Electronic digital logic circuitry – Signal sensitivity or transmission integrity – Bus or line termination
Reexamination Certificate
1998-09-30
2001-05-08
Tokar, Michael (Department: 2819)
Electronic digital logic circuitry
Signal sensitivity or transmission integrity
Bus or line termination
C326S086000
Reexamination Certificate
active
06229334
ABSTRACT:
RELATED APPLICATIONS
The present application is related to a co-pending application entitled “VOLTAGE OVERSHOOT CONTROL IN HOT PLUG SYSTEM”, U.S. Ser. No. 09/163,922, filed on even date herewith and assigned to the assignee of the present application. Subject matter disclosed but not claimed herein is disclosed and claimed in the related application.
FIELD OF THE INVENTION
The present invention relates generally to information processing systems and more particularly to a system architecture which includes means for controlling voltage overshoot.
BACKGROUND OF THE INVENTION
Computer environments which contain many reactive elements must be treated as a non-terminated, transmission line environment. Thus, a signal must travel to the end of a signal line and be reflected back or return to the driver before the signal is considered “switched”. This environment is conducive to “ringing”, which, in turn, under certain conditions, causes relatively large voltage “overshoots” to occur in switching between voltage levels. As used herein, the term “overshoot” refers to the initial and/or trailing edges of a signal temporarily greatly exceeding the steady state voltage level to which the signal is transitioning.
The PCI (Peripheral Component Interconnect) computer system specification (“PCI Local Bus Specification”, Revision 2.1, dated June, 1995), is an example of a computer environment which contains many reactive elements. The PCI Specification defines limits and tolerances for compliance with the Specification. The PCI Specification for 33 MHz devices defines that the maximum voltage overshoot allowed is +11 volts for a maximum of 11 nsec. This is considered the “worst case” situation for the PCI bus. This limitation presents a problem for “universal” PCI add-in cards, which must include 3.3 volt technology that is “5 volt tolerant”, and therefore subject to the 11 volt maximum overshoot. Typically, clamping diodes are implemented to limit voltage overshoots. However, with the increased overshoot exposure with 3.3 volt devices, the clamping diodes on the universal adapters or cards can fail over time due to the excessive current flow caused by the overshoot voltages (metal migration).
Thus there is a need for an enhanced computer system and methodology which is designed to control voltage overshoot problems in computer systems.
SUMMARY OF THE INVENTION
A method and implementing computer system configuration is provided in which PCI bus load conditions are detected and load devices are selectively connected to the PCI bus to dampen lightly loaded systems and limit voltage overshoots on the PCI bus.
REFERENCES:
patent: 3711834 (1973-01-01), Rogers
patent: 5089766 (1992-02-01), Iwatani
patent: 5418403 (1995-05-01), Morell, III
patent: 5612634 (1997-03-01), MacKenna
patent: 5646572 (1997-07-01), Masleid
patent: 5920266 (1999-07-01), Allgood et al.
patent: 5996035 (1999-11-01), Allen et al.
IBM Technical Disclosure Bulletin vol. 29 No. 10 Mar. 1987 “Power On/Off Sequencing of Dual Voltage Regulators”.
IBM Technical Disclosure Bulletin vol. 26 No. 5 Oct. 1983 “Laser Diode Controller”.
Kelley Richard Allen
Neal Danny Marvin
International Business Machines - Corporation
Tokar Michael
Tran Anh
Van Leeuwens Leslie A.
Wilder Robert V.
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