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  • ISA vs. PCI

One of the most advantageous features of personal and business computers is their flexibility and expandability. Expansion cards, input/output cards and other hardware upgrades that use the ISA or PCI protocol allow users to customize their computers to meet their specific needs without having to pay for features they don’t want or need. This article provides a brief background on ISA and the latest standard in I/O cards, PCI.

History of ISA
The ISA (Industry Standard Architecture) port has been nearly as long as the PC itself. Created in 1981 and updated in 1983, the ISA standard served as an interface between add-on cards and motherboards. ISA proved to be a harbinger of an explosion in consumer add-on component demand. While other standards were produced, e.g., AGP and VLB, ISA endured as the most supported and utilized I/O standard. This was helped along due heavy investment by industry and military institutions. Consequently, though practically extinct on PCs and laptops, motherboards are still produced with ISA. Many specialized industry and military situations still require the old standby, ISA. ISA has also proven to be a reliable standard that has been leveraged by subsequent technologies. All modern internal hard drives use some variant of the specifications.

History of PCI
PCI (Peripheral Component Interconnect) was created in 1990 by Intel researchers as a replacement for VLB (VESA Local Bus). It first gained popularity for use in server stacks and towers. However, even with its improvements over VLB, it did not gain significant market share in the consumer sector until 1994, with the introduction of Pentium PCs. In 1995, it replaced NuBus as Apple’s choice for expansion. Since then, PCI has undergone a number of version upgrades, with PCI 1.0 giving way to PCI 2.0 and finally, in 2004, PCI-E was introduced. PCI-E represents a significant step away beyond PCI 1.0—in fact, PCI-E is not backwards compatibility with PCI 1.0 and PCI 2.0 ports. As such, PCI and PCI-E still co-exist on many motherboards. Mini-PCI-E has made strides in replacing PCI, and is expected to overtake PCI-E in the near future.

ISA and PCI Compared
For many years, ISA and PCI were equivalents. Because PCI was introduced as a complement to, rather than a direct competitor to ISA, it is not uncommon for motherboards to have both ISA and PCI ports. ISA, at least for a time, was concurrent with the PCI standard. ISA would give better performance in some areas, while PCI yielded better performance in other areas.

In physical appearance the ISA and PCI ports are vastly different. The ISA is longer (by about two inches), and thus the I/O cards that connect via ISA tend to be bulkier as well. Their differences do not stop there. PCI is a significantly faster (in theory) bus. PCI has double (or in rare instances, quadruple) the bit-width, resulting in faster data transfer.

When placed head-to-head, PCI is definitely the better and faster option. Which is to be expected, considering PCI is a full ten years newer. While, in 2010, ISA is practically obsolete and PCI is well on its way to extinction as PCI-E and Mini-PCI-E gain steam, they are still in use by many consumers and industries. ISA and PCI made a significant impact on the computer industry.