JP2794052B2 - Control device for magnetic disk drive - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a controller for writing data to or reading data from a magnetic disk device.

"Conventional technology" Conventionally, in this type of control device, a central processing unit (CP
A memory such as U) may not be able to use a magnetic disk, but the magnetic disk needs to write / read data at a constant rate at a constant rotation speed. Therefore, a buffer called FiFo (First in First out) is provided between the memory 11 and the magnetic disk device 12 as shown in FIG.
13 is interposed, and at the time of writing, write data is intermittently sent from the memory 11 to the FiFo buffer 13, and after the buffer 13 of the FiFo is filled with data, the data is continuously transferred from the FiFo buffer 13 to the magnetic disk device 12. Send and write.
At the time of reading, data continuously read from the magnetic disk device 12 is stored in the FiFo buffer
Is transferred to the memory 11 intermittently. For example, the writing speed of the magnetic disk device 12 is
In order to write 1.5 Mbytes of data to the magnetic disk device 12 when the data transfer speed is 1.5 times faster than the data transfer speed between the two, there is a shortage of 0.5 Mbytes of data.
After prefetching in advance to the Fo buffer 13, the write data is transferred from the FiFo buffer 13 to the magnetic disk device 12.

[Problem to be Solved by the Invention] Conventionally, the memory 11 is transferred from the memory 11 to the magnetic disk device 12.
When the amount of data to be written in each transfer is the maximum amount, the data amount at which data shortage occurs is determined as the capacity of the FiFo buffer 13. Fi
Since the Fo buffer 13 sends the data to the magnetic disk device 12 after the data is full, in the case of write data with a small transfer amount at one time, the data is prefetched to an unnecessary amount for the transfer and the FiFo buffer There is a problem that it takes time for the disk 13 to become full and writing to the magnetic disk device 12 is delayed.

[Means for Solving the Problems] In the magnetic disk drive according to the present invention, when data of one transfer data amount M is sent from the CPU to the FiFo buffer at the speed Vi and the FiFo buffer becomes full, In the control device of a magnetic disk drive that writes the output data of the FiFo buffer to the magnetic disk at a speed Vo higher than the speed Vi, the physical capacity No of the FiFo buffer itself is determined by the maximum transfer data amount Mm and the speed Vi at one time. Shortage Nm determined by speed Vo =
Mm (1-Vi / Vo) is selected at least larger than Mm (1-Vi / Vo). For one transfer data amount M (M <Mm), the used capacity N of the FiFo buffer is calculated as follows: N = M (1-Vi / Vo) Is provided.

FIG. 1 shows an embodiment of the present invention. As shown in FIG. 1, a variable capacity FiFo buffer 14 is interposed between the memory 11 and the magnetic disk device 12 in the present invention. When data is transferred from the memory 11 to the magnetic disk device 12, the transfer amount, for example, the number of transfer blocks, is sent from the CPU 15 to the microprocessor 17 of the disk control device 16, and the microprocessor 17 stores N% of the input transfer amount. Is calculated, and the calculation result is set as the capacity of the variable capacity FiFo buffer 14. This N is the data channel speed Vi from the memory 11 to the FiFo buffer 14, and the write / read speed Vo of the magnetic disk device 12.
From this, it is calculated as (1−Vi / Vo) × 100.

The variable capacity FiFo buffer 14 is configured, for example, as shown in FIG. The write command from the terminal 18 is counted by the write address counter 19, and the read command from the terminal 21 is counted by the read address counter 22. Write command from terminal 18 and read command from terminal 21
When the two commands conflict, one is delayed. When the two commands do not conflict, the multiplexer 24 is controlled in accordance with the input command, and the output of the write address counter 19 or the read address counter 22 is selected. The data is supplied to the RAM 25 as an address. When a write command is issued, write data (data from the memory 11) is written into the RAM 25 at the address from the write address counter 19 at that time, and when a read command is issued, the read address counter at that time is written. The RAM 25 is read from the address 22, and the read data is sent to the magnetic disk device 12. Microprocessor
At 17, N% of the transfer amount is calculated, and the calculation result is set in the capacity register 26. The difference between the output address of the write address counter 19 and the output address of the read address counter 22 is calculated by a subtracter 27, and the difference is compared with the content of a capacitance register 26 by a comparator 28. The coincidence output is supplied to the microprocessor 17, and the microprocessor 17 determines that the FiFo buffer 14 is full to the set capacity, and starts reading the FiFo buffer 14, that is, the RAM 25. Until this start, the read address counter 22 does not perform counting and remains at a constant value.
Is written only.

Amount (N%) according to the transfer amount input in this way
When only the prefetching is performed, the reading of the FiFo buffer 14 is started. Therefore, when the transfer amount is large, the capacity value stored in the capacity register 26 increases, and the capacity of the FiFo buffer 14 is expanded. When the transfer amount is small, the capacity of the FiFo buffer 14 decreases.

[Effects of the Invention] As described above, according to the present invention, the capacity of the FiFo buffer is changed in accordance with the amount of one transfer to the magnetic disk device, and the amount of data prefetching in the FiFo buffer 14 is appropriate for the amount of transfer. In the case of a small transfer amount, writing to the magnetic disk device 12 is not delayed, and writing can be performed faster than in the past. Conversely, in the case of a large transfer amount, data shortage does not occur.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a specific example of the variable capacity FiFo buffer 14, and FIG. 3 is a block diagram showing a control device of a conventional magnetic disk device. .

Claims (1)

(57) [Claims] 1. When data of a transfer data amount M is sent from a CPU to a FiFo buffer at a speed Vi, and when the FiFo buffer becomes full, output data of the FiFo buffer is transmitted at a speed Vi.
In the control device of the magnetic disk drive for writing to the magnetic disk at a faster speed Vo, the physical capacity No of the FiFo buffer itself is a shortage Nm determined by the maximum transfer data amount Mm, the speed Vi and the speed Vo at one time. = Mm
(1−Vi / Vo) is selected to be at least larger than the above. For one transfer data amount M (M <Mm), the used capacity N of the FiFo buffer is set to N = M (1−Vi / Vo). A control device for a magnetic disk drive, comprising a capacity setting means for selection.