![]() ![]() ![]() With USB 2.0, the 125 us polling interval was critical to how the bus was time-division multiplexed between devices. However, because 3.0 uses point-to-point links, there is no multiplexing to be done and thus the polling interval no longer exists.Īs a result, the latency on packet delivery is much less than with USB 2.0. I suspect that the vast majority of that time is spent in various OS delays, eg the user-space to kernel-space mode switch and the DPC latency within the driver. We are also testing the roundtrip time with the Cypress FX-3, but can not seem to achieve the same results as you did.ĭid you conduct your test with a single packet or with a stream of data and which transfer mode did you use Could you maybe point us in the right direction. I think I just used some simple example code from the Cypress SDK and ran on a Dell laptop probably running Windows XP.Ī device driver may change the interval with small finite adjustments depending on the implementation of host and system software. USB 3.0 adds mechanism for devices to send a Bus Interval Adjustment Message that is used by the host to adjust its 125 s bus interval up to -13.333 s. The host will frequently poll the device and ask for data, and the device may only transmit data once it has been requested by the host. USB 3.0 improves upon this communication model and reduces transmission latency by minimizing polling and also allowing devices to transmit data as soon as it is ready. Provide details and share your research But avoid Asking for help, clarification, or responding to other answers. ![]() Making statements based on opinion back them up with references or personal experience. #Usb overdrive registration code serial.#Usb overdrive registration code for mac os.#Usb overdrive registration code how to. ![]()
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