Electrical computers and digital data processing systems: input/ – Intrasystem connection – Bus expansion or extension
Reexamination Certificate
2000-08-10
2004-08-03
Vo, Tim (Department: 2181)
Electrical computers and digital data processing systems: input/
Intrasystem connection
Bus expansion or extension
C710S301000
Reexamination Certificate
active
06772263
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a Hot Plug controller, and specifically to a Hot Plug controller that provides Hot Plug capability to an expansion slot on a PCI bus without an associated load on the PCI bus.
2. Description of the Related Art
A peripheral component interconnect (PCI) bus is an industry standardized expansion bus that conveys much of the information and signals of a computer system. In light of the miniaturization of computer systems, leading to notebooks and palm computers, expansion cards were created to provide memory space and/or input/output devices to expand the systems' functionality. The term “PCI Hot Plug” refers to the process of inserting, removing, or replacing the PCI expansion cards in a computer system without having to turn off the system.
The logic necessary to implement the PCI Hot Plug includes a Hot Plug controller in addition to a number of discrete components. These components typically include bus switches for isolating the expansion cards from the PCI bus, a power controller and associated field effect transistors (FETs) for controlling the power supply to the expansion cards, and light emitting diodes (LEDs) for indicating the state of the expansion cards. One of the functions of the Hot Plug controller is to monitor and control the activity of the PCI bus during the insertion, removal, or replacement of an expansion card.
FIG. 1
illustrates a typical Hot Plug bus system
100
including a PCI bus
104
, two expansion cards
102
A and
102
B connected to PCI bus
104
via slots
103
A and
103
B, respectively, and a Hot Plug controller
101
coupled to slots
103
as well as to PCI bus
104
via a bus
108
.
Hot Plug controller
101
controls a number of critical operations associated with slots
103
A and
103
B via connectors
105
A and
105
B, respectively. Specifically, in each set of connectors
105
, one connector controls power and the other connector controls PCI bus signals. Thus, by using connectors
105
A for example, Hot Plug controller
101
can control the power and PCI bus signals for slot
103
A and associated expansion card
102
A. Connectors
105
typically include bus switches (i.e., transfer gates) implemented by FETs. When a FET is turned on, it functions similar to a 5 Ohm resistor. However, when a FET is turned off, it functions similar to a 1 MOhm resistor.
In this manner, Hot Plug controller
101
can isolate an individual slot
103
(and hence its associated expansion card
102
) from PCI bus
104
and can power down each card
102
during insertion, removal, or replacement. Moreover, Hot Plug controller
101
provides the power-up and power-down sequences for expansion cards
102
to meet the electrical requirements of PCI bus
104
. Hot Plug controller
101
also provides additional signals to expansion cards
102
. Although only the reset signal PRST is shown, other signals well known to those in the art are also provided. Exemplary signals are described in detail in “PCI Hot-Plug Application & Design”, by Alan Goodrum, pages 31-37, published by Annabooks in 1998, and incorporated by reference herein. Finally, Hot Plug controller
101
generates a state indicator
106
(indicating slot power on or slot power off) as well as an attention indicator
107
(providing a predetermined color or flashing light) to draw a user's attention to a particular slot
103
(indicating card inserted or swap ready).
Note that Hot Plug controller
101
is controlled by software (not described in detail herein, but well known to those skilled in the art). In this manner, a user can provide requests to a standard peripheral device of a computer system, such as a keyboard, and the corresponding request is translated into software, which is then provided to Hot Plug controller
101
.
The PCI Hot Plug specification supports three different types of operations: Hot Add, Hot Remove/Delete, and Hot Swap. In a typical computer system, to provide the above-described operations, Hot Plug controller
101
monitors PCI bus
104
. A typical Hot Plug controller
101
monitors these signals directly via bus
108
, thereby providing an electrical load on PCI bus
104
.
The PCI bus specification defines ten (10) electrical loads as a maximum limit when PCI bus
104
operates at 33 MHz and five (5) loads at 66 MHz. Each slot
103
is counted as two loads (a first load for expansion card
102
and a second load for connectors
105
). Moreover, in a typical PCI bus, at least one master (explained in detail below) is connected to PCI bus
104
. Thus, at 66 MHz, system
100
cannot provide Hot Plug capability because the maximum number of loads would be exceeded. Because the electrical loads on a PCI bus are at a premium, a need arises for a system and method to decrease the number of loads on the bus, thereby allowing Hot Plug capability at maximum speed and increasing system functionality.
SUMMARY OF THE INVENTION
In accordance with the present invention, a Hot Plug system includes a PCI bus, an expansion card, a slot for receiving the expansion card, and a Hot Plug controller directly connected to the expansion card and the slot, but only indirectly connected to the PCI bus.
The present invention uses an enhanced arbiter to monitor and control the PCI bus on behalf of the Hot Plug controller, thereby allowing the Hot Plug controller to be disconnected from the PCI bus and reducing a critical load on the PCI bus. Because the Hot Plug controller no longer needs to perform monitoring and controlling functions on the PCI bus, the logic within the Hot Plug controller can be significantly simplified. However, the Hot Plug controller of the present invention still maintains direct control over the expansion slots and associated expansion cards. In one embodiment, the enhanced arbiter with Hot Plug capability is implemented with a bridge on a chipset.
REFERENCES:
patent: 5784576 (1998-07-01), Guthrie et al.
patent: 6035355 (2000-03-01), Kelley et al.
patent: 6170029 (2001-01-01), Kelley et al.
patent: 6286066 (2001-09-01), Hayes et al.
patent: 6338107 (2002-01-01), Neal et al.
patent: 6363452 (2002-03-01), Lach
patent: 0 990 973 (2000-04-01), None
patent: 1 011 050 (2000-06-01), None
European Search Report for Application No. EP 01 25 0290 dated Sep. 16, 2003.
Alan Goodrum, “PCI Hot-Plug Application & Design,” Annabooks, p. 31-50, (1998).
Christie Parker & Hale LLP
ServerWorks Corporation
Vo Tim
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