| Bit(s) | Name | Description |
|---|---|---|
| 15-13 | Reserved | |
| 12 | Reserved/Infinity Control (80387) | |
| 11-10 | RC | Rounding Control |
| 09-08 | PC | Precision Control |
| 07-06 | Reserved | |
| 05 | PM | Precision |
| 04 | UM | Underflow |
| 03 | OM | Overflow |
| 02 | ZM | Zero Divide |
| 01 | DM | Denormalized Operand |
| 00 | IM | Invalid Operation |
| Bit 09 | Bit 08 | Precision |
|---|---|---|
| 0 | 0 | 24 bits |
| 0 | 1 | Reserved |
| 1 | 0 | 53 bits |
| 1 | 1 | 64 bits |
| Bit 11 | Bit 10 | Function |
|---|---|---|
| 0 | 0 | To nearest even |
| 0 | 1 | Round down |
| 1 | 0 | Round up |
| 1 | 1 | Truncate |
See also: 8087/80287/80387 Status Word or go back