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HalfLucifer

Geforce2 MX has only 2 texture units?

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I use "glGetIntegerv(GL_MAX_TEXTURE_UNITS_ARB, &maxTexelUnits)" to get the maximum number of texture units and it turns out "2" ?! Only 2? I thought GF2MX has 4 texture units can be used! What''s wrong with that? Did I misunderstand something?

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No, I think it''s right. A Geforce 2 MX only habe two units. Not sure what''s about the third and forth generation, but I read something about that.

Ceya,
Phobeus

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The product specs at the NVIDIA site say it can do 4 simultaneous textures, but that doesn''t really mean we can actually use that.

Clipping planes for example use a texture unit on NVIDIA cards.


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crossposters, bah

it has 2, 4 texturelookups at a time, means 2 pixels processed at a time. but 2 textures.

nothing is different for programmers than a geforce 1 except speed and price. internally they changed a lot..

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Guest Anonymous Poster
GeForce 2 has 4 pixels rendering pipeline. It is not the same as 4 texture units. Actually it has only 2 tu''s. Only the latest grapics cards, like GeForce 3, ATI Radeon 8500 and some others, have 4 texture units.

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All GeForce cards (incl. GF2 MX/GTS/Pro/Ultra) but the GF3/4 have only 2 texture units. GF3+ has 4, so does the Kyro2. ATi Radeon 8500 has 6 texture units. Older ATi boards have 3.

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Guest Anonymous Poster
quote:
Original post by Yann L
All GeForce cards (incl. GF2 MX/GTS/Pro/Ultra) but the GF3/4 have only 2 texture units. GF3+ has 4, so does the Kyro2. ATi Radeon 8500 has 6 texture units. Older ATi boards have 3.


Actually, the GF3/4, and Radeon 8500 (maybe the Kyro as well) only have 2 physcal TMU''s, but they sort of "link" the pipelines so that it seems to have more.

If the Kyro2 really had 8 TMU''s, it would have MAD fillrate, but it doesn''t, because it''s only simulating that many TMU''s (which is done with multiple internal rendering passes).

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quote:

Actually, the GF3/4, and Radeon 8500 (maybe the Kyro as well) only have 2 physcal TMU''s, but they sort of "link" the pipelines so that it seems to have more


Well, I don''t know how it is done on chip-design level, and I don''t really care either. Fact is, that from OpenGL''s pov, the GF3/4 has 4 physical TUs. They are independently addressable (you have 4 independent s,t,r,q coordinates, 4 texture matrices, 4 regcom texture entry points, 4 simulateneous texture adressing operations, etc), and since fillrate is not affected if you activate more than 2 TUs, I highly doubt that they are double pumped. I''m practically sure, that the GF3+ has 4 physical TUs.

The Radeon has actually *3* physical TUs on board. I think they double-pump them to achieve the 6 units, so you have a fillrate loss, if you activate more than 3.

No idea about the Kyro, it returns 4 units, that''s all I know.

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