Abstract: An apparatus and method for generating 64 bit displacement and immediate values. In a given processor architecture such as the x86 architecture, instructions may conform to a specified instruction format. The instruction format can include a displacement field and an immediate field. The displacement field can include a displacement value of up to 32 bits and the immediate field can include an immediate value of up to 32 bits. In order to generate 64 bit displacement and immediate values, the 32 bit value from the displacement field of an instruction and the 32 bit value from the immediate field of the instruction may be concatenated to generate a 64 bit concatenated value. The concatenated value may be used by an execution core as a 64 bit displacement or immediate value as specified by the instruction.

Abstract: A cache is coupled to receive an input address and a corresponding way prediction. The cache provides output bytes in response to the predicted way (instead of, performing tag comparisons to select the output bytes). Furthermore, a tag may be read from the predicted way and only partial tags are read from the non-predicted ways. The tag is compared to the tag portion of the input address, and the partial tags are compared to a corresponding partial tag portion of the input address. If the tag matches the tag portion of the input address, a hit in the predicted way is detected and the bytes provided in response to the predicted way are correct. If the tag does not match the tag portion of the input address, a miss in the predicted way is detected. If none of the partial tags match the corresponding partial tag portion of the input address, a miss in the cache is determined.

Abstract: A first dynamic logic circuit has an output node on which a scan value is provided during scan. One of one or more second dynamic logic circuits has an input coupled to the output node of the first dynamic logic circuit, and an output of the second dynamic logic circuits is sampled in response to the scan value during scan. In one embodiment, clock generation circuitry may be included which generates a first clock, a second clock, and a third clock. At least one evaluate pulse on the first clock prior is generated prior to sampling the output of the second dynamic logic circuits, the first clock controlling at least the evaluation of the second dynamic logic circuits. The second and third clocks are generated to isolate the output node from inputs to the first dynamic logic circuit responsive to the scan mode signal indicating that scan is active.

Abstract: A cache is coupled to receive an access which includes a cache allocate indication. If the access is a miss in the cache, the cache either allocates a cache block storage location to store the cache block addressed by the access or does not allocate a cache block storage location in response to the cache allocate indication. In one implementation, the cache is coupled to an interconnect with one or more agents. In such an implementation, the cache accesses may be performed in response to transactions on the interconnect, and the transactions include the cache allocate indication. Thus, the source of a cache access specifies whether or not to allocate a cache block storage location in response to a miss by the cache access. The source may use a variety of mechanisms for generating the cache allocate indication.

Abstract: An integrated circuit includes an address register, clocked by the clock signal corresponding to the TAP, used to address a control/status register within the integrated circuit. The address register receives a signal indicating that an address is to be loaded into the address register. A control circuit is coupled to receive the signal and to generate a second signal responsive to the address register being loaded. A shadow register, clocked by the clock signal of the integrated circuit, is coupled to receive the second signal and to load a value from the control/status register addressed by the address loaded into the address register responsive to the second signal. In this manner, a valid value from the addressed register is synchronized in the clock domain of the addressed register. The value for the shadow register may subsequently be synchronized into the clock domain of the TAP, and subsequently transferred out of the integrated circuit via the test interface.

Abstract: An agent may be coupled to receive a clock signal associated with the bus, and may be configured to drive a signal responsive to a first edge (rising or falling) of the clock signal and to sample signals responsive to the second edge. The sampled signals may be evaluated to allow for the driving of a signal on the next occurring first edge of the clock signal. By using the first edge to drive signals and the second edge to sample signals, the amount of time dedicated for signal propagation may be one half clock cycle. Bandwidth and/or latency may be positively influenced. In some embodiments, protocols which may require multiple clock cycles on other buses may be completed in fewer clock cycles. For example, certain protocols which may require two clock cycles may be completed in one clock cycle. In one specific implementation, for example, arbitration may be completed in one clock cycle. Request signals may be driven responsive to the first edge of the clock signal and sampled responsive to the second edge.

Abstract: An apparatus may include at least a first transistor, a second transistor, and a circuit. The first transistor has a first control terminal coupled to receive a first dynamic data signal, and is coupled to a first node. The first transistor drives a first state on the first node responsive to an assertion of the first dynamic data signal. The second transistor is coupled to the first node and has a second control terminal. The second transistor is drives a second state on the first node responsive to a signal on the second control terminal. The circuit is coupled to generate the signal on the second control terminal and is coupled to receive a second dynamic data signal. The second dynamic data signal is a complement of the first dynamic data signal, wherein the circuit is activates the second transistor responsive to an assertion of the second dynamic data signal.

Abstract: Various methods and systems for mapping virtual addresses having more than 32 bits, such as 48 or 64 bits, to physical addresses are disclosed. A processor includes a translation unit that translates or maps a virtual address to a physical address. The translation unit may translate a virtual address to a physical address using either a first or second mapping mechanism (e.g., a first or second plurality of paging tables, with entries respectively having first and second sizes) supporting virtual addresses having at most a first number of bits, such as 32 bits, or a third page mapping mechanism (e.g., a third plurality of page tables) supporting virtual address having more than the first number of bits, such as 48 bits or 64 bits. The translation unit may select the first or second plurality of paging tables depending on the active operating mode of the processor.

Abstract: A ROM or other memory may include two or more partitions and a precharge circuit. Each of the partitions may be coupled to separate sets of output conductors, to which the precharge circuit may be coupled. The precharge circuit may precharge the conductors of the partition to be read, while not precharging the other conductors. In one embodiment, the precharge may be to a voltage representing a binary value. In one implementation, the non-precharged conductors may be held to a predetermined voltage different from the voltage to which the precharged conductors are precharged. The predetermined voltage may represent the opposite binary value to the binary value represented by the precharge voltage. The ROM may also include an output circuit which may, in certain embodiments, comprise a logic circuit which logically combines the signals on respective conductors from each partition to provide output signals from the ROM.

Abstract: An address relocation cache includes a plurality of entries. Each of the plurality of entries is configured to store at least a portion of an input address, at least a portion of an output address to which the input address translates, and a destination identifier corresponding to the output address. An input address may be translated to the output address and the corresponding destination identifier may be obtained concurrently for input addresses which hit in the address relocation cache. If an input address misses in the address relocation cache, a translation corresponding to the address may be located for storing into the address relocation cache. The output address indicated by the translation may be passed through the address map to obtain the destination identifier, and the destination identifier may be stored in the address relocation cache along with the output address.

Abstract: An apparatus includes a buffer configured to store information corresponding to store memory operations and circuitry to detect a load which hits one of the stores represented in the buffer. More particularly, the circuitry may compare the index portion of the load address to the index portions of the store addresses stored in the buffer. If the indexes match and both the load and the store are a hit in the data cache, then the load and store are accessing the same cache line. If one or more bytes within the cache line are updated by the store and read by the load, then the store data is forwarded for the load. In one embodiment, the circuitry speculatively forwards data if the load and store indexes match and the store is a hit in the data cache. Subsequently, when the load is determined to hit/miss in the cache, the forwarding is verified using the load's hit/miss indication.

Abstract: A conditional clock buffer circuit is disclosed. In one embodiment, a conditional clock buffer circuit includes a precharge circuit, a first transistor and a second transistor coupled to the precharge circuit via the first node and the second node, a third transistor coupled to the first transistor and the second transistor. The first transistor may be activated responsive to a condition external to the clock buffer circuit. When the first transistor is activated, an output clock signal driven by the clock buffer circuit may be inhibited.

Abstract: A processor employs a store to load forward (STLF) predictor which may indicate, for dispatching loads, a dependency on a store. The dependency is indicated for a store which, during a previous execution, interfered with the execution of the load. Since a dependency is indicated on the store, the load is prevented from scheduling and/or executing prior to the store. The STLF predictor is trained with information for a particular load and store in response to executing the load and store and detecting the interference. Additionally, the STLF predictor may be untrained (e.g. information for a particular load and store may be deleted) if a load is indicated by the STLF predictor as dependent upon a particular store and the dependency does not actually occur. In one implementation, the STLF predictor records at least a portion of the PC of a store which interferes with the load in a first table indexed by the load PC.

Abstract: A line predictor caches alignment information for instructions. In response to each fetch address, the line predictor provides alignment information for the instruction beginning at the fetch address, as well as one or more additional instructions subsequent to that instruction. The line predictor may include a memory having multiple entries, each entry storing up to a predefined maximum number of instruction pointers and a fetch address corresponding to the instruction identified by a first one of the instruction pointers. Additionally, each entry may include a link to another entry storing instruction pointers to the next instructions within the predicted instruction stream, and a next fetch address corresponding to the first instruction within the next entry. The next fetch address may be provided to the instruction cache to fetch the corresponding instruction bytes.

Abstract: A CAM may include a plurality of CAM cells. Each CAM cell is configured to generate an output indicating if a corresponding input bit and the bit stored in that CAM cell match. A circuit is configured to logically AND the outputs to generate a hit output. A first compare line generator circuit is configured to generate a first pulse responsive to a clock signal and a data signal and a second compare line generator circuit is configured to generate a second pulse responsive to the clock signal and the complement of the data signal. A CAM may include a circuit configured to generate a pulse indicating a hit in an entry of the CAM and a latch circuit configured to capture the pulse responsive to the first clock signal and configured to clear responsive to the second clock signal. A first CAM may store a value in each entry and may further store a compare result.

Abstract: A method and apparatus to ensure DLL locking at a minimum delay is provided. In one embodiment, a DLL circuit includes a phase detector, a counter, a programmable delay line, and a counter control circuit. Upon initialization of the DLL circuit, the counter control circuit is configured to cause the counter to count increment, regardless of the phase relationship between a reference clock signal and the output clock signal. The counter continues incrementing, thereby changing the phase relationship between the reference clock signal and the output clock signal by adjusting the delay of the programmable delay line. This eventually results in a phase lock between the reference clock signal and the output clock signal at a minimum delay. Once the DLL achieves a phase lock between the reference clock signal and the output clock signal, the counter increments or decrements its count in order to maintain or re-acquire a lock.

Abstract: A conditional clock buffer circuit includes a clock output and is coupled to receive a clock input and a condition signal. The conditional clock buffer circuit includes a first circuit coupled to receive the clock input and a second circuit coupled to receive the clock input and the condition signal. The first circuit is configured to generate a first state on the clock output responsive to a first phase of the clock input. The second circuit is configured to conditionally generate a second state on the clock output responsive to the condition signal during a first portion of a second phase of the clock input. In one implementation, one or more of the conditional clock buffer circuits may be included in a clock tree. The clock tree may also include one or more levels of buffering.

Abstract: An agent, in response to a write to a shared block, is configured to initiate a read exclusive transaction on an interface on which the agent communicates. Additionally, the agent is configured to indicate, to a responding agent or agents on the interface, that a data transfer is not required from the responding agent or agents in response to the read exclusive transaction. In one embodiment, the agent indicates to the responding agents that a data transfer is not required in a response phase of the transaction. Specifically, the agent may respond in such a way that the agent indicates that it will provide the data (i.e. that the agent will provide the data to itself). For example, the agent may respond with an exclusive ownership indication. On the interface for such an embodiment, an exclusive ownership response may require that the agent having exclusive access respond with the data.

Abstract: A line predictor caches alignment information for instructions. In response to each fetch address, the line predictor provides information for the instruction beginning at the fetch address, as well as alignment information for up to one or more additional instructions subsequent to that instruction. The line predictor may include a memory having multiple entries, each entry storing up to a predefined maximum number of instruction pointers and a fetch address corresponding to the instruction identified by a first one of the instruction pointers. Since the line predictor provides alignment information from one entry per fetch, the line predictor may provide a flow control mechanism for the initial portion of the pipeline within a microprocessor. Each entry may store combinations of instructions which the hardware within the pipeline may handle without creating stalls resulting from the combinations.

Abstract: An adaptive retry mechanism may record latencies of recent transactions (e.g. the first data transfer latency), and may select a retry latency from two or more retry latencies. The retry latency may be used for a transaction, and may specify a point in time during the transaction at which the transaction is retried if the first data transfer has not yet occurred. In one implementation, the set of retry latencies includes a minimum retry latency, a nominal retry latency, and a maximum retry latency. The nominal retry latency may be set slightly greater than the expected latency of transactions in the system. The minimum retry latency may be less than the nominal retry latency and the maximum retry latency may be greater than the nominal retry latency. If latencies greater than the nominal retry latency but less than the maximum retry latency are being experienced, the maximum retry latency may be selected.