64-Bit Technology

 64-Bit Technology:Here, the 64-bit technology is relative to 32-bit. This number of digits indicates that the data width of cpu gprs (general-purpose registers, general-purpose registers) is 64-bit, 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.

To implement a true 64-bit computing, a 64-bit processor is not enough. A 64-bit operating system and 64-bit application software are required, without any of these elements, 64-bit computing cannot be implemented. For 64-bit processors, Intel and AMD both have released multiple series of 64-bit processors with multiple specifications. In terms of operating systems and application software, the current situation is not optimistic. Because Windows XP x64 is the only 64-bit operating system suitable for personal use, Windows XP x64 is also a transitional 64-bit operating system, after Windows Vista is released, it will be phased out, and Windows XP x64 itself is not perfect and easy to use. An obvious example is that drivers of various hardware devices are not complete, in addition, the 64-bit application software is basically not available. It is true that hardware and software vendors are reluctant to write drivers and applications for a transitional operating system. So if you want to implement a true 64-bit computing, you may have to wait until Windows Vista is popularized for a while.

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 technical X86-64:
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 in 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, 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.

 

Em64t technology and amd64 difference X86-64 (amd64/em64t ):
Designed to handle 64-bit integer operations at the same time, AMD is compatible with X86-32 architectures. It supports 64-bit logical addressing and provides the option of converting to 32-bit addressing. However, the default value of the data operation command is 32-bit and 8-bit, and the option of converting to 64-bit and 16-bit is provided; it supports general purpose registers. If it is a 32-bit operation, it is necessary to extend the result to a complete 64-bit operation. In this way, there is a difference between "direct execution" and "conversion execution" in the command. The command field is 8-bit or 32-bit, so that the field is too long.

X86-64 (amd64) generation is not a plug-in, x86 processor 32 bit addressing space limited in 4 GB memory, and the IA-64 processor is not compatible with x86. AMD fully consider the customer's needs, enhance the x86 Instruction Set function, so that this set of instruction sets can support 64-bit computing mode at the same time, So amd called their structure x86-64. In terms of technology, amd in the x86-64 architecture for 64-bit operation, amd introduced it to the new R8-R15 general register as the original x86 Processor register expansion, however, these registers are not fully used in a 32-bit environment. The original registers such as eax and EBX are also expanded from 32-bit to 64-bit. Eight new registers are added to the SSE unit to support sse2. Increasing the number of registers will improve the performance. At the same time, to support both 32-and 64-bit code and registers, the x86-64 architecture allows the processor to work in two modes: Long mode and legacy mode ), the long mode can be divided into 64bit mode and compatibility mode ). This standard has been introduced into the amd server processor opteron processor.

This year, the 64-bit em64t technology was also released, and before it was officially named em64t, it was ia32e. This is the name of Intel's 64-bit extended technology to differentiate x86 instruction sets. Intel's em64t supports 64-bit sub-mode, similar to AMD's X86-64 technology, with 64-bit linear plane addressing and 8 new general purpose registers (GPRS ), eight registers are added to support the SSE command. Similar to AMD, Intel's 64-bit technology will be compatible with ia32 and ia32e, and ia32e will be used only when the 64-bit operating system is running. Ia32e is composed of two sub-modes: 64-bit sub-mode and 32-bit sub-mode, which are backward compatible like amd64. Intel's em64t will be fully compatible with AMD's X86-64 technology. Now the Nocona processor has added some 64-bit technology, Intel's Pentium 4E processor also supports 64-bit technology.

Both are compatible with the 64-bit microprocessor architecture of the x86 instruction set, but em64t and amd64 are still different. The NX bit in the amd64 processor will not be provided in Intel's processor.