Volume 3: General-Purpose and System Instructions - Stanford ...

24594 Rev. 3.10 February 2005 AMD64 TechnologyTable 3-7.CPUID AMD Feature Support (Extended Function 8000_0001h—EDX) (continued)EDXBit26 Reserved.Feature(feature is supported if bit is set to 1)Same asFunction 1(Table 3-5) 127 RDTSCP Instruction. no28 Reserved.29 Long Mode. See “Long Mode” in Volume 2. no3031AMD Extensions to 3DNow! Instructions. Indicates support for the AMD extensions tothe floating-point (3DNow!) 64-bit media instructions. For details, see Appendix D,“Instruction Subsets and CPUID Feature Sets.”AMD 3DNow! Instructions. Indicates support for the floating-point (3DNow!) 64-bitmedia instructions. For details, see Appendix D, “Instruction Subsets and CPUID FeatureSets.”nonoNote:1. If a bit has the same meaning for function 1 as it does for function 8000_0001h, the processor sets or clears the bit identicallyfor both functions.Extended Functions8000_0002h–8000_0004h:Processor NameExtended functions 8000_0002h, 8000_0003h, and 8000_0004h together return anASCII string containing the name of the processor implementation. Software cansimply call these three functions in numerical order to obtain a 48-character ASCIIname string. Although the name string can be up to 48 characters in length, shorternames have unused byte locations filled with the ASCII null character (00h).Note: The BIOS must program the name string before these functions are executed;otherwise, these functions return the default processor name string (48 ASCIInull characters).The name string returned by these functions is in little-endian format. Extendedfunction 8000_0002h returns the first 16 characters of the name and extendedfunction 8000_0004h returns the last 16 characters. For each of the three groups of 16characters, the functions return the name (in order of least-significant to mostsignificantbyte) in the EAX, EBX, ECX, and EDX registers. The first character residesin the least-significant byte of EAX, and the last character resides in the mostsignificantbyte of EDX.CPUID 129