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Specs Textures 1T-SRAM Motherboard |
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The GameCube's GPU can use S3TC's compressed textures which provide for a 6:1 ratio in compression for 24-bit textures. For 16-bit textures the ratio is 4:1, and for 8-bit textures the ratio is 2:1. Let's consider how much compressed textures the GameCube can hold in its 24MB of main memory if we consider different memory size requirements for game/geometry/etc. |
| Code/Geometry/Etc
Free Texture Space
24-bit textures
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GameCube Playstation 2 Xbox Dreamcast Glossary |
6MB
18MB
108MB 8MB 16MB 96MB 10MB 14MB 84MB 12MB 12MB 72MB As you can see, the GameCube can store a lot of textures in it's memory using S3TC's texture compression format. Another benefit of using compressed textures is that the bandwidth requirements also decrease by the same ratio as the actual compression. At a ratio of 6:1, the memory bus can pass 6 times more textures. That means the GPU's |
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| texture cache bus of 10.4GB/sec can pass
62.4GB of 24-bit compressed textures, and the external bus of 2.6GB/sec
can 15.6GB of 24-bit compressed textures per second. If the developer chooses to use 16-bit textures over 24-bit textures to save space, lets compare: |
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| Texture Size 512x512
16-bit
24-bit |
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| Uncompressed
525KB
786KB |
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| Compressed
131KB
131KB |
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As you can see, the greater ratio is 6:1 for 24-bit textures, it makes more sense for the developer to use only 24-bit compressed textures as they are the same size as 16-bit compressed textures . S3TC also allows texture compression of transparencies, which the Vector Quantization (VQ) texture compression on the Dreamcast could not do. This will allow the GameCube to store a lot of transparencies in its main memory. Thanks to S3TC's texture compression, the GameCube's 1MB texture cache can hold the equivilant of 6MB of 24-bit textures. Thats roughly 8 x (512x512) 24-bit textures or 32 x (256 x 256) 24-bit textures for example. |
