Comparison of Octane MXE to Deskside Onyx2

In general, if you're faced with this choice, I would say go with Onyx2, ie. if you're considering the very top end of an Octane's current capabilities, then there is a danger that you will have no room to grow your computational resources should project requirements exceed original expectations - a common occurence I expect. Think of this as rather like buying a hifi speaker system: if one finds oneself contemplating the very top-end of a particular model's capabilities, then one should get the next model up that can handle the task easily, rather than at the peak of its capabilities.

This page gives some detailed examples of why Onyx2 is the better choice when faced with such a decision in the world of 3D real-time graphics, especially VR. Obviously, there may be budget limitations which leave one with no choice, but my comments here are targeted more at customers who tend to have higher budgets: aerospace, automotive, government, medical, oil industry, etc. Such industries would prefer to go with cheaper systems whenever possible, but they're much more likely to select a faster system if they believe there is sufficient justification for their purchase or lease. When it comes to what I call 'industrial' quality projects, it is unlikely that managers would be so short-sighted as to limit the scope of a research program by under-equipping the research team. The team's focus should be on the problem, not on getting round the limitations of their equipment.

Many of the comments I give below are based on an email I received from someone working on an automotive VR research project who had exactly the above conumdrum to solve. First some summary tables to convey the basic differences between Octane-MXE and low-end Onyx2 as they are right now (this data is extracted from my SGI Graphics Performance Comparison Tables page; see that page for a 'key', eg. 'R' = Reality, as in Onyx2 Reality):

                           3D        Flat     Lit GZ    Lit        Lit  
                    X      Depth     Tri      Tri/sec   Tex        GZ   
                  Lines    Cued GZ   Strips             GZ         Indep
                           Lines     No Z               Tri/sec    Quads

Octane MXE:       3.88M    2.29M     ?        2.19M     1.42M      880K 
Onyx2 R:          ?        ?         ?        ?         5.5M       ?
Onyx2 IR (9):     ?        ?         ?        ?         11.0M      ?
Onyx2 IR2 (9):    ?        ?         ?        ?         13.1M      ?


                  GF        Tex GFZ   Conv(3x3)   Conv(5x5)   Color
                  Pix/sec   pix/sec                           Lookups/sec

Octane MXE:       240M      138M      33.7M       27.12M      96.4M
Onyx2 Reality:    448M      188M      ?           30M         ?
Onyx2 IR (9):     896M      624M      ?           60M         ?
Onyx2 IR2 (9):    896M      768M      ?           60M         ?


                  Data       CDRS       Design     Advanced      Lightscape
                  Explorer              Review     Visualiser

OCT MXE/250:      18.37      55.46      10.62      20.09         1.55
Onyx2 R/180:      21.72      91.54      15.83      23.70         2.41
Onyx2 R/195:      21.90      92.72      16.27      23.84         2.61
Onyx2 IR/195:     35.65      161.29     20.82      45.43         2.65
Onyx2 IR/250:     41.60      ?          23.96      ?             3.30


                  Characters    Screen     Max Framebuffer    3D Vectors
                  Per Second    Clear      Memory Size        Per Second


Octane MXE:       ?             ?          27MB               ?
Onyx2 R:          ?             ?          80MB               ?
Onyx2 IR:         ?             ?          320MB              ?

• The appearance of the new SGI NT Visual Workstation,

• The doubtless approach of new graphics options for Octane and Onyx2 (processors too),

• People who need something as powerful as Onyx2 Reality almost certainly actually need something more like InfiniteReality, ie. in terms of what one can be given for the cost of a high-end Octane compared to the cost of a low-end Onyx2, there is an inbetween zone of performance which customers rarely consider. In other words, if I'm happy with MXE's 1.5M triangles/sec, then fine. If not, then I'd rather have 10M/sec than 5M/sec (ie. the added cost of moving to Onyx2 and having Reality graphics isn't worth just a 3.5X increase in performance - better to go for a larger performance increase if there to be added cost).

  
  

Please don't ask me when new products will be released as I honestly have no idea. One can merely judge from common sense that Octane's current graphics technology, which is based the IMPACT technology from the old Indigo2 days, is showing its age, while InfiniteReality in its basic form is more than 2 years old now. With the release of the Visual Workstation, I find it highly unlikely that the current options for Octane and Onyx2 would be left alone for much more than a month or two.

So, why is Onyx2 better than Octane for VR projects, etc.? Here are some reasons:

• Greater main processing power (ie. larger number of processors).

  Having a fast graphics system is no use if there is insufficient main CPU power to handle application overhead. Plus, complex projects may, for example, require setups such as 3 or more simultaneous video outputs; for efficient processing and reliable performance, it is common to organise such projects by allocating different CPUs for distinct tasks. Exactly what is appropriate depends on the specifics of the application.

  It is not possible to get the most out of a graphics system like InfiniteReality without having good main CPU power, and that means - for tough problems - at least 4 CPUs. My SGI General Performance Comparisons page has some examples where the speed of an Onyx2 InfiniteReality is limited by the speed of the main CPU rather than the graphics system.

• VR projects often need multiple display outputs, perhaps because one requires more than one person immersed in the 3D environment, or because one needs an instructor display as well as a VR output, or both. Octane could handle two displays, but the person who contacted me wanted three 1280x1024 VR displays and probably an instructor station too.

  
  

1. One needs lots of frame buffer video memory to support the multiple outputs.

2. If one require high-quality full-scene multispatial anti-aliasing (definitely needed for good quality VR), then lots of video memory is required (8 times the normal amount).

3. In order to sustain high frame rates at high-resolution, one needs high pixel fill rates. This is why something like an Intergaph Wildcat is useless for VR applications: 90M textured pixels/second is nowhere near enough to handle complex scenes at 1280x1024 60fps. Besides, Wildcat does not offer quad-buffered 48bit RGBA anyway. InfiniteReality offers 800M pixels/second, as well as features such as dynamic resolution rendering to ensure consistent update rates.

   For VR work, high frame rates are critical; those involved with video conferencing technologies have found a negative effect if the frame rate of a video link is too low - in the same way, a VR display will not be able to offer good insight into solving a problem if the display update rate is low (the level of interaction and cognitive would be insufficient to gain any further understanding of the problem).

4. If there are to be multiple viewpoints, then that will require multiple preprocessing for the graphics pipe, ie. being able to assign 1 CPU per viewpoint ensures efficient usage of available host compute power.

In the above example, where at least 3 displays are required (more likely 4 since an instructor display is also usually needed), again Onyx2 is the choice since an option card offers up to 8 display outputs whereas I believe Octane is limited to 2.

I know of a researcher at a medical institution in Alaska who was organising an upgrade to their SGI system. They were considering an Onyx2 Reality as an upgrade over their old IRIS Crimson. After some consideration and demonstrations, they eventually chose InfiniteReality instead (2X faster than Reality). A wise move.

Final notes:

• Definitely get 64MB texture memory if you purchase or lease a system like Onyx2 IR - what is the point of obtaining such high quality equipment if that equipment is under-resourced and thus unable to offer the best of its abilities?

• Anyone considering purchasing high-end image generation hardware should always ask for a hands-on demonstration by their local SGI sales representative; never buy any computer hardware until you've tested a target system and are sure it meets your needs - what if even IR isn't fast enough and it turns out you need multiple IR graphics pipes?

Your focus should be on solving the problem, whatever that may be: research program, specific task, etc. Don't obtain a system that can't help you solve your problem.