Due to the Integrated Visual Computing (IVC) architecture of the Visual Workstation, all the graphics resources are allocated out of the system resource pool. In order for the system resources to be available, they must be obtained from the system *before* the operating system has access to them. After all, you wouldn't want your screen's frame buffer to be swapped to disk, would you?
Therefore, it is very important to properly configure the Visual Workstation graphics and display settings for your application. Some of these settings have no direct affect on the applications, but make the system work better in general. Others can have a 10X impact on performance (either + or -), others perhaps +/- 10%. All these settings are contained on the "Display Properties" dialog of the NT Control Panel.
Since the Visual Workstation makes use of the IVC architecture , all the graphics memory needs are supplied from the total memory installed in the system. Thus, going from 32768 colors (which uses 2 bytes of memory per pixel) to TrueColor (which uses 4 bytes per pixel) doubles the amount of RAM used for the frame buffer. Likewise, enabling back buffer support doubles memory use again (a copy for the front buffer and a second copy for the back buffer). Increasing the screen resolution increases the memory use as well. So there is always a tradeoff in how much memory to allocate to the graphics and how much to allocate for the system. It is best to allocate as little as needed to the graphics to allow the hardware to support the application(s) needs. Otherwise, if the hardware can't support a given mode, a much slower software path will be used. For example, if the application request double-buffer graphics, but the hardware double-buffer support is disabled, the software rendering engine will provide a second buffer but speeds will be perhaps 1/20th that of the hardware path.
Conversely, allocating too much memory to graphics such that the application begins to page to disk, is not a good idea either. If no applications use texture mapping, then allocating memory for texture storage is a waste. If you are running multiple applications, then choose the graphics settings required by the most demanding application. The settings set an "upper limit" of capabilities that the hardware driver can provide. Setting capabilities too low, results in a much slower software path, setting too high wastes memory.
If you are faced with configuring a Visual Workstation for an unknown graphics application(s), then it is best to proceed in a logical, top-down manner to detemine the ideal setting in the shortest amount of time. The following steps will take you through the process:
If you plan to run multiple applications, perhaps with different graphics requirements, choose a setting that takes the maximum of the combined application's needs. For example if one app is happy with 32768 colors and the other needs TrueColor, use TrueColor. Likewise if one needs texture RAM and the other doesn't, allocate enough for the app that needs it. More resources is generally better unless it begins to take memory from the operating system which results in paging.
A word on rebooting: Often after changing settings, you'll be prompted to reboot your system for the changes to take affect, other times you will not. The underlying logic seems to be that a reboot is asked for when memory needs increase. For example going from 1024x768 to 1280x1024 resolution needs more memory, you must reboot to allocate it. Going down in resolution uses less memory, a reboot is not required, but the memory formerly used is not given back to the system until a reboot is done. When in doubt, the best bet it to reboot after changing settings. When I am investigating changes, I find if I max out the settings and reboot, then I can play with dropping individual settings down to see what impact they have without needing to reboot. Once I get the setting I want, I save it and reboot.
Here's some information on the inner workings of the system that I have assembled here for your convenience. All this information could be determined by using simple tools and visual inspection (which is how I did it).
The IVC workstations differ from typical PCs, in that they do not have a traditional BIOS ROM. Rather thay have an ARC PROM, which gives a much higher level of interface to boot level options, etc. Users of SGI MIPS workstations will immedeatly recognize the look and feel of the ARC PROM, because it has been used on most SGI MIPS workstations since the Indigo2.
command monitor" from the RunSystemUtilities screen:
OSLoad: NUMPROC=1option, will boot a multi-CPU system in a single-CPU mode.
OSLoad: MAXMEM=xxxMBwill restrict the system to "xxx" MB of RAM (currently this feature is broken).