Apple Inc.

Koninklijke Philips Corporation N.v.

Ati International Srl

Lakshmi Rao

Joseph P Bratt

Kornelis Antonius Vissers

James Battle

Sunny C Huang

Frans Sijstermans

Rudolf H J Bloks

Techniques are disclosed relating to detecting and interjecting a programmed input/output (PIO) operation into a direct memory access (DMA) operation. In one embodiment, an integrated circuit may include a DMA controller that may contain a control circuit, a DMA unit, and a PIO unit. The control circuit may be configured to detect a pending PIO operation during a DMA operation and interject the PIO operation onto a shared path during the same clock cycle as or the first clock cycle following the detection of the pending PIO operation. The DMA operation may consist of multiple single-clock-cycle beats. In one embodiment, a PIO operation may be interjected onto the shared path between beats of a DMA operation, on consecutive clock cycles. At the next clock cycle following the PIO operation, the control circuit may resume the next beat of the DMA operation.

PIO interjection between beats of a DMA operation

The invention is directed to techniques for managing a cache within a processor using one or more machine instructions. The machine instructions may perform one or more operations on the cache. For example, victimize instructions, allocate instructions, and pre-fetch instructions can be executed in the processor as part of cache management. Moreover, these various cache management instructions may be defined by one or more operands that specify memory addresses within main memory, rather than addresses or identifiers that define locations within the cache. For this reason, a programmer may invoke these cache management instructions to direct the management of the cache without knowing the specific location of data within the cache.

Cache management instructions

A prefetch buffer architecture includes a prefetch buffer connected to a memory unit via a global bus. A continue detect unit is also connected to the global bus via a global bus interface. The continue detect unit examines prefetched data words for a predetermined bit pattern indicating the possible presence of a &ldquo;continue&rdquo; command. The continue detect unit may use one or more comparator circuits to compare each prefetched data word with the predetermined bit pattern. Multiple comparator circuits can be used in parallel to simultaneously examine multiple data words. When the continue detect unit determines that a data word contains the predetermined bit pattern, indicating the likely presence of a &ldquo;continue&rdquo; command, the prefetch operation is suspended. The data word likely to contain the &ldquo;continue&rdquo; command is stored in the prefetch buffer until it is called by a decode unit, which decodes the continue command. Once the continue command is decoded, the prefetching operations may resume by prefetching data at the appropriate data address, i.e., the &ldquo;continue&rdquo; address. The continue detect unit may also provide the &ldquo;continue&rdquo; address to a prefetch control unit so that the prefetching operation may be resumed at the proper &ldquo;continue&rdquo; address without waiting for the address to be decoded by the decoding unit.

Prefetch buffer with continue detect

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Sunnyvale, CA, United States of America

Lakshmi Rao