Electrical computers and digital data processing systems: input/ – Intrasystem connection – Bus interface architecture
Reexamination Certificate
2000-11-01
2004-12-07
Lefkowitz, Sumati (Department: 2112)
Electrical computers and digital data processing systems: input/
Intrasystem connection
Bus interface architecture
C370S235000, C370S394000, C714S748000
Reexamination Certificate
active
06829670
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-327178, filed Nov. 17, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a computer system and a data transfer control method. In particular, the present invention relates to an improved computer system and an improved data transfer control method so that data required to transmit a bus transaction can be transferred accurately and speedily.
In recent years, there has been developed a variety of personal computers (hereinafter, referred to as a notebook type PC) that can be easily portable and operable by batteries. Some notebook type PCs are configured so that these PCs can be attached to an expansion unit in order to ensure their functional expansion as required. In order to ensure that a resource of an expansion unit can be efficiently used from a notebook type PC, it is essential to connect a bus of the notebook type PC to a bus in the expansion unit. By this bus connection, a device on the bus in the expansion unit can be handled in the same way as the device in the notebook type PC.
In many personal computers, a PCI (Peripheral Component Interconnect) bus is used. Therefore, it is general that bus connection between the notebook type PC and the expansion unit is made by providing docking connectors having a large number of pins corresponding to the number of signal lines included in the PCI bus on the notebook type PC side and the expansion unit side, respectively, and then, physically connecting both PCI buses via the docking connectors.
However, in this configuration, a large area is required for mounting a docking connector, which is disadvantageous in achieving small sized and thinner notebook type PC. Further, connector mount positions of the notebook type PC side and the expansion unit side must be aligned with another, restriction will apply to a physical cabinet structure in carrying out new product development.
Recently, there has been proposed by the Applicant a technique in which a PCI-PCI bridge for making connection between a PCI bus on the notebook type PC side and a PCI bus on the expansion unit side is composed of two controllers, i.e., first and second controllers that are physically different from each other, and transmission of information between these controllers is performed through serial transmission (Japanese Patent Application No. 11-183919 and U.S. patent application Ser. No. (not assigned yet) filed on Jun. 28, 2000). In this case, the two controllers, i.e., the first and second controllers are disposed separately on the notebook type PC side and expansion unit side. Data required to transmit a bus transaction from the PCI bus on the notebook type PC side to the PCI bus on the expansion unit side is transmitted to the second controller via a serial transmission path such as a cable after being converted from parallel data into serial data at the first controller. In the second controller, conversion from serial data into parallel data is performed, and a bus transaction is executed on the PCI bus on the expansion unit side. In this manner, the notebook type PC and the expansion unit can be connected to each other via a thin cable with its small number of signal lines.
However, in the case where a single PCI-PCI bridge is composed of two controllers, i.e., the first and second controllers that are physically different from each other, it is required to ensure data transfer between these two controllers in order to maintain reliability in system operation. Further, a data transfer speed between these two controllers greatly influences throughput of the entire system. Hence, implementation of a new flow control for transmitting data required to transmit a bus transaction accurately and speedily between two controllers is required.
Many of the data transfers in the fields of computer or communication are performed by employing a handshake. If a receiving party detects an error, it transmits NACK (Negative ACK) to a transmitting party. If the transmitting party receives NACK, it performs a re-transmission processing. If the receiving party receives data correctly, it transmits ACK (Acknowledgment) to the transmitting party. If the transmitting party receives ACK, it goes to the next data transmission processing. However, in such system, although its implementation is easy, it is difficult to obtain a sufficient communication speed be aware of the nature of the handshake process.
BRIEF SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a computer system and a data transfer control method in which a new flow control is implemented such that data required to transmit a bus transaction between buses can be transmitted accurately and speedily between two controllers, thereby ensuring sufficient throughput and improvement of operation.
According to the present invention, there is provided a computer system for transferring data required to transmit a bus transaction between first and second controllers, the computer system comprising: data transmitting means for assigning consecutive IDs to a plurality of data targeted for transmission, respectively, thereby sequentially transmitting a plurality of these data from a transmitting controller to a receiving controller without waiting for return of a response from the receiving party; response transmitting means for, each time data is received correctly, transmitting the response to which the same ID as that of the received data has been assigned, from the receiving controller to the transmitting controller; and means for managing whether or not the response is returned from the receiving controller for each transmitted data, and, when a re-transmission request is received from the receiving controller, for re-transmitting data for which the response is not received from the receiving controller in order of IDS.
In this computer system, a consecutive ID is assigned to data at the transmitting controller, and is transmitted to the receiving controller. In this case, there is no need to wait for a response from the receiving controller every data transmission, and a plurality of data are transmitted to the receiving controller sequentially irrespective of the response. The receiving controller basically returns a response to the transmitting party every correct data reception. In this case, an ID corresponding to the received data is assigned to such response. This is because return of the response can be executed asynchronously with data transmission from the transmitting party. Hence, the transmitting party can perform next data transmission without waiting for a response from the receiving party.
Further, the transmitting party can recognize whether or not the response is returned from the receiving controller by each transmitted data by employing an ID assigned to the response. Thus, as in a general handshake, whether or not the data is correctly received can be known for individual data. In addition, the transmitting party can determine which data item is the last the receiving party has received. Thus, for example, the case where the receiving party cannot receive data due to a buffer overflow on the receiving buffer, data that is not received can be re-transmitted. Hence, improvement in communication speed can be made compatible with improvement in reliability.
Hence, a mechanism of the above flow control is applied to two physically different controllers that configure a bus bridge, thereby making it possible to transfer data required to transmit a bus transaction speedily and accurately. Serial connection between a host device and an expansion unit can be achieved while a bus bridge maintains its operational reliability and performance.
At the transmitting party, even after the data is transmitted, the transmitted data may be managed as data waiting for a response until the corresponding response has been received.
In addition
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
Lefkowitz Sumati
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