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Virtual Legacy Wires
Virtual legacy wires (VLW) are transactions over the Intel QuickPath Interconnect and Intel Ultra Path Interconnect interconnect fabrics that replace a particular set of physical legacy pins on Intel microprocessors. The legacy wires replaced include the INTR, A20M, and SMI legacy signals. See also * A20 line * INTR * System Management Mode References X86 architecture {{Computer-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intel QuickPath Interconnect
The Intel QuickPath Interconnect (QPI) is a point-to-point microprocessor, processor electrical connection, interconnect developed by Intel which replaced the front-side bus (FSB) in Xeon, Itanium, and certain desktop platforms starting in 2008. It increased the scalability and available bandwidth. Prior to the name's announcement, Intel referred to it as Common System Interface (CSI). Earlier incarnations were known as Yet Another Protocol (YAP) and YAP+. QPI 1.1 is a significantly revamped version introduced with Sandy Bridge-EP (Romley platform). QPI was replaced by Intel Ultra Path Interconnect (UPI) in Skylake (microarchitecture), Skylake-SP Xeon processors based on LGA 3647 socket. Background Although sometimes called a "bus", QPI is a point-to-point interconnect. It was designed to compete with HyperTransport that had been used by Advanced Micro Devices (AMD) since around 2003. Intel developed QPI at its Massachusetts Microprocessor Design Center (MMDC) by members of what ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Intel Ultra Path Interconnect
The Intel Ultra Path Interconnect (UPI) is a point-to-point processor interconnect developed by Intel which replaced the Intel QuickPath Interconnect (QPI) in Xeon Skylake-SP platforms starting in 2017. Interconnect UPI is a low-latency coherent interconnect for scalable multiprocessor systems with a shared address space. It uses a directory-based home snoop coherency protocol with a transfer speed of up to 10.4 GT/s. Supporting processors typically have two or three UPI links. Comparing to QPI, it improves power efficiency with a new low-power state, improves transfer efficiency with a new packetization format, and improves scalability with protocol layer that does not require preallocation of resources. UPI only supports directory-based coherency, unlike previous QPI processors which supported multiple snoop modes (no snoop, early snoop, home snoop, and directory). A combined caching and home agent (CHA) handles resolution of coherency across multiple processors, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
A20 Line
The A20, or address line 20, is one of the electrical lines that make up the system bus of an x86-based computer system. The A20 line in particular is used to transmit the 21st bit on the address bus. A microprocessor typically has a number of address lines equal to the base-two logarithm of the number of words in its physical address space. For example, a processor with 4 GB of byte-addressable physical space requires 32 lines (log2(4 GB) = 232), which are named A0 through A31. The lines are named after the zero-based number of the bit in the address that they are transmitting. The least significant bit is first and is therefore numbered bit 0 and signaled on line A0. A20 transmits bit 20 (the 21st bit) and becomes active once addresses reach 1 MB, or 220. Overview The Intel 8086, Intel 8088, and Intel 80186 processors had 20 address lines, numbered A0 to A19; with these, the processor can access 220 bytes, or 1 MB. Internal address registers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
System Management Mode
System Management Mode (SMM, sometimes called ring −2 in reference to protection rings) is an operating mode of x86 central processor units (CPUs) in which all normal execution, including the operating system, is suspended. An alternate software system which usually resides in the computer's firmware, or a hardware-assisted debugger, is then executed with high privileges. It was first released with the Intel 386SL. While initially special SL versions were required for SMM, Intel incorporated SMM in its mainline 486 and Pentium processors in 1993. AMD implemented Intel's SMM with the Am386 processors in 1991. It is available in all later microprocessors in the x86 architecture. Some ARM processors also include the Management Mode, for the system firmware (such as UEFI). Operation SMM is a special-purpose operating mode provided for handling system-wide functions like power management, system hardware control, or proprietary OEM designed code. It is intended for use onl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
