The 64-bit processors on the market, including AMD athlon 64 and Intel's emt64 processors, both refer to the Bit Width of General registers rather than the bus. However, in terms of data bus, since 80386, it has already been 32bit, while CPU data buses above the Pentium level are all 64bit, including the 64-bit server processor, such as anteng. In general, 32-bit to 64-bit is usually used to distinguish the Bit Width of General registers. There is also a more specific saying: the 64-bit technology here is relative to 32-bit, which refers to the general-purpose registers (general-purpose registers) the data width is 64-bit, And the 64-bit instruction set is the command to run 64-bit data, that is, the processor can run 64-bit data at a time. 64-bit processors are not available now. 64-bit processors have been available for a long time in high-end CPU (Reduced Instruction Set computers, for example, sun's ultrasparc III, IBM's power5, and HP's Alpha. 64bit computing has two main advantages: it can perform integer operations in a larger range; it can support larger memory. We cannot simply think that 64-bit processor performance is twice the performance of 32-bit processor because of Digital changes. In fact, in 32-bit applications, the performance of 32-bit processors is even stronger. Even 64-bit processors have higher performance in 32-bit applications. Therefore, we need to recognize the advantages of the 64-bit processor, but do not believe that 64bit. Currently, the 64-bit CPU technology mainly includes amd amd64-bit technology, Intel em64t technology, and Intel IA-64 technology. Among them, IA-64 is independently developed by Intel, not compatible with the current traditional 32-bit computer, only for itanium (anteng) and subsequent products itanium 2, general users will not involve, therefore, we will only give a brief introduction to amd64-Bit Technology and Intel's em64t technology. Amd64-Bit Technology amd64-bit technology is added to the original 32-bit x86 Instruction Set Based on the X86-64 extended 64-bit x86 instruction set, so that the chip is compatible with the original 32-bit x86 software on the hardware, it also supports 64-bit X86-64 extension, making this chip a real 64-bit x86 chip. This is a true 64-bit standard with a X86-64 capable of 64-bit addressing. Several new sets of CPU registers added to the X86-64 provide faster execution efficiency. Registers are used internally by the CPU to create and store the CPU operation results and other operation results. The Standard 32-bit X86 architecture includes eight General registers (GPR), and AMD adds eight more groups (X86-64) in the R8-R9 to increase the number of registers to 16 groups. X86-64 registers default bit 64-bit. Also added 8 128-bit XMM registers (also called SSE registers, XMM8-XMM15), which will provide more space for single-instruction multi-data stream technology (SIMD) operations, these 128-bit registers provide 128-bit dual-precision processing in vector and scalar computing mode, providing hardware basis for 3D modeling, vector analysis, and VR implementation. By providing more registers, CPUs produced according to X86-64 standards can process data more effectively and transmit more information in a clock cycle. Em64t technology intel officially defines em64t as follows: em64t stands for extended memory 64 technology, that is, extended 64 bit memory technology. Em64t is an extension of the Intel IA-32 architecture, namely, IA-32e (Intel Architectur-32 extension ). With the em64t technology attached, the IA-32 processor allows software to take advantage of more memory address space while being compatible with IA-32 software, and allows the software to write 32 bit linear addresses. Em64t especially emphasizes the compatibility between 32 bit and 64 bit. Intel added 8 64-bit GPRS (R8-R15) for the new core, and expanded all the original GRPS to 64-bit, as described above, which can improve the integer computing capability. 8 128bit SSE registers (XMM8-XMM15) were added to enhance multimedia performance, including support for SSE, sse2, and sse3. Intel designed two models for processors supporting em64t technology: Legacy IA-32 mode and IA-32 mode ). In a processor supporting em64t technology, there is a part called extended feature enable register, ia32_efer. bit10 controls whether em64t is activated. Bit10 is called IA-32e mode active or long mode active ). When LMA = 0, the processor runs in the traditional IA-32 mode as a standard 32-bit (ia32) processor; When LMA = 1, em64t is activated, the processor runs in IA-32e extended mode. Currently, amd supports 64-bit CPU, including the athlon 64 series, athlon FX series, and opteron series. Intel's 64-bit CPU supports the Nocona core Xeon series, the Pentium 4 6 series using the Prescott 2 m core, and the P4 EE series using the Prescott 2 m core.