Hewlett-packard Company

Harold C Ockerse

Gregory Alton Vaughn

Mark E Hodges

Douglas G Keithley

Donald J Fasen

Todd A Fischer

Scott D Bonar

Steven J Jahr

A system and method dynamically allocate memory to a RAM disk. Upon a file transfer to the RAM disk, a device driver determines an amount of memory required by the RAM disk then requests the required amount of memory from a memory manager. As files are deleted from the RAM disk, the memory is released from the RAM disk by informing the memory manager of the addresses of the memory to be released. Sector freelists tracks each cluster of memory allocated to the RAM disk. When a sector becomes inactive, a corresponding bit in a sector freelist indicates the inactive status of the sector. When all of the sectors in a cluster are inactive, the cluster is released for the RAM disk.

Dynamic RAM disk

Dynamically allocable RAM disk

A peripheral device (such as a printer) locates shareable resources on an accessory by using an offset mechanism on the accessory. The offset mechanism includes one or more offset values stored in a first memory location on the accessory. The one or more offset values are indicative of offsets of one or more resources within the accessory memory. The one or more accessory resources are shareable with the peripheral device. A further offset value is stored in a second memory location on the accessory. The further offset value is indicative of an offset for determining the first memory location on the accessory. Additionally, a base address is stored in yet another memory location on the accessory and provides a general reference point for locating the first memory and accessory resources as mapped into the peripheral's memory. In a preferred embodiment, the offset mechanism of the present invention is implemented as an enhanced feature of the PCI Local Bus Specification. For example, the first memory location is disposed in the PCI defined Memory Address Space of the accessory, and the second memory location and base address are both disposed in the PCI defined Configuration Address Space of the accessory. Advantageously, the present invention enables a peripheral device to locate resources on an accessory without knowing in advance where the resources are located on the accessory.

Accessory based resource offset mechanism for a PCI bus in a printer

In a disk drive, servo gain correction, in the presence of servo code signal variations, is achieved by utilizing the servo position signals to produce a servo gain scaling signal which is combined with the servo position signals to produce a corrected servo position signal for controlling the servo. The disk tracks comprise four phases of servo code, either dedicated or sampled servo code. The servo code is conventionally defined by four phases of recorded magnetic dibits, A, B, C, D. Normal, N, [N=(A-B)] and quadrature, Q, [Q=(C-D)], servo position signals are developed from the recorded dibits, either or both of the normal and quadrature signals may be used for controlling the servo. Absolute value signals N and Q are rectified values of the normal N, and quadrature, Q, signals. The absolute value signals are summed to produce a scaling signal, N + Q , and the respective servo signals N and Q are scaled by multiplication with an inverse function ##EQU1## of the scaling signal, N + Q , called the servo gain scaling signal, to produce a corrected servo position signal, N*, or, Q*, respectively defined as ##EQU2## either of which, or the joint use of which, may be employed for controlling the servo system.

Servo gain compensation in a disk drive

A linear or rotary disk memory drive having provision for compensating or cancelling track position syncopation. Due to interference among the magnetic fields of magnetic dibits recorded in and adjacent to a servo code field in a magnetic memory disk, magnetic field intensities are displaced, producing an indication of a track center displaced from the actual track center. A magnetic head tracking such displaced magnetic fields is consequently displaced from track center, which is unacceptable. Four phases of magnetic dibits of servo code are recorded in each of at least four consecutive circumferential frames in a memory disk, in differing servo code formats or patterns of magnetic dibits. Magnetic head servo code signals derived from the magnetic fields of these servo code magnetic dibit patterns are logically processed to produce an AC signal representing track position syncopation which is cancelled by filtering, leaving servo code signals accurately reflecting the position of the magnetic head with respect to a track center.

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Boise, ID, United States of America

Harold C Ockerse