Gunning transceiver logic

Gunning Transceiver Logic or GTL is a type of logic signalling used to drive electronic backplane buses. It has a voltage swing between 0.4 volts and 1.2 volts, much lower than that used in TTL and CMOS logic, and symmetrical parallel resistive termination. The maximum signalling frequency is specified to be 100 MHz, although some applications use higher frequencies.

GTL is defined by JEDEC standard JESD 8-3 (1993).

The bus used in the Pentium Pro, Pentium II and Pentium III processors made by Intel uses GTL+ (or GTLP, developed by Fairchild Semiconductor), an upgraded version of GTL which has defined slew rates and higher voltage levels.

Reference

• Fairchild Semiconductor, Application Note AN-1070, GTLP vs. GTL: A Performance Comparison from a System Perspective, 1997