Filter
Top Products
2–2 Alpha Architecture Handbook
Figure 2–2: Word Format
A word is specified by its address, the address of the byte containing bit 0.
A word is a 16-bit value. The word is only supported in Alpha by the load, store, sign-extend,
extract, mask, and insert instructions.
2.2.3 Longword
A longword is 4 contiguous bytes starting on an arbitrary byte boundary. The bits are num-
bered from right to left, 0 through 31, as shown in Figure 2–3.
Figure 2–3: Longword Format
A longword is specified by its address A, the address of the byte containing bit 0. A longword
is a 32-bit value.
When interpreted arithmetically, a longword is a two’s-complement integer with bits of
increasing significance from 0 through 30. Bit 31 is the sign bit. The longword is only sup-
ported in Alpha by sign-extended load and store instructions and by longword arithmetic
instructions.
Note:
Alpha implementations will impose a significant performance penalty when accessing
longword operands that are not naturally aligned. (A naturally aligned longword has zero
as the low-order two bits of its address.)
2.2.4 Quadword
A quadword is 8 contiguous bytes starting on an arbitrary byte boundary. The bits are num-
bered from right to left, 0 through 63, as shown in Figure 2–4.
Figure 2–4: Quadword Format
015
:A
031
:A
63
0
:A