{"id":272,"date":"2020-08-18T19:23:47","date_gmt":"2020-08-18T20:23:47","guid":{"rendered":"http:\/\/www.linux-tutorial.info\/?page_id=77"},"modified":"2020-08-22T19:26:17","modified_gmt":"2020-08-22T20:26:17","slug":"this-is-the-page-title-toplevel-107","status":"publish","type":"page","link":"http:\/\/www.linux-tutorial.info\/?page_id=272","title":{"rendered":"PCI"},"content":{"rendered":"\nPCI<\/title>\n<p>\nMore and more machines you find on the market today are being built only with some form of\n<glossary>PCI<\/glossary> local buses. One\nadvantage that <glossary>PCI<\/glossary>\noffers over VL-Bus is the higher performance, automatic configuration of\nperipheral cards, and superior compatibility. A major drawback with the other\n<glossary>bus<\/glossary> types (ISA, <glossary>EISA<\/glossary>,\n<glossary>MCA<\/glossary>) is the <glossary>I\/O<\/glossary>\n<glossary>bottleneck<\/glossary>.\nLocal buses overcome this by accessing memory using the same signals\nlines as the <glossary>CPU<\/glossary>.\nAs a result, they can operate at the full speed of the CPU as well as utilizing\nthe 32-bit data path. Therefore, <glossary>I\/O<\/glossary>\nperformance is limited by the card and not the <glossary>bus<\/glossary>.\n<\/p>\n<question id=\"247\" text=\"PCI referred to as a 'mezzanine bus' as it sits between the system and expansion buses.\" \/>\n<question id=\"248\" text=\"How many devices can PCI support?\" \/>\n<p>\nAlthough\nPCI is referred to as a local <glossary>bus<\/glossary>,\nit actually lies somewhere “above” the system bus. As a result it\nis often referred to as a “mezzanine <glossary>bus<\/glossary>”\nand has electronic “bridges” between the system bus and\nthe expansion <glossary>bus<\/glossary>.\nAs a result, the <glossary>PCI<\/glossary>\nbus can support up to 5 PCI devices, whereas the VL-BUS can\nonly support two or three. In addition, the <glossary>PCI<\/glossary>\n<glossary>bus<\/glossary>\ncan reach transfer speeds four times that of\nEISA or <glossary>MCA<\/glossary>.\n<p>\nDespite <glossary>PCI<\/glossary>\nbeing called a mezzanine <glossary>bus<\/glossary>,\nit could replace either <glossary>ISA<\/glossary>,\n<glossary>EISA<\/glossary> or MCA\nbuses. Although in most cases, <glossary>PCI<\/glossary>\nis offered as a supplement to the existing <glossary>bus<\/glossary>\ntype. If you look at a motherboard with <glossary>PCI<\/glossary>\nslots, you will see that they are completely separate from the other\nslots. Whereas <glossary>VLB<\/glossary> slots are extensions of the existing slots.\n<img SRC=\"isa_pci.png\" WIDTH=256 HEIGHT=256\nBORDER=0> <br \/>Figure Comparison of ISA\/EISA <glossary>bus<\/glossary> slots to PCI\n<p>\nPCI offers additional advantages over the\nVLB as the <glossary>VLB<\/glossary>\ncannot keep up with the speed of the faster CPUs, especially if there are multiple\nVLB devices on the system. Because <glossary>PCI<\/glossary>\nworks together with the <glossary>CPU<\/glossary>\nit is much more suited to\nmulti-tasking operating systems like <glossary>UNIX<\/glossary>.\n Whereas the <glossary>CPU<\/glossary>\ncannot work independently if a <glossary>VLB<\/glossary>\ndevice\nis running.\n<p>Like <glossary>EISA<\/glossary>\nand <glossary>MCA<\/glossary>,\n <glossary>PCI<\/glossary>\nboards have configuration information built into the card. As\nthe computer is booting, the system can configure each card individually based\non system resources. This configuration is done “around” existing\n<glossary>ISA<\/glossary>, <glossary>EISA<\/glossary>\nand <glossary>MCA<\/glossary>\ncards on your system.\n<p>\nTo overcome a shortcoming <glossary>PCI<\/glossary>\nhas when transferring data, Intel (designer and chief proponent of PCI) has come\nup with a <glossary>PCI<\/glossary>\nspecific chip sets, which allows data to be stored on the PCI controller,\nfreeing the CPU to do other work. Although this may delay the start of the\ntransfer, however once the data flow starts, it should continue uninterrupted.\n<\/p>\n<question id=\"249\" text=\"For compatibility PCI slots are the same size as EISA.\" \/>\n<p>\nA shortcoming of <glossary>PCI<\/glossary>, is that <glossary>ISA<\/glossary>\nand <glossary>EISA<\/glossary>\ncards can be\nswapped for <glossary>VLB<\/glossary>\ncards, without any major problems. This is not so for the <glossary>PCI<\/glossary>\ncards. Significant\nchanges need to be made to both the <glossary>kernel<\/glossary>\nand device drivers to <glossary>account<\/glossary>\nfor the differences.\n<\/p>\n<p>\nWhen it first came out, a shortcoming of <glossary>PCI<\/glossary>\nwas the number of boards that are\navailable. The number\ngrew rapidly, and there are now more <glossary>PCI<\/glossary>\nboards than <glossary>ISA<\/glossary>\nboards\navailable. It is on its way to becoming a de facto standard if not de jure.\n<\/p>\n<p>\nOn the other hand, the <glossary>PCI<\/glossary>\n<glossary>bus<\/glossary>\nis not processor dependent. This allows\nPCI to be installed in Pentium machines, as well as Alpha machines and other\narchitectures. You can therefore run the same <glossary>SCSI<\/glossary>\n<glossary>host<\/glossary>\nadapter (or whatever). Since it is 64-bits wide, both the Pentium\nand Alphas are not slowed down (too much) by the <glossary>bus<\/glossary>.\n<\/p>\n<p>\nFor the most part, PCI devices are recognized when Linux fist starts up. You can display a list of all PCI devices by using the <command>lspci<\/command>.\nNaturally you need to ensure the driver for the device in question is installed on you system, but common PCI devices should be available by default.\n<\/p>\n","protected":false},"excerpt":{"rendered":"<p>PCI More and more machines you find on the market today are being built only with some form of PCI local buses. One advantage that PCI offers over VL-Bus is the higher performance, automatic configuration of peripheral cards, and superior … <a href=\"http:\/\/www.linux-tutorial.info\/?page_id=272\">Continue reading <span class=\"meta-nav\">→<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-272","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=\/wp\/v2\/pages\/272","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=272"}],"version-history":[{"count":1,"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=\/wp\/v2\/pages\/272\/revisions"}],"predecessor-version":[{"id":652,"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=\/wp\/v2\/pages\/272\/revisions\/652"}],"wp:attachment":[{"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=272"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}