Personal Computer PCI Express System Bus

Personal Computer PCI Express System Bus PCI Express serial bus developed by Intel and its partners is intended to replace PCI parallel bus and its extended and specialised version - AGP. Despite similar names, PCI and PCI Express buses have little in common. Parallel data transfer protocol used in PCI limits the bandwidth and bus operation frequency; serial data transfer used in PCI Express ensures better scalability (specifications list the following PCI Express versions: 1x, 2x, 4x, 8x, 16x and 32x). PCI bus operates at 33 or 66 MHz frequency and provides bandwidth of 133 or 266 megabytes per second (Mbps), all of which, however, is shared by all PCI devices. PCI Express bus' operating frequency is 2.5 GHz, which ensures unidirectional bandwidth of 250 Mbps for each PCI Express 1х. To calculate bandwidth in case if several lines are available, one needs to multiply this 250 Mbps bandwidth by the number of lines and by 2, since PCI Express is a bidirectional bus. Usually, personal computers have 1 PCI Express 16x slot that makes video card installation possible and replaces AGP slot found in older PCs, and up to 4 PCI Express 1x slots. Mainboards used in servers and workstations can also be equipped with PCI Express 4x and 8x. One should not attempt to install a PCI Express board into PCI slot; and vice versa, PCI boards cannot be installed into PCI Express slots. Nonetheless, a PCI Express 1x board can be installed and will most likely properly function in PCI Express 8x or 16x slot, but not the other way round - a PCI Express 16x board simply won't fit into PCI Express 1x slot. In 2007, a new specification of PCI Express bus, 2.0, was adopted, whose main distinction is doubled bandwidth of each transfer line in each direction, which means an 8 Gbps bandwidth in each direction in case of the most popular PCI Express 16x version used in video cards. Intel X38 became the first chipset to support PCI-E 2.0. PCI-E 2.0 features full backward compatibility with PCI-E 1.0, i.e. all existing PCI-E 1.0 devices will operate normally in PCI-E 2.0 slots, and vice versa.

Видео Personal Computer PCI Express System Bus автора Школа Компьютерной Грамотности