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Limitations of the 32-bit ABI
The 32-bit ABI was designed essentially for the R3000. We can't extend the 32-bit ABI to use new performance-related features and instructions of the R4400 and beyond. For example:
- We can't use 16 of the 32 floating point registers.
- We can't use any 64-bit arithmetic instructions.
- We can't use any 64-bit data movement instructions.
- We can't use any MIPS4/R8000 instructions.
Because of this, we lose the performance available from the chip. Floating point intensive programs are especially hurt by these limitations; indeed some are 50%-100% slower!
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