Internal Bus - From ISA to PCI

Internal data communications paths and their performance rates are just as important as external data pathways. ISA - the original bus standard for connecting components and peripherals was introduced in 1982.

It was designed for the original 286 computer. Its 16-bit / 8 MHz performance rates could cope with the vast majority of computing needs. For the nascent demands of mobile computing world, it was more than fast enough.

It didn't take long, however, for processors to become faster and applications more compute-intensive. ISA started to be a bottleneck slowing data computing down. Alternative enhanced bus standards such as EISA and Micro Channel were introduced to alleviate this situation but could not gain market acceptance. Enter PCI - a new local bus technology introduced by Intel in 1993.

Bursting with Speed

PCI offers users clear advantages. It can move 32 bits of data at 33 MHz. Moreover, it can support multiple peripheral components and add-in cards at a peak bandwidth of 132 MB per second - a substantial improvement over the 5 MB per second transfer rates offered by the standard ISA bus.

Unlike ISA, PCI also supports a method of transferring data called linear bursts, which ensures that the bus is continuously filled with data. This means that large amounts of data are read from - or written to - a single address. This allows more bandwidth to be used to send data rather than address data. With this increased performance, it was evident that the PC industry would embrace PCI. In the last year, mobile PC users have also begun to experience the benefits of PCI.

Modern notebooks and docking stations using PCI technology offer users increased performance and plug and play benefits. The standard was designed with integrated plug and play specifications. Not only can cards and devices be added with automatic recognition, but the notebooks themselves can be docked and undocked at will, with plug and play operating systems, such as Windows95, automatically adjusting their configuration.

The benefit of PCI for notebook users is not having to worry about reconfiguring their machines. Wherever they are - whether in hotel, in the office or at home- their notebook systems adjust to the hardware available. Moreover, all of this flexibility can be had with added performance.

Proprietary expansion - the company's solution

In the days of industry wide and multi-industry standards, proprietary expansion may seem to have only a small role in connectivity solutions. In fact proprietary connectivity sockets are now few and far between. Proprietary expansion standards, however, offer also connectivity in an indirect way through additional slots. Toshiba, as the market leader in mobile PCs, has the advantage that other companies are prepared to build to the standards we set.

Thus when Toshiba sets an expansion bus for a range of notebooks, not only do our own expansion units appear, but third party combinations emerge to fill market niches. The ISA-based connector for the T4 series of notebooks from 1991 to 1995 produced various units. The new ISA-based connectors on the Satellite models and the PCI-based ports on the Tecra/Portégé models also attract extra solutions. In the last year, Toshiba's internal expansion slot, the SelectBay, has also attracted a great deal of attention with several third parties reverse engineering options to fit.

Of course this improved choice only provides a further reason for purchasers to choose the market leader. As well as the manufacturer's hardware, third parties niche products may supply just the solution you need, especially if you are in a large industry. All of Toshiba's expansion units provide a wide range of industry standard connectivity methods, ranging from PC Cards, to ISA and PCI expansion slots, SCSI 2 connections and during 1997 USB hub functions. Buyers of these solutions need never fear being left with no connectivity support.