PC parallel interface works at ATM speeds

By Ron Wilson

Mountain View, Calif. - An interface-controller chip from NEC Electronics Inc. promises point-to-point links between PCs up to 100 meters apart at speeds approaching those of ATM networks. The Transprocessor uses a loop-back signaling technology to transfer data over a parallel cable at sustained rates of 2.5 Mbytes/second. The first application will be in a PC Card95 card that links notebooks to large machines, making server data available to the notebook at the speed of the local disk drive
The chips works on an elegantly simple principle. Attaching to a 16-bit parallel cable, the chip sends out a byte of data over one set of 8 lines on the cable. It then waits for the device on the other end of the cable to echo the data back on the 8 data wires. When correct data arrives, the chip moves on to the next byte.
Since the transfer is effectively self-timed, the chip will adjust to different lengths of cable or different hardware on the recieving end. Ideally, a user would transfer data a short distance between two Transprocessor chips over NEC's proprietary, thin 25-wire cable. But the company has used the chip to communicate with standard PC parallel port, used it with standard ribbon cable, and used it as distances up to 100 meters. Those stresses simply reduce the transfer rate.
The first version of the chip comes with a PC Card95 interface, the cable interface and an interface to an optional 64k x 16 program ROM. In that form, it drops nicely into a Type-1 PCMCIA card.
Using the card, developers said, a notebook-computer owner can connect to a desktop of file server and have access to the larger machine's disks at the same speed as the local disk in the notebook.
The current form of the chip is for point-to-point links only. But the developers plan a multidrop version of the Transprocessor in the near future that would function like a LAN, but at higher speed, and without the over-head and expense.
The transfer engine in the Transprocessor was designed by Trans Digital Corp. (Fremont, Calif), which will also supply th chip-with flash ROM and software-on a PC Card95 for $149. NEC will provide the bare chip, available in a 100-pin TQFP for $10 each in 10,000-unit lots.

Electronic Engineering Times, November 13, 1995.