13 Differences Between ISA and PCI

By Dominic Chooper on October 17, 2022

Both these protocols, ISA and PCI, are good to use for customizing the computers according to the respective and particular needs of the users.

This way, they simply do not have to spend money on features that they do not need or want to use.

However, both these protocols work in a notably different way being distinctly different in their respective features and functionalities.


The 13 Differences Between ISA and PCI

Differences Between ISA and PCI

1. Full Form

While ISA is the acronym for Industry Standard Architecture, PCI, on the other hand stands for Peripheral Component Interconnect.

2. Date of Creation

ISA was created way back in 1981 and has since been updated to serve as an interface to connect the add-on cards to the motherboards. Therefore, this is an older technology in comparison to PCI.

On the other hand, PCI was created in 1990 as a replacement of Video Electronics Standards Association or VESA Local Bus or VLB by the Intel researchers and used in towers and server stacks initially.

3. Physical Appearance

Considering the physical appearance of both ports, the black ISA ports are longer by about 2 inches than the PCI ports. This also makes the I/O cards connected via these ports a bit bulkier.

On the other hand, the white or light colored PCI ports are shorter and therefore the I/O cards that connect through these ports tend to be less bulky.

4. Operational Speed

The PCI bus is a bit faster in performance in comparison to the speed of operation of the ISA bus due to its double, and even quadruple bit width.

On the other hand, the ISA bus is comparatively slower in transferring data.

5. Basics

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The ISA follows the same old architecture of IBM and allows connecting video cards, network cards, other expansion cards, and additional serial port cards.

The PSI, on the other hand, is a 32 bit computer bus that allows connecting network hardware, modem, video graphics cards, sound cards, and Ethernet or wireless cards with SSDs faster than SATA Solid State Drives and others.

6. The Slots

The PCI slots can transfer data at a much higher rate than the ISA slots. Any available PCI slot supports the PCI cards.

On the other hand, ISA cards can only be used in an ISA slot that is of the same size of the card and are also much slower in transferring data in comparison to the PCI slots.

7. Bus

The ISA bus width is of 16 bits and has a clock speed of 8 MHz with a data transfer speed of 16 MB/s.

On the other hand, the PCI bus width is 64 bits and has a speed of 33 MHz with a data transfer speed of 1 GB/s.

8. Advantages

The advantages offered by the low cost ISA include compatibility with older systems which is why it is widely used.

In comparison, the advantages  offered by PCI include its easy plug and play feature.

9. Disadvantages

The disadvantages of ISA include the need for jumpers and DIP switches while that of the PCI are high cost and incompatibility with older systems.

10. DMA Channel Use

Enabling or disabling DMA channel is applicable only to the ISA bus and devices. On the other hand, the PCI device drivers do not allow using d_map_enable or d_map_disable services.

11. Controller

The concept of controller and worker devices do not apply to the PCI like it is in ISA.

12. Multiple Buses

The bridging capabilities of PCI allow connecting several PCI buses with the expansion hardware off the shelf. The PCI-to-PCI bridge chip helps to extend the number of plug-in slots and beat the load limitations.

However, in comparison, you will need to include more computers in the setup to make such types of expansions with ISA.

13. Configuration Requirement

It needs doing some manual configurations to use ISA technology which is not required in PCI.

The PCI technology was designed to allocate address information automatically to the hardware item connected to it.

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Which is More Useful – ISA or PCI?

Considering the latest developments in the computer industry, and when you place ISA and PCI head to head, it can be said that both PCI and ISA made some significant impact in the industry in their heydays.

It is however quite expected from PCI due to its benefits offered in terms of speed and performance and being a full 10-year younger technology.

It was thought that it would show no signs of letting up.

However, in spite of gaining considerable momentum, PCI is overshadowed by the PCI Express and Mini PCI Express. Still it is used by several users and industries.

On the other hand, ISA is also not doing well either and it is expected that it will come to a close pretty soon.

Though the new PCI systems are still equipped with a few ISA add-in slots, it is expected to be fewer and fewer in the future systems and one day may cease to exist.

Keeping these facts aside, PCI seems to be more useful due to the performance enhancements offered by it making them ideal for use in high-bandwidth applications as well as in DAQ or Data Acquisition applications.

There seems to be a lot of room for growth in the PCI front than it is in ISA making it a safer and more reliable platform to build a DAQ application on. There are certainly a lot of good cases piling up for PCI.

It is all due to the lower clock speed, the asynchronous bus architecture, and 16-bit addresses of the ISA that has let it down a bit.

Though the ISA bus peripherals are quite good for a few specific applications, the need for speed and higher data transfer pushed users towards PCI from ISA since it cannot handle transferring more than 400,000 data samples across the bus in a second either to or from the memory.

When things are pushed beyond the bandwidth confines of the ISA bus, compromises need to be made either for the memory or for time which results in system delays.

In such situations the data that cannot be transferred immediately is needed to be stalled or stored locally, or may be lost, simply.

With PCI, the mezzanine bus architecture that is not dependent on the bus specification of the processor allows the devices to access the memory of the system without needing any help from the Central Processing Unit.

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This relieves the load from the CPU allowing it to focus on other tasks and application calls.

The users can also acquire data at the same time and analyze the existing data in real time and still keep a constant communication with the other tasks on the network.

Data can be sent by the asynchronously running PCI peripherals though the 32-bit bus at a high speed since the PCI bus can support even the most modern, high bandwidth, and data intensive I/O applications including HDTV and 3D video.

All hardware settings are controlled in software with no additional need for jumpers and customizing the configuration of the systems can also be done easily during any stage of operation.

However, you can implement DAQ applications in your old ISA based system if you do not want to buy a new one especially if it is a single function and a low end application.

Nonetheless, DAQ applications usually need a higher and bidirectional data flow which calls for higher bandwidth which is offered by PCI.

On a PCI based PC with ISA slots, ISA being a secondary bus will receive secondary treatment when the peripherals are looking for a bus controller.

Therefore, PCI is ideal for higher throughput and speed in performance whether it is for DAQ applications or others due to its higher bandwidth capabilities.


Therefore, it can be concluded that though both ISA and PCI serve the same purpose they are very different from one another.

Now that you know the major aspects they differ in and some other relevant facts, it should be very easy for you to make out which is more useful between them.