Low Pin Count

Low Pin Count

Low Pin Count
Year created	2002
Created by	Intel
Supersedes	Industry Standard Architecture
Superseded by	Enhanced Serial Peripheral Interface Bus (2016)
Width in bits	4
Speed	33 MHz
Style	Parallel
Hotplugging interface	no
External interface	no

The Low Pin Count bus, or LPC bus, is a computer bus used on IBM-compatible personal computers to connect low-bandwidth devices to the CPU, such as the boot ROM, "legacy" I/O devices (integrated into a super I/O chip), and Trusted Platform Module (TPM). "Legacy" I/O devices usually include serial and parallel ports, PS/2 keyboard, PS/2 mouse, and floppy disk controller.

Most PC motherboards with an LPC bus have either a Platform Controller Hub (PCH) or a southbridge chip, which acts as the host and controls the LPC bus. All other devices connected to the physical wires of the LPC bus are peripherals.

The LPC bus was introduced by Intel in 1998 as a software-compatible substitute for the Industry Standard Architecture (ISA) bus. It resembles ISA to software, although physically it is quite different. The ISA bus has a 16-bit data bus and a 24-bit address bus that can be used for both 16-bit I/O port addresses and 24-bit memory addresses; both run at speeds up to 8.33 MHz. The LPC bus uses a heavily multiplexed four-bit-wide bus operating at four times the clock speed (33.3 MHz) to transfer addresses and data with similar performance.

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