The DVI Output on the MacBook Pro

SpreadTooThin wrote:

> The DVI connector for external displays looks like a DUAL Link
> Digital / Analog connector.

All Macs with built-in DVI connector that I've seen have the full DVI-I
dual-link connector (3x8 digital grid, plus the four pins for analog).

I assume the full connector is used in all cases for maximum
compatibility with connectors. If cables have all pins, they won't plug
into a single-link connector (which has two columns missing in the
middle of the digital grid).

> Why DUAL? If there are two separate output channels are they
> different or the same or is one of them not connected.
> Can I connect two external displays?

The difference between single and dual link is the amount of data which
can be sent to a digital display. It doesn't mean you can connect two
monitors. Dual link has twice as many pins for sending data to the
monitor, so twice as much data can be sent in the same amount of time.
It only applies to digital connections: analog is a separate issue.

Not all Mac models with DVI support dual link, even though the connector
has all the pins. No model with Mini-DVI supports dual link, as far as I
know.

In general, older Macs or those with less video RAM are limited to
single link displays. Newer Macs or those with more video RAM can
support a dual-link display.

In Apple's range of monitors, the 30 inch Cinema Display requires
dual-link, but the others will work on single-link.

The "dual link" cannot be separated to drive two independent displays in
a simple way. There are apparently hardware products which can support
this, by acting as a larger screen as far as the computer is concerned,
then splitting and buffering the DVI signal to connect two smaller
screens.

The two links that form the dual link share many signals, including the
ones used to identify the monitor. These signals are also shared with an
analog monitor, so you can't mix digital and analog either (without
external hardware which split and buffered the digital signal and did
its own digital to analog conversion).

--
David Empson
dempson.DeleteThis@actrix.gen.nz