USB vs. Serial and Parallel

Contents

• Comparison
• Parallel Port
• Serial Port

Total Phase is pleased to offer USB on all its devices. USB is the new standard for connecting peripherals to your computer. It easily outperforms the serial and parallel port on your computer.

Comparison

Here is how USB stack up against other protocols available for other host adaptors:

	USB	Serial	Parallel
Industry Standard	Yes	Yes	No
Bandwidth	12 Mbps	115 Kbps	115 KBps EPP/ECP - 3 MBps
Number of Devices	127 devices on a single USB bus	Limited to the number of ports available on the computer.	Limited to the number of ports available on the computer.
Bus Power	Yes, can provide up to 500 mA at 5V	No	No
Cable Length Limit	5 m / 16.4 ft	3 m / 10 ft	1.8 m / 6 ft
Plug'n'Play	Yes	No	No
Hot Swapable	Yes	No	No

Serial

The serial port does not suffer the same problems of the parallel port. The behavior of the serial port has been standardized across computers so there are no surprises there. The real problems are: bandwidth and limited ports. The serial port is the slowest of the group. If you have a host adaptor that claims to support 400 kbps, consider the fact that the serial port can only support 115 kbps. That just doesn't add up.

Parallel

The Parallel port can be fast enough for most applications, but it suffers from many problems. The most significant issue is that the port is non-standard. Often times, users of the parallel port will run into OS issues or BIOS issues. And good luck trying to use the parallel port on your laptop computer. Most manufacturers have different implementations of the parallel port. On most computers there is usually only one parallel port available which can cause many headaches if that port needs to be shared with a printer or scanner.