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2004-04-13, 17:20:04
"What's the use of a pixelshader 3.0 Chip today?"

March, 31st 2004 / by Demirug / page 1 of 2

Contrary to nVidia, ATI has resolved as regards their new flagship, the R420 to do without a pixelshader 3.0. The effects of this decision are naturally limited predictable. As it will take some time until the official presentation of both adversaries, we want to bridge the time until the launches take place with a little mental tug and war on the effects of the technical (not
featurewise) differences between pixelshader 2.0 and 3.0.

As it is the case with every mental survey, things can finally turn out to be completely different as you thought. Therefore you should make no purchase decision blindfolded on the ground of such technical analyses, as best they could be suplementary to the taken tests with available hardware.

As with every new technique, disillusionment follows in the wake of enthusiam, that is evoked by techdemos. This mainly happens because realisation takes place in so far that the demonstrated techdemos at the launch will not be followed for some time by games featuring the same technique. Finally remains only the basic performance of the new card for the use of current or later published titels. Fitted with this knowledge from the past you may easily come to the conclusion, that the same will happen to the new Pixelshader 3.0 technology. The last
attempt of ATI to take a leading position with pixelshader 1.4 was not necessarely a big success. Thus the decision of ATI is comprehensable to do without Pixelshader 3.0 with regard to R420-chip. When a new technique is put to action in the long term, its definitly correct not
to spend ones money unthoughtfully for every new feature. But with every new technique its also a relevant problem of medium- or short term advantages. This creates a unusual situation with pixel shader 3.0: The ability, which is needed by the hardware to gain pixelshader3.0
compatibility, can be applied for the acceleration of techniques that go back to DirectX 7. Naturally in this process the driver plays an important role, as he has to adapt these older techniques (respectively the game code, that was written with it) for the optimal use of new
possibilities. The key to this acceleration is the ability of "dynamic branching". Up to now it always went like this, that for all pixels that belong to the same polygon also the same gradual procedures were carried out. But pixelshader 3.0 hardware makes it possible that for every
pixel different instructions can be executed with regard to the the situation. Hereby the number of procedures per pixel can be naturally different. The legitimate question now is, how such an ability should be able to accelerate the calculation of pixel effects, which have been developed without considering this very ability. The reason for this is simple: There have been already earlier situations, in which such an ability would have been useful. As it was not available, they had to ressort to a trick. They simply calculated the outcome of every possibility and then chose for each pixel the right one. When a driver recognises such a trick, which is incorporated (in the gamecode) he can change the pixel-calculation so that for each pixel only this possibility being calculated, that finally is also chosen for this very pixel. These tacts of calculation which would be applied for computing the unused alternatives, would have been spared.

2004-04-22, 22:14:33
Enjoy! (http://people.freenet.de/Alone/PS3.0II.rtf)

Der Rest folgt auch noch...

..und zwar hier. (http://people.freenet.de/Alone/PS3.0S.2.rtf)

2004-05-03, 12:00:29