PowerMac G5 Quad GeForce 7800 GTX 512mb or Quadro 4500 FX

The ATI X1900 Mac Edition is more powerful than both of those cards.

Please educate yourself using the following link

http://en.wikipedia.org/wiki/Megahertz_myth

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https://discussions.apple.com/thread/3108418?start=0&tstart=0

The X1900 is slower than or equal to the 7800 GT in benchmarks:

http://barefeats.com/quad15.html

The 7800 GTX is faster than the 7800 GT in benchmarks:

http://www.barefeats.com/mutant4.html

The 7800 GTX has superior architecture, is capable of more triangles, more advanced shaders and outperforms other cards in most all applications.

Send me an email.

The 7800 GTX has superior architecture, is capable of more triangles, more advanced shaders and outperforms other cards in most all applications.

That is only your personal opinion. The X1900 is more powerful and efficient in every way than the 7800 series. Its only limitation is VRAM.

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Both the X1900 (R580) and the 7800 GTX (G70) are capable GPUs on advanced cards, both targeting and supporting Shader Model 3.0. 3D was a focal point in development for either card.

Approaches for shader implementation are very different between the two cards.

Arguements for either abound, but, 3D performance will be a defining factor to show shader prowess.

Architecturally, the cards are very different, but, in the end, memory bandwidth, an important performance feature, is highest with the 7800 GTX; 54.4 GB/s vs. 38 GB/s for the Mac Edition Radeon.

The next X19xx card, the X1950, almost doubled memory bandwidth over the X1900.

I know guys that use flashed X1950 (512 MB) cards really like them.

Support of DirectX 9 and Shader Model 3.0 make either card more than is necessary for OS X Core Image and OpenGL requirements.

You bring up a very important point regarding application specific performance.

Games are one form of benchmark, but not always indicative of real world performance.

In Photoshop, CS4, the 7800 GTX is a fully supported card, whereas the X1900 (256 MB) card is not supported. The 512 MB version of the X1900 is supported, but doesn't help owners of the Mac Edition.

There are pros and cons with either card, eventually driver and OpenGL support being the defining point.

Early driver issues with the X1900 in OS X and a relatively short retail availability likely affect the lack of empirical data on the cards performance.

The following, though comparing a X1900XT (not the little brother X1900GT which is the G5 version) with a Geforce 7800 GTX on platforms other than Mac, the comparisons do show pro oriented application performance.

Though not necessarily applicable to OS X and PPC Macs, I thought it to be an interesting set of tests.

http://ixbtlabs.com/articles2/cpu/nvidia-vs-ati-on-amd-and-intel.html

Either card is great, either is way better than the 6600, and, as you point out, availability is an important factor.

In Photoshop, CS4, the 7800 GTX is a fully supported card, whereas the X1900 (256 MB) card is not supported.

That is false information.