Video Out on the iMac

1998 – I’ve received a lot of feedback to The iMac: Not for Me. Several readers applauded my honesty in admitting that the iMac isn’t for everyone.

The iMac Supports an External Monitor and Higher Resolutions

But a lot more pointed out that the iMac can drive an external monitor and that the ATI Rage chips used in the iMac will drive resolutions to 1600 x 1200, although not with the internal monitor.

From MacInTouch (8 August):

To connect an external monitor to the iMac, you can connect it to the port that is located on the bottom side from the computer (after you remove the bottom cover – the one you remove to remove the motherboard). This port is a DB-15 Apple style and the internal monitor is connected there.

When you connect an external monitor, the ‘Monitor Resolution’ module from the control strip recognises a ‘VGA monitor’ and allows you to switch to any resolution.

This certainly makes the iMac a more viable engine for those of us used to larger (17-21″) monitors. The drawback is thta you have a beautiful iMac sitting there with a blank monitor.

I’ll bet someone could come up with a first class monitor switch to fit between the DB-15 connector, the connector for the internal monitor, and a connector for an external monitor. (You’d probably need to have the power off to make the switch, but that’s just a guess.)

With a switch like this, you have a fully functional, moderately portable iMac – but one you can attach to a larger screen when necessary.

Such a switch would also allow using the iMac with external displays, such as LCD projectors.

Don’t Forget the Mezzanine Slot

As noted on Mac News Today (August 19 and 20) and speculated here on July 17 (An Expansion Slot in iMac?), the iMac is not a closed system. There is a connector marked “mezzanine” on the motherboard, one that Apple says is “essentially a modified PCI slot….”

Although Apple asks that developers not create cards for the “Perch” slot, if it’s a modified PCI slot, there’s no reason someone couldn’t create an accelerated high resolution video card for the iMac.

This would give the iMac a feature that Mac users have grown accustomed to since the Mac II was introduced in 1987: multiple monitors.

With a mezzanine video card, the iMac would always drive its internal screen, but plugging in a second monitor would give the user a whole separate monitor to work on. With the Mac OS, it’s easy to set things up so you can drag windows from one screen to the other.

Two Possible Solutions

So there are two ways to address the iMac’s biggest shortcoming.

  1. Connect a larger external monitor to the DB-15 port inside the iMac, thereby disabling the internal screen. But with a well designed switch, it could be easy to toggle between the internal and external screens.
  2. Drop in a mezzanine video card, allowing full-time use of the internal 15″ iMac screen while permitting the easy addition of a second monitor as necessary.

As a personal preference, I don’t like the idea of owning an iMac and leaving its monitor blank – or having to open it to switch between the internal screen and an external one. A switch would be an elegant work around.

The best solution would be a separate video card with its own output in the mezzanine slot. Just add a well padded carrying case, and you’ve got the ultimate luggable computer.

Update: In October 1999, Apple introduced a new generation of iMacs that include a VGA port that mirrors what’s on the built-in display to an external monitor or video projector.