9-6
PROGRAMMING WITH THE STREAMING SIMD EXTENSIONS
When storing real values in memory, single-real values are stored in 4 consecutive bytes in
memory. The 128-bit access mode is used for 128-bit memory accesses, 128-bit transfers
between SIMD floating-point registers, and all logical, unpack and arithmetic instructions. The
32-bit access mode is used for 32-bit memory access, 32-bit transfers between SIMD floating-
point registers, and all arithmetic instructions.
Table 9-2. Real Number and NaN Encodings
NOTES:
1.Integer bit is implied and not stored for single-real and double-real formats.
2.The fraction for SNaN encodings must be non-zero.
Class
SignBiased Exponent
Significand
Integer
1
Fraction
Positive+
?
0
11..11
1
00..00
+Normals
0
.
.
0
11..10
.
.
00..01
1
.
.
1
11..11
.
.
00..00
+Denormals
0
.
.
0
00..00
.
.
00..00
0
.
.
0
11.11
.
.
00..01
+Zero
0
00..00
0
00..00
Negative
?
Zero
1
00..00
0
00..00
?
Denormals
1
.
.
1
00..00
.
.
00..00
0
.
.
0
00..01
.
.
11..11
?
Normals
1
.
.
1
00..01
.
.
11..10
1
.
.
1
00..00
.
.
11..11
-
?
1
11..11
1
00..00
NaNs
SNaN
X
11..11
1
0X..XX
2
QNaN
X
11..11
1
1X..XX
Real Indefinite
(QNaN)
1
11..11
1
10..00
Single
¬
8 Bits
?
>
¬
23 Bits
?
>
