Data Transfer Speed Control Apparatus Capable of Varying Speed of Data Transfer Between Devices Having Different Transfer Speeds

This invention relates to a data transfer speed control apparatus capable of varying speed data transfer speed between two devices, depending on the data transfer speeds of the two devices, and in particular to a data transfer speed control apparatus, which is suitable for the data transfer between devices the data transfer speeds of which are different or can be arbitrarily set, e.g. between a semiconductor storage device, such as an IC disc, etc., and a device of higher rank therefor.

As prior art techniques for mutually transferring data between two devices having different data sending/receiving speeds are known those disclosed by, for example "IBM 3380 Storage Control Models 1, 2, 3 and 4 Description Manual" (published 1985) p. 5-15 "Speed Matching Buffer for 3380", p. 5-14 "Speed Matching Buffer for 3375". According to these prior art techniques, e.g. in the case where data are mutually transferred between a channel device and a disc device, the difference in the data transfer speed between the channel device and the disc device is absorbed by disposing a large capacity data buffer within a control device controlling the disc device and by temporarily storing the data transferred between the channel device and the disc device in this data buffer.

An object of this invention is to provide a data transfer speed control apparatus by which data transfer between a channel device and a storage device can be in synchronism with each other and at the same speed equal to the maximum data transfer speed which is possible or available between the channel device and the storage device.

Another object of this invention is to provide a data transfer speed control apparatus which is suitable for the data transfer between a semiconductor storage device, such as an IC disc, having no rotating mechanism for the data storage medium and hence a transfer speed which can be varied, and a channel device.

Still another object of this invention is to provide a data transfer system within a computer requiring neither a large capacity data buffer in a control device nor complicated buffer control logic for controlling this data buffer.

Still another object of this invention is to provide a data transfer system, which is capable of eliminating deviations between the channel side operation and the disc side operation in the case where the troubles are produced and reporting the troubles to the channel at the proper timing at which the troubles are to be originally reported.

Still another object of this invention is to provide a data transfer system in which semiconductor storage devices having different transfer speeds can be connected with a control device for controlling the data transfer between a channel device and the semiconductor storage devices.

Still another object of this invention is to provide a storage subsystem within a computer capable of determining the data transfer speed after having fixed a data transfer path.

According to this invention the objects described above can be achieved in such a manner that a semiconductor storage subsystem in a computer system of the like is provided with which indicates or displays the maximum transfer capacity of each of plurality of channel devices and a plurality of semiconductor storage devices connected with a semiconductor storage control device and a mechanism which upon data transfer between one of the storage devices and one of the channel devices, the data transfer speed of each of the one storage device and the one channel device can be set to that one of the maximum transfer speeds of both the devices which is lower.

When the semiconductor storage control device receives an instruction to transfer data from one of the channel devices to one of the semiconductor storage devices, it reads out the indicated maximum transfer speed of the one channel device and the indicated maximum transfer speed of the one semiconductor storage device within the semiconductor storage control device and decides to transfer the data with the lower one of the maximum transfer speeds of the channel device and the semiconductor storage device, that i, the maximum speed which is possible or available between the channel device and the semiconductor storage device. A transfer speed determining logic section within the semiconductor storage control device sets the decided transfer speed in a transfer speed setting section for channel device and in a transfer speed setting section for semiconductor storage device within the semiconductor storage device. In this way, the channel device and the semiconductor storage device carry out mutually the data transfer in synchronism with each other and at the decided data transfer speed through the semiconductor storage control device.

Since the channel device and the semiconductor storage device can work so as to effect data transfer therebetween at the same speed in synchronism with each other, it is not required that the semiconductor storage control device is provided with a large capacity data buffer for absorbing speed difference in the speed between the channel device and the semiconductor storage device as well as any controller for controlling the data buffer. Furthermore, when a trouble or fault is produced, it is possible to report the trouble at a correct timing.

FIG. 1 is a block diagram illustrating the construction of an embodiment, in which this invention is applied to a semiconductor storage subsystem; and

FIG. 2 is a scheme for explaining how the data transfer speed is determined for a combination of a channel device and a semiconductor storage device.

An embodiment of a data transfer speed control apparatus according to this invention will now be explained by virtue of the accompanying drawings.

In FIG. 1 reference numerals 1 and 2 are CPUs; 3, 4 are channel devices; 5 is a semiconductor storage control device; 6, 7 are sections indicating or displaying the maximum transfer speeds of channel devices 3 and 4; 8 is a section setting actual transfer speeds of channel devices 3 and 4; 9 is a logic section determining a speed of data transfer to be actually made; 10, 11 are semiconductor storage devices; 12, 13 are sections displaying the maximum transfer speeds of semiconductor storage devices 10 and 11; and 14, 15 are sections setting actual transfer speeds of the semiconductor storage devices 10 and 11.

FIG. 1 shows the construction of a semiconductor storage subsystem in a computer system, to which this invention is applied. This semiconductor subsystem includes two semiconductor storage devices (hereinbelow abbreviated to SSU) 10 and 11 connected to a semiconductor storage control device (hereinbelow abbreviated to SSC) 5 and two channel devices 3 and 4 disposed in CPUs 1 and 2, respectively. The maximum data transfer speed is 6 MB/s (megabytes/second) for the channel device 3 and the SSU 10 and 3 MB/s for the channel device 4 and the SSU 11. The maximum data transfer speeds of the channel devices 3 and 4 are indicated by the channel maximum transfer speed indicating sections 6 and 7, respectively and the maximum data transfer speeds of the SSUs 10 and 11 are indicated by the SSU maximum transfer speed indicating sections 12 and 13 within the SSUs 10 and 11, respectively. These indications or displays are effected in such a manner that, in the step of connecting the relevant channel devices and the relevant semiconductor storage devices, jumper lines are mounted, only at those places of a plurality of connection line setting sections disposed on the channel maximum transfer speed indicating sections 6 and 7 within the semiconductor storage control device 5 which correspond to the specifications of the relevant channel devices and at those places of a plurality of connection line setting sections disposed on the relevant semiconductor storage devices 10 and 11 which correspond to the specifications of the relevant semiconductor devices. It is preferable to effect the mounting of the jumper lines on a circuit board.

Either one of the channel devices 3 and 4 can transmit a data transfer demand to the SSUs 10 and 11 through the SSC 5. Now it is supposed that the channel device 3 transmits the data transfer demand to the SSU 11. When the SSC 5 receives the data transfer demand from the channel device 3 to the SSU 11 through a control line indicated by a broken line in FIG. 1, the transfer speed determining logic section 9 within the SSC 5 reads out the channel maximum transfer speed indicating section 6 corresponding to the channel device 3 and knows that the channel device 3 has a data transfer capacity of 6 MB/s. Next it reads out the SSU maximum transfer speed indicating section 13 within the SSU 11 after having set a path to the SSU 11 and knows that the SSU 11 has a data transfer capacity of only 3 MB/s. The transfer speed determining logic section 9 decides to effect the data transfer with a data transfer speed of 3 MB/s, which is the lower one, and sets the data transfer speed of 3 MB/s in each of the channel transfer speed setting section 8 and the SSU data transfer speed setting section 15 within the SSU 11. In this way, the channel device 3 and the SSU 11 work with the data transfer speed of 3 MB/s to effect the data transfer in synchronism with each other by using a data line indicated by a full line in the figure through the SSC 5.

The SSC 5 decides an optimum data transfer speed, depending on the combination of the channel devices 3, 4 and the SSUs 10, 11, in the same way as stated previously, so that transfer data between the combined channel device and SSU is effected with the optimum speed. The data transfer speed decided by the combination of the channel devices 3, 4 and the SSC 10, 11 in the embodiment indicated in FIG. 1 is indicated in FIG. 2. The data transfer speed is 6 MB/s for the combination of the channel device 3 and the SSU 10 and it is 3 MB/s for all the other combinations.

The indication of data transfer speed may also be achieved by mounting a group of microswitches on the connection line setting sections and turning-on only the switches corresponding to the data transfer speeds of the channel device and the semiconductor storage device connected with each other.

Although in the above a pair of 3 MB/s and 6 MB/s is described as the kind of data transfer speeds, it is of course possible to use a semiconductor storage subsystem provided with another combination of other speeds such as 1.5M, 3M, 4.5M, 6M, . . . B/s.

Further, the name of type of storage capable of specifying the data transfer speed of the semiconductor storage device may be set in a coded form in the connection line setting section of the semiconductor storage device.

In the above, this invention has been explained, supposing that the number of the maximum data transfer speeds of the devices is 2 in an embodiment, in which this invention is applied to a semiconductor storage subsystem consisting of 2 channel devices, 2 SSU and 1 SSC. However this invention is not restricted to the embodiment stated above, but it can be applied to any semiconductor storage subsystem indicating a combination or arbitrary numbers of channel devices, SSUs and SSCs. Further the number of the maximum data transfer speeds of a plurality of devices constituting the system is not restricted to 2, but it may be greater than 2. Furthermore, this invention may be applied not only to the data transfer in a semiconductor storage subsystem but also to the data transfer in any system including a plurality of devices the data transfer thereof are variable or different.