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Difference between revisions of "V6/V8 Pixel Clock Issues"
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The first generation of VPro boards ([[V6]] & [[V8]]) have a design flaw that prohibits graphics modes in much of what might otherwise be considered the normal range for SGI desktop systems: | The first generation of VPro boards ([[V6]] & [[V8]]) have a design flaw that prohibits graphics modes in much of what might otherwise be considered the normal range for SGI desktop systems: | ||
* Modes in the 109-193MHz range cannot be selected at all on [[V6]]/[[V8]]. | * Modes in the 109-193MHz range cannot be selected at all on [[V6]]/[[V8]]. | ||
* Modes that are close to the lower end of that range (like 1280x1024_59/60) are only allowed at 8 bytes/pixel framebuffer size and even at that setting some people reported display problems (noise, flickering). | * Modes that are close to the lower end of that range (like 1280x1024_59/60) are only allowed at 8 bytes/pixel framebuffer size and even at that setting some people reported display problems (noise, flickering). | ||
− | + | This limits the ability of the V6 and V8 to use a number of common display resolutions, a situation that can be at least partially over come with the use of reduced blanking. As an example, a CVT-generated 1600x900@60Hz modeline without reduced blanking would have a Pixel Clock of 118.25MHz, which falls in the unusable 109-193MHz Pixel Clock range, while a modeline with reduced blanking would have a Pixel Clock of only 97.75MHz, which could be used by V6 or V8 graphics boards. | |
+ | == See Also == | ||
+ | * https://gainos.org/~elf/sgi/nekonomicon/forum/3/16725755/1.html | ||
[[Category:SGI]] | [[Category:SGI]] |
Latest revision as of 22:00, 30 July 2019
The first generation of VPro boards (V6 & V8) have a design flaw that prohibits graphics modes in much of what might otherwise be considered the normal range for SGI desktop systems:
- Modes in the 109-193MHz range cannot be selected at all on V6/V8.
- Modes that are close to the lower end of that range (like 1280x1024_59/60) are only allowed at 8 bytes/pixel framebuffer size and even at that setting some people reported display problems (noise, flickering).
This limits the ability of the V6 and V8 to use a number of common display resolutions, a situation that can be at least partially over come with the use of reduced blanking. As an example, a CVT-generated 1600x900@60Hz modeline without reduced blanking would have a Pixel Clock of 118.25MHz, which falls in the unusable 109-193MHz Pixel Clock range, while a modeline with reduced blanking would have a Pixel Clock of only 97.75MHz, which could be used by V6 or V8 graphics boards.