Apparatus and method for efficient transmission of unaligned data
View Patent ↗An apparatus and method to transmit unaligned data over an interface bus while providing the appearance of aligned data transfers to the receiving processor. In a preferred embodiment, an alignment mechanism is provided in the bus interface of the receiving processor to align the data transfers transparent to the receiving processor. The alignment mechanism detects an unaligned transfer in the bus command queue and forms multiple commands of aligned data to send to the processor.
1. A computer system comprising:
a first processor with a first bus interface;
a bus coupled to the first bus interface;
a second bus interface coupled to the bus;
a bus alignment circuit in hardware for the second bus interface that converts data bus commands received from the bus with unaligned data from the first processor to multiple bus commands with aligned data;
wherein the bus alignment circuit sends the multiple bus commands to a second processor coupled to the second bus interface and wherein conversion of the bus commands to aligned data is transparent to the second processor; and
wherein the bus alignment circuit further comprises a command pointer circuit with a command queue address pointer that points to the next command to process and a multiplexer that selects a next command pointer from the command queue address pointer and an incremented command queue address pointer depending on the state of a hold address signal from a state machine.
2. The computer system of claim 1 wherein the bus alignment circuit further comprises a command queue to hold the commands of data packets received over the bus and a data queue to hold data from the data packets.
3. The computer system of claim 1 wherein the bus alignment circuit further comprises a bus alignment detection circuit to detect unaligned commands in the command queue.
4. The computer system of claim 1 wherein the bus alignment circuit further comprises the state machine to reformat unaligned commands into multiple commands with aligned data using packet reformatting logic.
5. A computer system comprising:
a first processor with a first bus interface;
a bus coupled to the first bus interface;
a second bus interface coupled to the bus;
a bus alignment mechanism in the second bus interface that converts data bus commands received from the bus with unaligned data from the first processor to multiple bus commands with aligned data;
wherein the bus alignment mechanism sends the multiple bus commands to a second processor coupled to the second bus interface and wherein the second processor transparently receives the multiple bus commands with aligned data; wherein the bus alignment mechanism comprises a state machine to reformat unaligned commands into multiple commands with aligned data using packet reformatting logic; and wherein the bus alignment mechanism further comprises a command pointer circuit with a command queue address pointer that points to the next command to process and a multiplexer that selects a next command pointer from the command queue address pointer and an incremented command queue address pointer depending on the state of a hold address signal from the state machine.
6. The computer system of claim 5 wherein the bus alignment mechanism further comprises a command queue to hold the bus commands of data packets received over the bus from the first processor and a data queue to hold data from the data packets.
7. The computer system of claim 6 wherein the bus alignment mechanism further comprises a bus alignment detection circuit to detect unaligned commands in the command queue.