This article originally appeared in TidBITS on 2005-11-07 at 12:00 p.m.
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Maxing Out Displays on the New Power Mac G5s

by Glenn Fleishman

When Apple released the new dual-core Power Mac G5 models, the company noted that a single Power Mac G5 can support eight displays. That can't be true, can it? After being blown away a few months ago when Apple sent Jeff Carlson two 30-inch Apple Cinema Displays for review (see photos at the two Flickr links below), we pictured a bright and no doubt high-temperature wall of the huge screens.

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If you upgrade the included GeForce 6600 to the $2,500 list price Quadro FX 4500 512 MB PCI Express card (a $1,600 upgrade at the Apple Store), you get two dual-link DVI adapters, which allows two 30-inch displays. The Power Mac G5 offers four PCI Express slots. Put a total of four Quadro FX's in and you can add... eight 30-inch displays. To get there, you'd need three more Quadro FX cards at $2,500 each, plus the single Quadro FX from the Apple Store (which limits you to one). Purchasing the cards, a Power Mac G5 Quad, and eight 30-inch displays would set you back a cool $32,500.

Can the Power Mac G5 really handle this? Unfortunately, no. Apple points out in a footnote, "Eight 20-inch or 23-inch Apple Cinema Displays can be connected to the Power Mac G5 using four NVIDIA GeForce 6600 graphics cards."

The issue is that the new PCI Express system has a specification known as "lanes," which is a measure of how much data the slot can carry. Each lane is about 250 megabytes per second (MBps). The Power Mac G5s have one 16-lane slot for graphics (4 GBps), one eight-lane slot (2 GBps) and two four-lane slots (1 GBps).

The GeForce 6600 can work with only four lanes, and so a Power Mac G5 can support four of those cards each with two smallish monitors (20- or 23-inch LCDs). The Quadro FX requires the full 16 lanes and two card slots.

How about 50? So I can't create an overwhelming video system in my office, but that doesn't mean others haven't tried... and succeeded. TidBITS stalwarts Joe Kissell and Dan Frakes both pointed me to HIPerWall, a project at the California Institute for Telecommunications and Technology. The HIPerWall (Highly Interactive Parallelized Display Wall) comprises 50 LCD panels for a total display surface of 23 by 9 feet (7.01 by 2.75 meters) and 200 million pixels. It's designed for earth sciences visualization, but will have biomedical and engineering applications, too. Twenty-five dual-2.7 GHz Power Mac G5s with 2 GB of RAM power two monitors each. They also have access to an aggregate of 10 TB of storage.


Based on the specs quoted for the HIPerWall system, I would guess that a second generation HIPerWall could use 13 Power Mac G5 Quads - each with 4 GB of RAM and powering four displays - to reduce the back-end footprint and lower costs slightly.