Intel 64 and IA-32 Architectures Software Developers Manual Volume 3B, System Programming Guide Part 2

Table Of Contents
Vol. 3 B-15
MODEL-SPECIFIC REGISTERS (MSRS)
If the SSE3 feature flag
ECX[0] is not set
(CPUID.01H:ECX[bit 0] = 0),
the OS must not attempt to
alter this bit. BIOS must
leave it in the default state.
Writing this bit when the
SSE3 feature flag is set to 0
may generate a #GP
exception.
21:19
22 Limit CPUID Maxval. (R/W)
When this bit is set to 1,
CPUID.00H returns a
maximum value in EAX[7:0]
of 3.
BIOS should contain a setup
question that allows users
to specify when the installed
OS does not support CPUID
functions greater than 3.
Before setting this bit, BIOS
must execute the CPUID.0H
and examine the maximum
value returned in EAX[7:0]. If
the maximum value is
greater than 3, the bit is
supported.
Otherwise, the bit is not
supported. Writing to this
bit when the maximum value
is greater than 3 may
generate a #GP exception.
Setting this bit may cause
unexpected behavior in
software that depends on
the availability of CPUID
leaves greater than 3.
0F_03H
Table B-2. IA-32 Architectural MSRs (Contd.)
Register Address Architectural MSR Name
and bit fields
(Former MSR Name) MSR/Bit Description
Introduced as
Architectural
MSR
Hex Decimal