Texas Memory Systems XP-15 manual Appendix B PCI Local Bus Specifications

Appendix B – PCI Local Bus Specifications

The XP-15 interface adapter is a 3.3V signaling environment expansion card, as defined by the PCI Local Bus Specification 2.0, 2.1, and 2.2. This means that the XP-15 is designed to operate exclusively in 3.3V signaling environment system motherboards.

During the development of the XP-15, the liberty was taken to add a second key slot on the PCI edge connector. This allows for operation and testing in most 5V signaling environment motherboards that provide a 3.3V power rail. This is neither a recommended nor a supported configuration.

The following table clarifies the requirements for system motherboards under the different revisions of the PCI Specification.

System Motherboards	5V Signaling Environment	3.3V Signaling Environment
PCI Local Bus	+5V, +12V, and -12V required.	+5V, +3.3V, +12V, and -12V rails
Specification 2.0	+3.3V may either be included with	are all required.
	system, or a means to add it
	afterwards must be provided.
PCI Local Bus	+5V, +12V, and -12V required.	+5V, +3.3V, +12V, and -12V rails
Specification 2.1	+3.3V may either be included with	are all required.
	system, or a means to add it
	afterwards must be provided.
PCI Local Bus	+5V, +3.3V, +12V, and -12V rails	+5V, +3.3V, +12V, and -12V rails
Specification 2.2	are all required.	are all required.

The following table clarifies the requirements for expansion cards in the different signaling environments.

Expansion Cards	5V Signaling Environment	3.3V Signaling Environment
5V Expansion Card	I/O Buffers are powered by the 5V	5V Expansion Cards are not
	power rail.	designed to work in a 3.3V
	2.0,2.1: +5V, +12V, -12V supplied.	signaling environment.
	If +3.3V is needed, expansion card
	must provide its own 3.3V.
	2.2: +5V, +3.3V, +12V, and -12V
	rails are all supplied.
3.3V Expansion Card	3.3V Expansion Cards are not	I/O Buffers are powered by the
(XP-15)	designed to work in a 5V signaling	3.3V power rail.
	environment.	+5V, +3.3V, +12V, and -12V rails
		are all supplied.
Universal Expansion	I/O Buffers are powered by the 5V	I/O Buffers are powered by the
Card	power rail.	3.3V power rail.
	2.0,2.1: +5V, +12V, -12V supplied.	2.0,2.1: +5V, +12V, -12V supplied.
	If +3.3V is needed, expansion card	If +3.3V is needed, expansion card
	must provide its own 3.3V.	must provide its own 3.3V.
	2.2: +5V, +3.3V, +12V, and -12V	2.2: +5V, +3.3V, +12V, and -12V
	rails are all supplied.	rails are all supplied.

Texas Memory Systems recommends the XP-15 adapter for use in 3.3V signaling environments.

XP15 User Guide Texas Memory Systems, Inc. (8/6/01) B-1