The Intel486 processor (and newer processors since) guarantees：
- Reading or writing a byte
- Reading or writing a word aligned on a 16-bit boundary
- Reading or writing a doubleword aligned on a 32-bit boundary

The Pentium processor (and newer processors since) guarantees：
- Reading or writing a quadword aligned on a 64-bit boundary
- 16-bit accesses to uncached memory locations that fit within a 32-bit data bus

The P6 family processors (and newer processors since) guarantee：
- Unaligned 16-, 32-, and 64-bit accesses to cached memory that fit within a cache line

とのことなので「The Pentium processor (and newer processors since) 」ならおk