Abstract: A communications bus for a digital device includes a credit-based flow control mechanism, in which a sending component maintains a local record of its credits. Credits are returned to the sender by pulsing a single-bit credit return line. A separate mechanism provides a count of available credits from the receiver, the separate mechanism not necessarily being current. The local record is compared to the count of credits from the separate mechanism over a pre-determined time interval, failure of the two values to agree at any time during the interval indicating a probable credit discrepancy. A credit discrepancy is confirmed, preferably by suspending certain bus activity for a sufficiently long period to account for any delay in propagating credit value changes, and re-comparing the values.

Abstract: A communications bus for a digital device includes a credit-based flow control mechanism, in which a sending component maintains a local record of its credits. Credits are returned to the sender by pulsing a single-bit credit return line. A separate mechanism provides a count of available credits from the receiver, the separate mechanism not necessarily being current. The local record is compared to the count of credits from the separate mechanism over a pre-determined time interval, failure of the two values to agree at any time during the interval indicating a probable credit discrepancy. A credit discrepancy is confirmed, preferably by suspending certain bus activity for a sufficiently long period to account for any delay in propagating credit value changes, and re-comparing the values.

Abstract: A computer machine instruction is fetched and executed, the machine instruction having a signed field value wherein the signed field value comprises contiguous bit positions 1-N consisting of a contiguous most significant value contiguous with a contiguous embedded sign field, the embedded sign field contiguous with a contiguous least significant value. Preferably, the sign field is one bit, the contiguous most significant value comprises bit position N and the least significant value comprises bit position 1 wherein N is the least significant bit of the most significant value.

Abstract: A control mechanism for data bus communications employs channels to which bus transactions are assigned, each channel having independent flow control. The control mechanism enforces an ordering algorithm among channels, whereby at least some transactions may pass other transactions. Channel attributes are programmable to vary the ordering conditions. Preferably, each channel is allocated its own programmable buffer area. The control mechanism independently determines, for each channel, whether buffer space is available and enforces flow control independently for each channel accordingly. Flow control is preferably credit-based, credits representing buffer space or some other capacity of a receiver to receive data. Preferably, the flow control mechanism comprises a central interconnect module controlling internal communications of an integrated circuit chip.

Abstract: An integrated circuit chip includes multiple functional components and a central interconnect module providing communication among the functional components. The central interconnect module includes a buffer which is shared by the sending and receiving components. Preferably, some components perform different functions and communicate with the central interconnect via a common architectural interface. Preferably, each sender is allocated respective credits representing ability of the receiver to receive data (e.g., available buffer space), and the sender can transmit data if it has credits. Credits are decremented when the sender sends data, and returned by the receiver when is again able to receive. The use of a common central interconnect module with a shared buffer reduces buffer requirements and provides a low-overhead path for transferring data within the integrated circuit chip.

Abstract: A communications bus for a digital device includes a credit-based flow control mechanism, in which a sending component maintains a local record of its credits. Credits are returned to the sender by pulsing a single-bit credit return line. A separate mechanism provides a count of available credits from the receiver, the separate mechanism not necessarily being current. The local record is compared to the count of credits from the separate mechanism over a pre-determined time interval, failure of the two values to agree at any time during the interval indicating a probable credit discrepancy. A credit discrepancy is confirmed, preferably by suspending certain bus activity for a sufficiently long period to account for any delay in propagating credit value changes, and re-comparing the values.

Abstract: An integrated circuit chip includes multiple functional components and a central interconnect (CI) module. Each functional component communicates with the CI module via a respective internal bus sharing a common architecture which does not dictate any particular data alignment. The chip architecture defines an alignment mechanism within the CI module, which performs any required alignment of transmitted data. Alignment mechanism design parameters can be varied to accommodate different alignment domains of different functional components. Preferably, the common bus architecture supports multiple internal bus widths, the CI module performing any required bus width conversion. Preferably, for certain transactions not containing a data address, correct alignment is obtained by placing restrictions on transaction size and boundaries, and duplicating certain data on different alignment boundaries.

Abstract: A computer architecture that provides the definition of a 20 bit signed displacement value used to form the operand storage address.

Abstract: A method of pre-aligning data for storage during instruction execution improves performance by eliminating the cycles otherwise required for data alignment. The method can convert data between ASCII and Packed Decimal format, and between Unicode Basic Latin and Packed Decimal format. Conversion to Packed Decimal format is needed for decimal hardware in a microprocessor designed to generate decimal results. Converting from Packed Decimal to ASCII and Unicode Basic Latin is necessary to report Decimal Arithmetic results in a required format for the application program. To further improve performance, all available write ports in the fixed point unit (FXU) are utilized to reduce the number of cycles necessary to store results. To prevent data fetching of the unused destination data from slowing down instruction execution, the destination locations are tested for storage access exceptions, but the data for these operands are not actually fetched.

Abstract: Disclosed is a method and apparatus providing the capability to prevent particular branches from being written into the BTB, thereby making them non-predictable. By making certain branches only detectable at decode time frame, branch prediction can completely run asynchronous of decode. By allowing branch prediction logic to cover as wide a range of branches as possible, the efficiency of fetching of branch targets way before the branch itself achieves a higher level of precision. This increased level of precision eliminates pipeline stalls between branches and targets where prior concerns of creating data integrity within the pipeline of a microprocessor existed.