulation (compared to OS X shortcomings) and expensive for frame-sequential stereo stimulation (requiring high priced pro hardware, as opposed to OS X out of the box support on cheap hardware). Boths systems provide more advanced, faster support for high precision framebuffers than OS X. Both systems provide more options for special purpose hardware, e.g., genlocking / framelocking of many displays and support the latest GPU features ahead of OS X. This comes at the price of less consistency across different PC hardware configurations and more work/trouble for users in setting up and maintaining their graphics drivers. Driver support for Laptop GPUs under Linux often requires tinkering, but is plenty and good, once one gets used to it. Driver support for Laptop GPUs under Windows varies from vendor to vendor but is quite often a complete disaster.

Technically, in our experience, Linux is much more advanced, feature rich, robust and reliable in its operation than MS-Windows. It provides much more robust and precise timing behaviour, higher overall performance and it is much more flexible and customizable for applications with special needs. Unfortunately, most of our userbase consists of Windows users and the Linux userbase is very small. Therefore we can’t spend as many ressources on supporting and developing the Linux Psychtoolbox as we spend on maintaining the Windows Psychtoolbox for a larger userbase. This leads to the unfortunate situation that the Linux PTB lacks a few useful features wrt. the Windows Psychtoolbox, e.g., movie playback support, and that getting started with the Linux PTB likely involves a much steeper learning curve in the beginning. Therefore, we can not unconditionally recommend the current Linux Psychtoolbox over the Windows Psychtoolbox to beginners, but only to advanced power users, although this means that the majority of users will be locked to a technically far inferior operating system with many shortcomings.

Choice of ATI hardware vs. NVidia hardware

…to be written…

You could stop reading here and be reasonably well informed, but if you are really curious, feel free to continue reading about the nitty gritty technical details ;-)

Graphics hardware requirements for specific PTB features

OpenGL graphics hardware exposes its functionality via so called OpenGL extensions. Each extension defines a specific subset of functionality supported by the hardware. Specific advanced features of PTB-3 require your graphics hardware to support specific sets of OpenGL extensions. If you try to use an advanced PTB feature, PTB will probe your hardware for support of the required extension. If the extension is unsupported, PTB will either refuse use of an advanced feature or it will enable internal fallback implementations that do what you want, but at a much lower performance or precision and much higher resource requirements than if your hardware would support the extension. A list of all existing OpenGL extensions, including their full in-depth technical specification, can be found at the official OpenGL extension registry.

Different models of a specific generation of graphics hardware usually share support for a common set of extensions, but they differ in the precision, performance or efficiency with which features are supported as well as in the set of constraints that need to be fullfilled in order for the hardware efficiently to support a feature. The following websites list the specific set of extensions that are supported for specific models of graphics hardware for specific driver versions or operating system releases. They also list many interesting properties and limitations of these graphics cards. You will notice that there are separate websites for Windows/Linux and OS X and that if you compare the resource limits, capabilities and feature sets of the same models of graphics hardware between Win/Lin and OS X you’ll sometimes find significant differences. Given that the hardware is the same, these differences are imposed by the different design and implementation of the graphics drivers and OpenGL subsystems of Windows/Linux versus OS X.

If you want to buy a graphics card which is an optimal tradeoff between required features for your project and cost, you’ll have to match the listed requirements of PTB against the features in those databases. PTB’s Screen command outputs a list of all OpenGL extensions supported by your hardware + operating system + driver at startup (“OpenGL extensions are: …”) unless you suppress it. The websites above also provide a tool called GLInfo which probes your hardware and outputs a full listing of all tested properties if you need reliable information about your hardware.

Standard Screen subfunctions and their requirements

  • Support for fast, efficient textures and moderately fast Offscreen windows: GL_ARB_texture_rectangle or GL_EXT_texture_rectangle or GL_NV_texture_rectangle.

    • Everything on IntelMacs, everything on PowerMacs except ATI Rage, Rage 128 or Rage Pro. NVidia Geforce2 and later on Windows/Linux. Intel GMA 945.
  • Support for fast drawing of 3D geometry in MOGL: GL_EXT_draw_range_elements.

    • All OS X hardware. Most PC hardware.
  • Support for Screen('Flip', ..., clearmode) command with clearmode=1 (don’t clear after Flip): At least one AUX buffer for mono displays, two AUX buffers for stereo displays.

  • Well supported on OS X on PowerPC, faulty on OS X IntelMac, unsupported on most Windows and Linux systems, especially with ATI hardware. Alternatively if your hardware support the PTB imaging pipeline, you’ll get this feature very efficiently for free.

  • Support for different stereo display methods (stereomode flag in Screen('OpenWindow', ...):

    • Frame sequential stereo for shutter glasses: Blue line syncing method supported on all OS X hardware except ATI Rage and Intel chips. On Windows, only expensive professional line hardware is supported (ATI FireGL series and NVidia Quadro series). Linux can be extended in various ways to support commodity hardware in addition to the professional line hardware, and to support very special setups, e.g., high performance render clusters.

    • Vertical split screen stereo (modes 2 and 3): Supported on OS X PowerPC on all hardware. All other platforms need support for the PTB imaging pipeline for this to work.

    • Dualview stereo for free fusion, cross fusion, haploscopes and dual display systems: Works on all hardware and OS, either via cheap display splitter hardware like the Matrox DualHead2Go or via dual display (dual head) graphics cards.

    • Anaglyph stereo: Basic support (without automatic gain correction, desaturation or color to luminance conversion) works on all systems. Advanced anaglyph stereo with automatic color to luminance conversion, desaturation and gain correction is only supported on hardware that supports the PTB imaging pipeline.

  • Other algorithms: Need basic support for PTB imaging pipeline.

  • Support for full scene anti-aliasing (multisample parameter of Screen('OpenWindow', ...)): Needs GL_ARB_multisample with at least 1 multisample buffer (See constants Max Sample Buffers and Max Samples, bigger is better.

    • Supported on most ATI and NVidia hardware, not supported on Intel onboard graphics, e.g., GMA 950 of MacMini, IntelMac or MacBook.
  • Support for fast Offscreen windows: Needs support for basic imaging pipeline.
  • Support for fast geometric display distortion correction, display hotspotting correction, color correction, clut animation: Needs support for basic imaging pipeline.

Psychtoolbox imaging pipeline:

The Psychtoolbox imaging pipeline is a built-in framework for fast image processing on the graphics hardware, currently in beta stage. It allows to perform common image processing operations on image stimuli (represented as Psychtoolbox textures), to customize and extend the behavior of specific Screen drawing commands and to provide a set of fully automatic post processing operations on your final visual stimuli which may be useful for some more advanced applications. The infrastructure is integrated into PTB, but the specific operations are implemented as shader plugins, written in the OpenGL shading language (GLSL) and executed on the graphics processor itself. The imaging pipeline requires recent hardware for basic operation and mid-level to high-end hardware for the more advanced features.

Basic imaging pipeline support

Provides the following features:

  • Fast efficient support for Offscreen windows.
  • Fast support for “don’t clear after Flip” mode (dontclear=1) for the Screen('Flip') command, allows for incremental drawing of stimuli.
  • Automatic drawing of blue sync lines for frame sequential stereo on consumer hardware.
  • Fast support for vertical split screen stereo modes (stereomode 2 and 3).
  • Flexible high quality Anaglyph stereo modes with automatic conversion of color stimuli into grayscale images, online color gain correction, desaturation and alternate anaglyph implementations.
  • New stereo modes, e.g., interlaced stereo and vertically interlaced stereo for free viewing setups with lenticular lens systems.
  • Fast remapping of pixel values via lookup tables, e.g., for palette animation.
  • Geometric undistortion and alignment for non-rectilinear displays.
  • Correction of inhomogenities in display intensity via application of per pixel gain values. (On your request)

Minimum requirement for 2D drawing is the support for the following OpenGL extensions: GL_EXT_framebuffer_object, GL_ARB_multitexture, GL_ARB_shading_language_100, GL_ARB_shader_objects, GL_ARB_vertex_shader, GL_ARB_fragment_shader. The following cards and later models are known to fully support these extensions: ATI Radeon 9600, NVidia GeforceFX-5200, Intel GMA-950 onboard chip of Intel based MacMinis and MacBooks under OS X.

For 3D graphics via MOGL or OpenGL one needs these additional extensions: GL_ARB_depth_texture for depth buffer support and GL_EXT_packed_depth_stencil for stencil buffer support on some systems. Stencil buffers are unsupported on all PowerPC hardware (an OS limitation not a hardware limitation), unless you use OS X 10.5 “Leopard” and later.

High dynamic range support

This allows for drawing, processing and representation of images with floating point precision. Color values can exceed the normal 0-255 integer range of standard 8bpc framebuffers and one can handle images and colors with negative color components. This is useful for efficient creation of specific stimuli, e.g., fields of overlapping gabor patches and special blending operations. The final stimulus image can get automatically converted into a format suitable for special high precision display hardware, e.g., CRS Bits++, video attenuators, high dynamic range display devices.

Required extensions: A subset of GL_ARB_float_pixels, GL_APPLE_float_pixels, GL_ATI_float_pixels, GL_NV_float_pixels, GL_ATI_texture_float, GL_ARB_texture_float, GL_NV_texture_float.

At least the following graphics cards should support this according to their specification: NVidia Geforce-6000 series and ATI Radeon X800 series. The following cards have been successfully tested for support: ATI X1600 and NVidia Geforce 7800. All later cards will support this as well. The NVidia GeforceFX 5200 should support it, but malfunctioned on OS X PowerPC during tests. This may be different on OS X 10.5 Leopard, but is untested so far. The Intel chips do not support these functions.

Advanced support for imaging pipeline

This allows for more complex shaders and therefore for additional functionality, especially in the area of general purpose image processing:

  • Support for display devices with complex output processing requirements: e.g., BrightSide Technology High Dynamic Range display.
  • Support for 2D convolution, 2D FFT and other standard image processing operations.
  • Support for iterative algorithms and machine vision algorithms.

The graphics hardware needs to be Shader model 3.0 (aka DirectX 9.0c, aka Windows Vista Premium ready) compliant.

Known cards that should work well: (Follow the links for detailed infos about the different models)

Good luck in choosing a suitable card.