Preventing floppy disk data corruption
AssigneeHewlett-Packard Development Company, L.P.
InventorAlexander J Neudeck
Life of this patent
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Abstract
DMA requests from at least one DMA channel with a higher priority than the floppy-disk controller are disabled for at least a portion of a write to floppy DMA operation that includes the transfer of the last byte. This helps ensure that DMA requests generated by the floppy-disk controller will be responded to in under 14 μS preventing an undetected underrun condition on systems with flawed floppy disk controllers from occurring. An estimate of when the last byte of a write to floppy DMA operation is going to be transferred is made. This estimate may be based upon a fixed interval from the start of the write operation. This estimate may also be based upon readings taken from the byte counter and of the DMA controller and the system timer.
Claims44
A method, comprising:
- detecting whether a floppy disk operation is a write;
- and,
- masking DMA requests from at least one DMA channel during said write thereby preventing data corruption, wherein said at least one DMA channel has a higher priority than a DMA channel associated with said floppy disk operation.
An apparatus, comprising:
- a floppy disk controller receiving data via DMA accesses under the control of a DMA controller wherein said DMA controller ignores at least one DMA request line when an underrun error may occur, wherein said at least one DMA request line has a higher priority than a DMA request line associated with said floppy disk controller.
An apparatus, comprising:
- a DMA controller in communication with a floppy disk controller;
- and,
- means for masking at least one DMA request line when a DMA underrun may occur due to an improperly designed floppy disk controller, wherein said at least one DMA request line has a higher priority than a DMA request line associated with said floppy disk controller.
A program storage medium readable by a computer, tangibly embodying a program of instructions executable by a computer to perform method steps, said method steps comprising:
- detecting whether a floppy disk operation is a write;
- and, masking DMA requests from at least one DMA channel during said write thereby preventing data corruption, wherein said at least one DMA channel has a higher priority than a DMA channel associated with said floppy disk operation.
Dependencies are inferred from the claim text.