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FMULT (Super FX): Difference between revisions
From SnesLab
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# Official Nintendo documentation on FMULT: 9.33 on [https://archive.org/details/SNESDevManual/book2/page/n202 Page 2-9-46 of Book II] | # Official Nintendo documentation on FMULT: 9.33 on [https://archive.org/details/SNESDevManual/book2/page/n202 Page 2-9-46 of Book II] | ||
# example: [https://archive.org/details/SNESDevManual/book2/page/n203 page 2-9-47], lbid. | # example: [https://archive.org/details/SNESDevManual/book2/page/n203 page 2-9-47], lbid. | ||
# [https://archive.org/details/SNESDevManual/book2/page/n155 page 2-8-16], lbid. | # 8.2 "Multiplication Instructions" on [https://archive.org/details/SNESDevManual/book2/page/n155 page 2-8-16], lbid. | ||
Revision as of 16:18, 2 July 2024
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Opcode | Length | ROM Speed | RAM Speed | Cache Speed | |||
| 9F | 1 byte | 7 or 11 cycles | 7 or 11 cycles | 4 or 8 cycle | |||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| B | ALT1 | ALT2 | O/V | S | CY | Z | ||
| 0 | 0 | 0 | . | |||||
FMULT is a Super FX instruction that performs a signed multiplication. The two factors are the source register and R6. The upper 16 bits of the 32-bit product are stored in the destination register. Bit 15 of the product is stored in CY. The lower 15 bits of the product appear to be discarded.
The exact speed depends on the state of the CFGR register. FMULT utilizes the 8-bit multiplier four times.[3]
R4 cannot serve as the destination register, but any other register from R0 to R15 can. If R4 is specified as the destination register anyway, the product will simply not be written to it and will be lost instead.[3]
FMULT shares its multiplication circuit with LMULT.
See Also
External Links
- Official Nintendo documentation on FMULT: 9.33 on Page 2-9-46 of Book II
- example: page 2-9-47, lbid.
- 8.2 "Multiplication Instructions" on page 2-8-16, lbid.