3 ms·
It could definitely be clearer, but what makes you say the manual is misleading?
by moonchild 3y ago
It could definitely be clearer, but what makes you say the manual is misleading?
- jcranmer 3y agoThe two main things: * F0 and F2 are not mutually exclusive; there are few instructions that use both prefixes simultaneously. * It's a little bit more helpful, IMHO, to think of the prefixes not as prefixes but as extra bits to the opcode, so 0x66 0x00 and 0x00 are different instructions that just happen to both be ADD of different sizes. In general, the section on "legacy" prefixes seems to have largely been untouched since largely the 32-bit days, and so it's generally written as if it's mostly talking about 8086-style instructions whereas the actual implementation (especially when you start getting to the SSE instructions) has diverged somewhat from the original meanings of those prefixes, instead just stealing them for extra opcode bits.