Specifications

CHAPTER 1
Overview of the AppleVision 1710AV and 1710 Displays
New Display Connections Specifications 15
All video cards had to know the sense codes of all displays connected. Once the sense
code was determined, the graphics driver trimmed its list of available timing modes to
those that it calculated were possible. Before System 7.1.2, and the introduction of the
Display Manager, all functional sResources not disabled by the PrimaryInit were always
shown in the Monitors control panel. There was no way to find out which timings had
been trimmed, and no way to tell which timing corresponded to a functional sResource.
When the Display Manager was introduced, Apple added two new video driver status
calls: cscGetConnection and cscGetModeTiming. These calls allow the Monitors
control panel to show only those modes that are marked as valid. The Monitors panel
does this by means of the DMCheckDisplayMode call, which in turn calls
cscGetConnection and cscGetModeTiming. Using this method, video cards can
have untrimmed functions sResources that correspond to invalid timing modes and do
not show up in the Monitors control panel.
You may view the sense code as returning the default timings supported by the display.
With Display Manager 2.0, smart displays, like the AppleVision 1710AV and 1710, can
enable and disable timings returned by the video driver. The video driver does not have
to know which timings are supported by a smart display, since the display itself makes
the finals decision as to whether it can support a particular timing.
DMCheckDisplayMode gets the video driver’s best estimate of the supported timings,
by means of the safe and valid bits; calls the smart display with this information; the
smart display looks at the timing constant returned by the cscGetModeTiming call,
and then modifies the valid and safe bits. The video driver is not notified of changes
made by the smart display.
Designing Cards and Drivers for a New Generation of Displays 1
The AppleVision 1710 displays are multiple-scan displays. As such, they would
normally use one of the three Type 6 Extended Sense Codes. However, these new 17-inch
displays support any possible resolution that falls within the timing range of 28-82 kHz
horizontal scan and 50-120 Hz vertical refresh. It is thus clear that the current Type 6
Extended Sense Codes are insufficient to cover all the possible variations of resolutions
supported by these new multiple-scan displays.
The AppleVision 1710 displays, therefore, rely on a new strategy, in which the Display
Manager, rather than the graphics driver, makes timing mode decisions. This strategy is
outlined in Designing PCI Cards and Drivers for Power Macintosh Computers. Refer to the
Chapter 11, “Graphics Drivers,” and the section “Display Timing Modes,” to see how
Apple is revising its strategy for timing modes.
Of particular importance in this new strategy is the requirement that the graphics driver
report, as available, all timing modes supported by the current graphics card hardware.
This allows the software shipped by the display manufacturer to report independently
the timing modes it supports, and allows the Display Manager to provide the point
where these two sets of timing modes intersect.
The AppleVision 1710 displays return the RGB 13” Type 6 (“straight 6”) sense code as a
safe choice when the display is connected to a Macintosh computer that does not have