8087/80287/80387 Control Word
| 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 |
Precision Control (Bits 08-09)
| Bit 09 |
Bit 08 |
Precision |
| 0 |
0 |
24 bits |
| 0 |
1 |
Reserved |
| 1 |
0 |
53 bits |
| 1 |
1 |
64 bits |
Rounding Control (Bits 10-11)
| 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