the responsibility of the PCI Special Interest Group (PCI-SIG). PCI and PCI-X sometimes are referred to as either Parallel PCI or Conventional PCI to distinguish them technologically from their more recent successor PCI Express, which adopted a serial, lane-based architecture. PCI's heyday in the desktop computer market was approximately 1995 to 2005. PCI and PCI-X have become obsolete for most purposes; however in 2020 they are still common on modern desktops for the purposes of backward compatibility and the low relative cost to produce. Another common modern application of parallel PCI is in industrial PCs, where many specialized expansion cards, used here, never transitioned to PCI Express, just as with some ISA cards. Many kinds of devices formerly available on PCI expansion cards are now commonly integrated onto motherboards or available in USB and PCI Express versions. History Work on PCI began at the Intel Architecture Labs (IAL, also Architecture Development Lab) . A team of primarily IAL engineers defined the architecture and developed a proof of concept chipset and platform (Saturn) partnering with teams in the company's desktop PC systems and core logic product organizations. PCI was immediately put to use in servers, replacing Micro Channel architecture (MCA) and Extended Industry Standard Architecture (EISA) as the server expansion bus of choice. In mainstream PCs, PCI was slower to replace VLB, and did not gain significant market penetration until late 1994 in second-generation Pentium PCs. By 1996, VLB was all but extinct, and manufacturers had adopted PCI even for Intel 80486 (486) computers. EISA continued to be used alongside PCI through 2000. Apple Computer adopted PCI for professional Power Macintosh computers (replacing NuBus) in mid-1995, and the consumer Performa product line (replacing LC Processor Direct Slot (PDS)) in mid-1996. Outside the server market, the 64-bit version of plain PCI remained rare in practice though, although it was used for example by all (post-iMac) G3 and G4 Power Macintosh computers. Later revisions of PCI added new features and performance improvements, including a 66 MHz 3.3 V standard and 133 MHz PCI-X, and the adaptation of PCI signaling to other form factors. Both PCI-X 1.0b and PCI-X 2.0 are backward compatible with some PCI standards. These revisions were used on server hardware but consumer PC hardware remained nearly all 32-bit, 33 MHz and 5 volt. The PCI-SIG introduced the serial PCI Express in . Since then, motherboard manufacturers have included progressively fewer