The ATI Radeon 9800 XT will not run a 30" display at full resolution. See:
<http://support.apple.com/specs/powermac/Power
Mac_G5_Late2004.html>
"Graphics and displays
AGP 8X Pro graphics slot supporting up to 2 GBps data throughput, with one of the following graphics cards installed:
NVIDIA GeForce FX 5200 Ultra with 64MB of DDR SDRAM, DVI and ADC ports
ATI Radeon 9600 XT with 128MB of DDR SDRAM, DVI and ADC ports
ATI Radeon 9800 XT with 256MB of DDR SDRAM, DVI and ADC ports (build-to-order option; occupies AGP slot and adjacent PCI slot)
NVIDIA GeForce 6800 GT DDL with 256MB GDDR3 SDRAM, two dual-link DVI ports (occupies AGP slot and adjacent PCI slot)
NVIDIA GeForce 6800 Ultra DDL with 256MB GDDR3 SDRAM, two dual-link DVI ports (build-to-order option; occupies AGP slot and adjacent PCI slot)
Built-in support for digital resolutions up to 1920 x 1200 pixels. The NVIDIA GeForce 6800 Ultra DDL or NVIDIA GeForce 6800 GT DDL graphics card is required to power the 2560 x 1600-pixel resolution of the 30-inch Apple Cinema HD Displays."
You need a graphics board with dual-link DVI to run the 30" at full resolution. The AGP cards Apple sold that have dual-link DVI ports are:
ATI Radeon 9650 XT (one single-link, one dual-link DVI)
NVIDIA GeForce 6800 GT DDL (two dual-link DVI)
NVIDIA GeForce 6800 Ultra DDL (two dual-link DVI)
Apple doesn't sell these as retail items, but might sell them as replacement parts, or you could look for them used. Be sure to get Mac versions.
There are two new graphics boards that will work:
ATI Radeon® X800 XT MAC Edition RoHS 256MB AGP (one ADC, one dual-link DVI)
<http://shop.ati.com/product.asp?sku=3170810>
ATI Radeon® 9600 Pro PC & MAC Edition RoHS 256MB AGP (one single-link, one dual-link DVI)
<http://shop.ati.com/product.asp?sku=3170809>
These cards mat be available at
<http://eshop.macsales.com/shop/video/hardware/>
