Fast write/read on NVRAM with Windows
Depending on the USB chipset that you are using, there are a couple of considerations...


From an OS userland point of view, Windows/Linux/OSX will impose a form of ... latency with respect unique commands. Depending on the loading of the OS this could be between 5-10ms if direct driver access is used &amp; upto 20ms if a virtualComms is used. 
Latency timers. USB expects certain sized payloads &amp; if this is not reached there is usually a "latency timer" that permits a timeout to force flushing the RX buffer. This is beneficial if short data packets are being sent.


So... depending on how you are sending the data via USB be it bulk read/write or individual read/write &amp; the size of the payload, you may be running foul of one of these limitations.